KERNEL- LINUX
The Linux kernel is a Unix-like computer operating system kernel. The Linux kernel is a widely used operating system kernel world-wide; the Linux operating system is based on it and deployed on both traditional computer systems, usually in the form of Linux distributions,and on embedded devices such as routers. The Android operating system for tablet computers and smartphones is also based atop the Linux kernel.
The Linux kernel was initially conceived and created in 1991 by Finnish computer science student Linus Torvalds,for his personal computer and with no cross-platform intentions, but has since expanded to support a huge array of computer architectures, more than any other operating system or kerneL.Linux rapidly attracted developers and users who adapted code from other free software projects for use with the new operating system.The Linux kernel has received contributions from nearly 12,000 programmers from more than 1,200 companies, including some of the largest software and hardware vendors.
The Linux kernel API, the application programming interface (API) through which user programs interact with the kernel, is meant to be very stable and to not break userspace programs (some programs, such as those with GUIs, rely on other APIs as well). As part of the kernel's functionality, device drivers control the hardware; "mainlined" device drivers are also meant to be very stable. However, the interface between the kernel and loadable kernel modules (LKMs), unlike in many other kernels and operating systems, is not meant to be very stable by design.
The Linux kernel, developed by contributors worldwide, is a prominent example of free and open source software.Day-to-day development discussions take place on the Linux kernel mailing list (LKML). The Linux kernel is released under the GNU General Public License version 2 (GPLv2),with some firmware images released under various non-free licenses.
Contents
1 History
1.1 Tanenbaum–Torvalds debate
1.2 Popularity
2 Legal aspects
2.1 Licensing terms
2.1.1 GPL version 3
2.2 Loadable kernel modules
2.2.1 Kernel modules
2.3 Firmware binary blobs
2.4 Trademark
2.5 SCO litigation
3 Architecture
3.1 Programming language
3.2 Compiler compatibility
3.3 Interfaces
3.3.1 Kernel-to-userspace API
3.3.2 Kernel-to-userspace ABI
3.3.3 In-kernel API
3.3.4 In-kernel ABI
3.4 Technical features
3.4.1 Preemption
3.4.2 Portability
3.4.3 Kernel panic and oopses
3.5 Security
3.6 Feature history
4 Development
4.1 Estimated cost to redevelop
4.2 Development model
4.2.1 Relation with Linux distributions
4.3 Maintenance
4.3.1 Releases before 2.6.0
4.3.2 2.6.x.y releases
4.3.3 3.x.y releases
4.3.4 4.x.y releases
4.4 Revision control
4.5 Version numbering
4.6 Timeline
4.7 Variants
History
In April 1991, Linus Torvalds, a 21-year-old student at the University of Helsinki, Finland started working on some simple ideas for an operating system. He started with a task switcher in Intel 80386 assembly language and a terminal driver. On 25 August 1991, Torvalds posted the following to comp.os.minix, a newsgroup on Usenet:
I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu) for 386(486) AT clones. This has been brewing since April, and is starting to get ready. I'd like any feedback on things people like/dislike in minix, as my OS resembles it somewhat (same physical layout of the file-system (due to practical reasons) among other things).
I've currently ported bash(1.08) and gcc(1.40), and things seem to work. This implies that I'll get something practical within a few months Yes - it's free of any minix code, and it has a multi-threaded fs. It is NOT portable (uses 386 task switching etc), and it probably never will support anything other than AT-harddisks, as that's all I have :-(.
It's mostly in C, but most people wouldn't call what I write C. It uses every conceivable feature of the 386 I could find, as it was also a project to teach me about the 386. As already mentioned, it uses a MMU, for both paging (not to disk yet) and segmentation. It's the segmentation that makes it REALLY 386 dependent (every task has a 64Mb segment for code & data - max 64 tasks in 4Gb. Anybody who needs more than 64Mb/task - tough cookies). Some of my "C"-files (specifically mm.c) are almost as much assembler as C. Unlike minix, I also happen to LIKE interrupts, so interrupts are handled without trying to hide the reason behind them.
After that, many people contributed code to the project. Early on, the MINIX community contributed code and ideas to the Linux kernel. At the time, the GNU Project had created many of the components required for a free operating system, but its own kernel, GNU Hurd, was incomplete and unavailable. The BSD operating system had not yet freed itself from legal encumbrances. Despite the limited functionality of the early versions, Linux rapidly accumulated developers and users.
By September 1991, Linux version 0.01 was released on the FTP server (ftp.funet.fi) of the Finnish University and Research Network (FUNET). It had 10,239 lines of code. In October 1991, Linux version 0.02 was released.
In December 1991, Linux 0.11 was released. This version was the first to be self-hosted - Linux 0.11 could be compiled by a computer running Linux 0.11. When he released version 0.12 in February 1992, Torvalds adopted the GNU General Public License (GPL) over his previous self-drafted license, which had not permitted commercial redistribution.
A newsgroup known as alt.os.linux was started, and on 19 January 1992, the first post to alt.os.linux was made.On 31 March 1992, alt.os.linux became comp.os.linux.
The X Window System was soon ported to Linux. In March 1992, Linux version 0.95 was the first to be capable of running X. This large version number jump (from 0.1x to 0.9x) was due to a feeling that a version 1.0 with no major missing pieces was imminent. However, this proved to be somewhat overoptimistic, and from 1993 to early 1994, 15 development versions of version 0.99 appeared.
On 14 March 1994, Linux 1.0.0 was released, with 176,250 lines of code. In March 1995, Linux 1.2.0 was released (310,950 lines of code).
Version 2 of Linux, released on 9 June 1996, was followed by additional major versions under the version 2 header:
25 January 1999 - Linux 2.2.0 was released (1,800,847 lines of code).
18 December 1999 - IBM mainframe patches for 2.2.13 were published, allowing Linux to be used on enterprise-class machines.
4 January 2001 - Linux 2.4.0 was released (3,377,902 lines of code).
17 December 2003 - Linux 2.6.0 was released (5,929,913 lines of code).
Starting in 2004, the release process changed and new kernels started coming out on a regular schedule every 2–3 months, numbered 2.6.0, 2.6.1, up through 2.6.39.
On 21 July 2011 Linus Torvalds announced the release of Linux 3.0: "Gone are the 2.6.<bignum> days".The version bump is not about major technological changes when compared to Linux 2.6.39;it marks the kernel's 20th anniversary.The time-based release process remained the same.
As of 2013, the Linux 3.10 release had 15,803,499 lines of code.
Tanenbaum–Torvalds debate
The fact that Linux is a monolithic kernel rather than a microkernel was the topic of a debate between Andrew S. Tanenbaum, the creator of MINIX, and Linus Torvalds.The debate, started in 1992 on the Usenet discussion group comp.os.minix, was about Linux and kernel architecture in general.Tanenbaum argued that microkernels are superior to monolithic kernels and that therefore Linux is obsolete. Unlike traditional monolithic kernels, device drivers in Linux are easily configured as loadable kernel modules and are loaded or unloaded while running the system. This subject was revisited on 9 May 2006,and on 12 May 2006 Tanenbaum wrote a position statement.
Popularity
The huge rise in popularity of the Android operating system, which includes the Linux kernel, has made the kernel the most popular choice for mobile devices, rivaling the installed base of all other operating systems. Including previous years, three billion Android smartphones were estimated to have been sold by the end of 2014.
Most consumer routers also use the Linux kernel,as do a wide variety of other devices, such as servers, smart TVs, and other non-Android embedded systems. However, the kernel's use in traditional (non-server) desktop Linux varieties is still low in comparison to other operating systems.
Legal aspects
Licensing terms
Initially, Torvalds released Linux under a license which forbade any commercial use.This was changed in version 0.12 to the GNU General Public License (GPL).This license allows distribution and sale of possibly modified and unmodified versions of Linux but requires that all those copies be released under the same license and be accompanied by the complete corresponding source code.
Torvalds has described licensing Linux under the GPL as the "best thing I ever did."
GPL version 3
Currently, Linux is licensed only under version 2 of the GPL,without offering the licensee the option to choose "any later version", and there is some debate over how easily it could be changed to use later GPL versions such as version 3 (and whether this is even desirable).Torvalds himself specifically indicated upon the release of version 2.4.0 that his own code is only under version 2.However, the terms of the GPL state that if no version is specified, then any version may be used, and Alan Cox pointed out that very few other Linux contributors have specified a particular version of the GPL.In September 2006, a survey of 29 key kernel programmers indicated 28 preferred GPLv2 to the then-current GPLv3 draft. Torvalds commented, "I think a number of outsiders... believed that I personally was just the odd man out, because I've been so publicly not a huge fan of the GPLv3."
Loadable kernel modules
It is debated whether loadable kernel modules (LKMs) are to be considered derivative works under copyright law, and thereby fall under the terms of the GPL.
Torvalds has stated his belief that LKMs using only a limited, "public" subset of the kernel interfaces can sometimes be non-derived works, thus allowing some binary-only drivers and other LKMs that are not licensed under the GPL.A very good example for this is the usage of dma_buf by the proprietary Nvidia graphics drivers. dma_buf is a recent kernel feature (like the rest of the kernel, it is licensed under the GPL) that allows multiple GPUs to quickly copy data into each other's framebuffers.One possible use case would be Nvidia Optimus that pairs a fast GPU with an Intel integrated GPU, where the Nvidia GPU writes into the Intel framebuffer when it is active. But, Nvidia cannot use this infrastructure because it uses a technical means to enforce the rule that it can only be used by LKMs that are also GPL. Alan Cox replied on LKML, rejecting a request from one of their engineers to remove this technical enforcement from the API.Not all Linux kernel contributors agree with this interpretation, however, and even Torvalds agrees that many LKMs are clearly derived works, and indeed he writes that "kernel modules ARE derivative 'by default'".
On the other hand Torvalds has also said that "one gray area in particular is something like a driver that was originally written for another operating system (i.e. clearly not a derived work of Linux in origin). THAT is a gray area, and _that_ is the area where I personally believe that some modules may be considered to not be derived works simply because they weren't designed for Linux and don't depend on any special Linux behaviour."Proprietary graphics drivers, in particular, are heavily discussed. Ultimately, it is likely that such questions can only be resolved by a court.
Kernel modules
Network
Netlink
Network scheduler
Netfilter and nftables (alternatives for other kernels are e.g. PF developed by OpenBSD, NPF developed by NetBSD)
Comparison of open-source wireless drivers
Graphics and general-purpose computing on graphics processing units
Direct Rendering Manager (DRM)
Graphics Execution Manager (GEM)
Free and open-source device drivers: graphics
Sound
Advanced Linux Sound Architecture (ALSA)
Free and open-source device drivers: audio
Input
evdev
Firmware binary blobs
One point of licensing controversy is Linux's use of firmware "binary blobs" to support several hardware devices. These files are under a variety of licenses, many of them restrictive and their exact underlying source code is usually unknown.In the year 2002 Richard Stallman stated why, in his point of view, such blobs make Linux partially non-free software, and that distributing Linux "violates the GPL" (which requires "complete corresponding source code" to be available).In 2008 Free Software Foundation Latin America started a project, Linux-libre, to create a completely free kernel without proprietary objects, which is used by some completely free distributions, such as those endorsed by the Free Software Foundation.On 15 December 2010 the Debian Project announced that the next Debian stable version would come with a kernel "stripped of all non-free firmware bits".This policy was continued with the sequel release of Debian 7 "Wheezy".
Trademark
Linux is a registered trademark of Linus Torvalds in the United States and some other countries. This is the result of an incident in which William Della Croce, Jr., who was not involved in the Linux project, trademarked the name and subsequently demanded royalties for its use.Several Linux backers retained legal counsel and filed suit against Della Croce. The issue was settled in August 1997 when the trademark was assigned to Linus Torvalds.
SCO litigation
In March 2003, the SCO Group (SCO) filed a lawsuit against IBM claiming that IBM had violated copyrights that SCO claimed to hold over the Unix source code, by contributing portions of that code to Linux. Additionally, SCO sent letters to a number of companies warning that their use of Linux without a license from SCO may be a violation of copyright law, and claimed in the press that they would be suing individual Linux users. IBM then promised to defend its Linux customers on their behalf. This controversy has generated lawsuits by SCO against Novell, DaimlerChrysler (partially dismissed in July 2004), and AutoZone, and retaliatory lawsuits by Red Hat and others against SCO.
In early 2007, SCO filed the specific details of the purported copyright infringement. Despite previous claims that SCO was the rightful owner of 1 million lines of code, they specified 326 lines of code, most of which were uncopyrightable.In August 2007, the court in the Novell case ruled that SCO did not actually own the Unix copyrights to begin with,though the Tenth Circuit Court of Appeals ruled in August 2009 that the question of who owned the copyright properly remained for a jury to answer.The jury case was decided on 30 March 2010 in Novell's favour.
Architecture
Map of the Linux kernel
Linux kernel supports various hardware architectures, providing a common platform for running free, open-source and proprietary software.
See also: vmlinux
Linux kernel is a monolithic kernel. Device drivers and kernel extensions run in kernel space (ring 0 in many CPU architectures), with full access to the hardware, although some exceptions run in user space, for example filesystems based on FUSE. The graphics system most people use with Linux does not run within the kernel, in contrast to that found in Microsoft Windows. Unlike standard monolithic kernels, device drivers are easily configured as modules, and loaded or unloaded while running the system. Also unlike standard monolithic kernels, device drivers can be pre-empted under certain conditions. This latter feature was added to handle hardware interrupts correctly, and to improve support for symmetric multiprocessing. By choice, the Linux kernel has no Binary Kernel Interface.
The hardware is also incorporated into the file hierarchy. Device drivers interface to user applications via an entry in the /dev or /sys directories.Process information as well is mapped to the file system through the /proc directory.
Linux kernel supports true preemptive multitasking (both in user mode and kernel mode), virtual memory, shared libraries, demand loading, shared copy-on-write executables (via KSM), memory management, the Internet protocol suite, and threading.
Various layers within Linux, also showing separation between the userland and kernel space
User mode User applications For example, bash, LibreOffice, Apache OpenOffice, Blender, 0 A.D., Mozilla Firefox, etc.
Low-level system components: System daemons:
systemd, runit, logind, networkd, soundd... Windowing system:
X11, Wayland, Mir, SurfaceFlinger (Android) Other libraries:
GTK+, Qt, EFL, SDL, SFML, FLTK, GNUstep, etc. Graphics:
Mesa 3D, AMD Catalyst, ...
C standard library open(), exec(), sbrk(), socket(), fopen(), calloc(), ... (up to 2000 subroutines)
glibc aims to be POSIX/SUS-compatible, uClibc targets embedded systems, bionic written for Android, etc.
Kernel mode Linux kernel stat, splice, dup, read, open, ioctl, write, mmap, close, exit, etc. (about 380 system calls)
The Linux kernel System Call Interface (SCI, aims to be POSIX/SUS-compatible)
Process scheduling
subsystem IPC
subsystem Memory management
subsystem Virtual files
subsystem Network
subsystem
Other components: ALSA, DRI, evdev, LVM, device mapper, Linux Network Scheduler, Netfilter
Linux Security Modules: SELinux, TOMOYO, AppArmor, Smack
Hardware (CPU, main memory, data storage devices, etc.)
Programming language
The Linux kernel is written in the version of the C programming language supported by GCC (which has introduced a number of extensions and changes to standard C), together with a number of short sections of code written in the assembly language (in GCC's "AT&T-style" syntax) of the target architecture. Because of the extensions to C it supports, GCC was for a long time the only compiler capable of correctly building the Linux kernel.
Compiler compatibility
GCC is the default compiler for the Linux kernel source. In 2004, Intel claimed to have modified the kernel so that its C compiler also was capable of compiling it.There was another such reported success in 2009 with a modified 2.6.22 version of the kernel.
Since 2010, effort has been underway to build the Linux kernel with Clang, an alternative compiler for the C language;as of 12 April 2014, the official kernel could almost be compiled by Clang.The project dedicated to this effort is named LLVMLinux after the LLVM compiler infrastructure upon which Clang is built.LLVMLinux does not aim to fork either the Linux kernel or the LLVM, therefore it is a meta-project composed of patches that are eventually submitted to the upstream projects. By enabling the Linux kernel to be compiled by Clang, which, among other advantages, is known for its fast compilation times against GCC, the kernel developers may benefit from a faster workflow due to shorter compilation times.
Interfaces
Main articles: Linux kernel interfaces and Interfaces of the Linux kernel (Category)
This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2015)
Four interfaces are distinguished: two internal to the kernel, and two between the kernel and userspace.
At XDC2014, Alex Deucher from AMD announced the unified kernel-mode driver.The proprietary Linux graphic driver, libGL-fglrx-glx, will share the same DRM infrastructure with Mesa 3D. As there is no stable in-kernel ABI, AMD had to constantly adapt the former binary blob used by Catalyst.
Conformance to standards is a general policy for the Linux kernel's internals. Another rule is that a kernel component is not accepted into the Linux kernel mainline if there is only proprietary user-space software using that component.
Kernel-to-userspace API
Source code portability ensures that a C program written by conforming to a standard can be successfully compiled and run on any system that also conforms to the same standard. The relevant standards, aiming to achieve source code portability of programs, that the development of the Linux kernel, the GNU C Library, and associated utilities tries to adhere to, are POSIX and the Single UNIX Specification. However, as of February 2014, no Linux distributions are branded as "UNIX" by The Open Group, mainly because of the costs of the conformance testing.
The Linux kernel API of the Linux kernel, representing the kernel's system call interface, is composed of the available system calls.
Kernel-to-userspace ABI
Binary portability shall guarantee that any program once compiled for a given hardware platform, can be run in its compiled form on any other hardware platform that conforms to the standard. Binary portability is an essential requirement for the commercial viability of independent software vendor (ISV) applications built for the operating systems based on the Linux kernel. Binary compatibility is much more demanding than source code portability; as of February 2014, the only standard concerning itself with binary compatibility is the Linux Standard Base (LSB).
In-kernel API
There are a couple of kernel internal APIs utilized between the different subsystems and subsystems of subsystems. Some of them have been kept stable over several releases, other have not. There are no guarantees regarding the in-kernel APIs. Maintainers and contributors are free to augment or change them at any time.
Examples of in-kernel APIs include software frameworks/APIs for the following classes of device drivers:
Video4Linux – for video capture hardware
Advanced Linux Sound Architecture – for sound cards
New API – for network interface controllers
Direct Rendering Manager – for graphics accelerators
KMS driver – for display controllers
mac80211 – for wireless network interface controllers
WEXT – for wireless network interface controllers (obsolete).
In-kernel ABI
Strong interests in defining and maintaining a stable in-kernel ABI over several releases have been voiced repeatedly over time by parties, e.g. hardware manufactures, writing proprietary kernel modules and distributing binary-only software, e.g. device drivers.
By explicit choice the Linux kernel does not maintain a stable in-kernel ABI. The reasons are purely technical and not philosophical. Due to the absence of an in-kernel ABI that has to be kept stable over releases, the Linux kernel can keep a much higher rate of development.
Technical features
Preemption
The position of I/O schedulers within various layers of the Linux kernel's I/O stack.
The Linux kernel provides preemptive scheduling under certain conditions. Until kernel version 2.4, only user processes were preemptive, i.e., in addition to time quantum expiration, an execution of current process in user mode would be interrupted if higher dynamic priority processes entered TASK_RUNNING state.Toward 2.6 series of the Linux kernel, an ability to interrupt a task executing kernel code was added, although with that not all sections of the kernel code can be preempted.
The Linux kernel contains different scheduler classes.By default the kernel uses a scheduler mechanism called the Completely Fair Scheduler introduced in the 2.6.23 version of the kernel.Internally this default-scheduler class is also known as SCHED_OTHER, but the kernel also contains two real-time scheduling classes named SCHED_FIFO (realtime first-in-first-out) and SCHED_RR (realtime round-robin) both of which take precedence over the default class.
Through the use of the real-time Linux kernel patch PREEMPT_RT, support for full preemption of critical sections, interrupt handlers, and "interrupt disable" code sequences can be supported.Partial mainline integration of the real-time Linux kernel patch already brought some functionality to the kernel mainline.Preemption improves latency, increases responsiveness, and makes Linux more suitable for desktop and real-time applications. Older versions of the kernel had a so-called big kernel lock for synchronization across the entire kernel, which was finally removed by Arnd Bergmann in 2011.
Additional scheduling policy known as SCHED_DEADLINE, implementing the earliest deadline first algorithm (EDF), was added in kernel version 3.14, released on 30 March 2014.
Portability
An iPod booting iPodLinux
While not originally designed to be portable,Linux is now one of the most widely ported operating system kernels, running on a diverse range of systems from the ARM architecture to IBM Z/Architecture mainframe computers. The first port beyond Linux's original 386 architecture was to the Motorola 68000 platform by Amiga users, but to do this port they replaced major parts of the kernel, leading Torvalds to call it a fork and a "Linux-like operating system".With this experience in mind, Torvalds led a major restructure of the kernel code to facilitate the next port effort, to the DEC Alpha AXP platform, and support both 386 and Alpha in a single source tree.
Linux runs as the main operating system on IBM's Blue Gene and other fastest supercomputers. As of November 2014, the Linux OS family has a 97% share of all systems on the TOP500 supercomputers list.Linux has also been ported to various handheld devices such as TuxPhone, Apple's iPod and iPhone.Some operating systems developed for mobile phones use modified versions of the Linux kernel, including Google Android, Firefox OS, HP webOS, and Nokia Maemo.
Kernel panic and oopses
An example of Linux kernel panic
Main articles: Kernel panic and Linux kernel oops
In Linux, a "panic" is an unrecoverable system error detected by the kernel, as opposed to similar errors detected by user space code. It is possible for kernel code to indicate such a condition by calling the panic function located in the header file sys/system.h. However, most panics are the result of unhandled processor exceptions in kernel code, such as references to invalid memory addresses. These are typically indicative of a bug somewhere in the call chain leading to the panic. They can also indicate a failure of hardware, such as a failed RAM cell or errors in arithmetic functions in the processor caused by a processor bug, overheating/damaged processor, or a soft error.
A report of a non-fatal bug in the kernel is called an "oops"; such deviations from correct behavior of the Linux kernel may allow continued operation with compromised reliability.These crash reports are automatically collected and can be sent upstream by various software, such as kerneloops,ABRT (Fedora)and apport (Ubuntu). KernelOops.org collected these reports and published statistics on their website.
Security
Computer security is a much-publicized topic in relation to the Linux kernel, because a large portion of the kernel bugs can present potential security flaws as they may allow for privilege escalation or create denial-of-service attack vectors. Over the years, numerous such flaws were found and fixed in the Linux kernel.New security features are continuously implemented to address computer insecurity issues in the Linux kernel.
Critics have accused kernel developers of covering up security flaws or at least not announcing them. In response, in 2008, Linus Torvalds replied, "I personally consider security bugs to be just 'normal bugs'. I don't cover them up, but I also don't have any reason what-so-ever to think it's a good idea to track them and announce them as something special...one reason I refuse to bother with the whole security circus is that I think it glorifies—and thus encourages—the wrong behavior. It makes 'heroes' out of security people, as if the people who don't just fix normal bugs aren't as important. In fact, all the boring normal bugs are way more important, just because there's a lot more of them. I don't think some spectacular security hole should be glorified or cared about as being any more 'special' than a random spectacular crash due to bad locking."
At times, bugs have been corrected in Linux before other systems. In May 2012, a difference between the implementations of the SYSRET instruction in AMD and Intel processors was found to cause vulnerabilities in major systems such as Windows, FreeBSD, XenServer, and Solaris. The issue had been fixed in the Linux kernel since 2006.
Raw hardware devices are protected from direct access, and the file system has an inbuilt security system giving individual access to files on three levels, user only, group membership, and world access.
Long-term releases with constant security updates are also available for many Linux distributions. Rebootless security updates can even be applied to the kernel by using technologies such as ksplice, kpatch and kGraft.
Feature history
Version 1.0 of the Linux kernel was released on 14 March 1994.This release of the Linux kernel only supported single-processor i386-based computer systems. Portability became a concern, and so version 1.2 (released 7 March 1995)gained support for computer systems using processors based on the Alpha, SPARC, and MIPS architectures.
Version 2.0 was released on 9 June 1996.There were 41 releases in the series. The major feature of 2.0 was SMP support (that is, support for multiple processors in a single system) and support for more types of processors.
Version 2.2, released on 20 January 1999,removed the global spinlock and provided improved SMP support, added support for the m68k and PowerPC architectures, and added new file systems (including read-only support for Microsoft's NTFS).
Version 2.4.0, released on 4 January 2001,contained support for ISA Plug and Play, USB, and PC Cards.It also included support for the PA-RISC processor from Hewlett-Packard. Development for 2.4.x changed a bit in that more features were made available throughout the duration of the series, including: support for Bluetooth, Logical Volume Manager (LVM) version 1, RAID support, InterMezzo and ext3 file systems.
Version 2.6.0 was released on 17 December 2003.The development for 2.6.x changed further towards including new features throughout the duration of the series. Among the changes that have been made in the 2.6 series are: integration of µClinux into the mainline kernel sources, PAE support, support for several new lines of CPUs, integration of ALSA into the mainline kernel sources, support for up to 232 users (up from 216), support for up to 229 process IDs (64-bit only, 32-bit arches still limited to 215),substantially increased the number of device types and the number of devices of each type, improved 64-bit support, support for file systems which support file sizes of up to 16 terabytes, in-kernel preemption, support for the Native POSIX Thread Library (NPTL), User-mode Linux integration into the mainline kernel sources, SELinux integration into the mainline kernel sources, InfiniBand support, and considerably more. Also notable are the addition of several file systems throughout the 2.6.x releases: FUSE, JFS, XFS, ext4 and more. Details on the history of the 2.6 kernel series can be found in the ChangeLog files on the 2.6 kernel series source code release area of kernel.org.
Version 3.0 was released on 22 July 2011.On 30 May 2011, Torvalds announced that the big change was "NOTHING. Absolutely nothing." and asked "...let's make sure we really make the next release not just an all new shiny number, but a good kernel too." After the expected 6–7 weeks of the development process, it would be released near the 20th anniversary of Linux.
In December 2012, Torvalds decided to reduce kernel complexity by removing support for i386 processors, making the 3.7 kernel series the last one still supporting the original processor The same series unified support for the ARM processor.
Version 3.11, released on 2 September 2013,adds many new features such as new O_TMPFILE flag for open(2) to reduce temporary file vulnerabilities, experimental AMD Radeon dynamic power management, low-latency network polling, and zswap (compressed swap cache).
Development
The kernel changes made in year 2007 have been submitted by no less than 1900 developers – but there may be a lot more because developers working in teams usually count as one. It is generally assumed that the community of Linux kernel developers is composed by 5000 or 6000 members; also, as of 2013, the 3.10 release of the Linux kernel had 15,803,499 lines of code. Without smart project management, it would not be possible to maintain development of such a large codebase.
Instead of a roadmap, there are technical guidelines. Instead of a central resource allocation, there are persons and companies who all have a stake in the further development of the Linux kernel, quite independently from one another: People like Linus Torvalds and I don’t plan the kernel evolution. We don’t sit there and think up the roadmap for the next two years, then assign resources to the various new features. That’s because we don’t have any resources. The resources are all owned by the various corporations who use and contribute to Linux, as well as by the various independent contributors out there. It’s those people who own the resources who decide...
—Andrew Morton, 2005
Linux is evolution, not intelligent design
—Linus Torvalds, 2005
By this statement it is meant that evolution often does odd (and "sub-optimal") things exactly because it does incremental changes which do not break at any point. As a result, any released version of the Linux kernel is fully usable, even if, for example, device drivers do not support all features of the hardware they are written for.
The conceptual architecture of the Linux kernel has proved its success, while essential factors for this success were the provision for the organization of developers, and the provision for system extensibility. The Linux kernel's architecture was required to support a many independent volunteer developers, which suggested that the system portions that require the most development—?the hardware device drivers and the file and network protocols—?be implemented in an extensible fashion. The Linux kernel's architecture chose to make these systems extensible using a data abstraction technique – each hardware device driver is implemented as a separate module that supports a common interface. In this way, a single developer can add a new device driver, with minimal interaction required with other developers of the Linux kernel.
Another important extension to the Linux kernel is the addition of more supported hardware platforms. The architecture of the system supports this extensibility by separating all hardware-specific code into distinct modules within each subsystem. In this way, a small group of developers can implement a port of the Linux kernel to a new hardware architecture by re-implementing only the machine-specific portions of the kernel.
Estimated cost to redevelop
The cost to redevelop the Linux kernel version 2.6.0 in a traditional proprietary development setting has been estimated to be US$612 million (€467M, £394M) in 2004 prices using the COCOMO man-month estimation model.In 2006, a study funded by the European Union put the redevelopment cost of kernel version 2.6.8 higher, at €882M ($1.14bn, £744M).
This topic was revisited in October 2008 by Amanda McPherson, Brian Proffitt and Ron Hale-Evans. Using David A. Wheeler's methodology, they estimated redevelopment of the 2.6.25 kernel now costs $1.3bn (part of a total $10.8bn to redevelop Fedora 9).Again, Garcia-Garcia and Alonso de Magdaleno from University of Oviedo (Spain) estimate that the value annually added to kernel was about €100M between 2005 and 2007 and €225M in 2008, it would cost also more than €1bn (about $1.4bn as of February 2010) to develop in the European Union.
As of 7 March 2011, using then-current LOC (lines of code) of a 2.6.x Linux kernel and wage numbers with David A. Wheeler's calculations it would cost approximately $3bn (about €2.2bn) to redevelop the Linux kernel as it keeps getting bigger.
Development model
This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (March 2011)
The current development model of the Linux kernel is such that Linus Torvalds makes the releases of new versions, also called the "vanilla" or "mainline" kernels, meaning that they contain the main, generic branch of development. This branch is officially released as a new version approximately every ten weeks, after Torvalds does an initial round of integrating major changes made by all other programmers, and several rounds of bug-fix pre-releases.
As of 2015, in the current development scheme, the main branch of development is not a traditional "stable" branch; instead, it incorporates all kinds of changes, including both the latest features, and security and bug fixes. For users who do not want to risk updating to new versions containing code that may not be well tested, a separate set of "stable" branches exist, one for each released version, which are meant for people who just want the security and bug fixes, but not a whole new version. These branches are maintained by the stable team (Greg Kroah-Hartman, Chris Wright, and others).
The development model for the 2.6 kernel series was significantly different compared to the 2.5 series. Before the 2.6, there was a stable branch (2.4) where only relatively minor and safe changes were merged, and an unstable branch (2.5), where bigger changes and cleanups were allowed. Both of these branches had been maintained by the same set of people, led by Torvalds. This meant that users would always have a well-tested 2.4 version with the latest security and bug fixes to use, though they would have to wait for the features which went into the 2.5 branch. The downside of this was that the "stable" kernel ended up so far behind that it no longer supported recent hardware and lacked needed features. In the late 2.5 kernel series, some maintainers elected to try backporting of their changes to the stable kernel series, what resulted in bugs being introduced into the 2.4 kernel series. The 2.5 branch was then eventually declared stable and renamed to 2.6. But instead of opening an unstable 2.7 branch, the kernel developers decided to continue putting major changes into the 2.6 branch, which would then be released at a pace faster than 2.4.x but slower than 2.5.x. This had the desirable effect of making new features more quickly available and getting more testing of the new code, which was added in smaller batches and easier to test.As a response to the lack of a stable kernel tree where people could coordinate the collection of bug fixes as such, in December 2005 Adrian Bunk announced that he would keep releasing 2.6.16.y kernels when the stable team moved on to 2.6.17.He also included some driver updates, making the maintenance of the 2.6.16 series very similar to the old rules for maintenance of a stable series such as 2.4.Since then, the "stable team" had been formed, and it would keep updating kernel versions with bug fixes. In October 2008 Adrian Bunk announced that he will maintain 2.6.27 for a few years as a replacement of 2.6.16.The stable team picked up on the idea and as of 2010 they continue to maintain that version and release bug fixes for it, in addition to others.
After the change of the development model with 2.6.x, developers continued to want what one might call an unstable kernel tree, one that changes as rapidly as new patches come in. Andrew Morton decided to repurpose his -mm tree from memory management to serve as the destination for all new and experimental code. In September 2007 Morton decided to stop maintaining this tree.In February 2008, Stephen Rothwell created the linux-next tree to serve as a place where patches aimed to be merged during the next development cycle are gathered.Several subsystem maintainers also adopted the suffix -next for trees containing code which is meant to be submitted for inclusion in the next release cycle.
As of January 2014 the currently in-development version of the Linux kernel is held in an unstable branch named linux-next.
Relation with Linux distributions
Most Linux users run a kernel supplied by their Linux distribution. Some distributions ship the "vanilla" or "stable" kernels. However, several Linux distribution vendors (such as Red Hat and Debian) maintain another set of Linux kernel branches which are integrated into their products. These are by and large updated at a slower pace compared to the "vanilla" branch, and they usually include all fixes from the relevant "stable" branch, but at the same time they can also add support for drivers or features which had not been released in the "vanilla" version the distribution vendor started basing their branch from.
Maintenance
While Linus Torvalds supervises code changes and releases to the latest kernel versions, he has delegated the maintenance of older versions to other programmers.Major releases as old as 2.0 (officially made obsolete with the kernel 2.2.0 release in January 1999) are maintained as needed, although at a very slow pace.
Releases before 2.6.0
Version Original release date Current version Maintainer Support model
0.01 17 September 1991 0.03 EOL
0.10 November 1991 0.12 EOL
0.95 8 March 1992 0.99.15 EOL
1.0 14 March 1994 1.0.9 EOL
1.1 6 April 1994 1.1.95 EOL
1.2 7 March 1995 1.2.13 EOL
1.3 12 June 1995 1.3.100 EOL
pre2.0 12 May 1996 pre2.0.14 EOL
2.0 9 June 1996 2.0.40 David Weinehall EOL (Officially made obsolete with the kernel 2.2.0 release)
2.2 26 January 1999 2.2.26 Marc-Christian Petersen (formerly Alan Cox) EOL (Unofficially obsolete with the 2.2.27-rc2)
2.4 4 January 2001 2.4.37.11 Willy Tarreau (formerly Marcelo Tosatti) EOL (Maintained from December 2008 to December 2011), last stable release of the 2.4 kernel series.
Legend:Old versionOlder version, still supportedLatest versionLatest preview version
2.6.x.y releases
Version Original release date Current version Maintainer Support model
2.6 17 December 2003 2.6.10 Linus Torvalds EOL (Maintained from December 2003 to December 2004)
2.6.11 2 March 2005 2.6.11.12 Greg Kroah-Hartman EOL (Maintained from March 2005 to June 2005)
2.6.12 18 June 2005 2.6.12.6 Greg Kroah-Hartman EOL (Maintained from June 2005 to August 2005)
2.6.13 28 August 2005 2.6.13.5 Greg Kroah-Hartman EOL (Maintained from August 2005 to December 2005)
2.6.14 27 October 2005 2.6.14.7 Greg Kroah-Hartman EOL (Maintained from October 2005 to January 2006)
2.6.15 2 January 2006 2.6.15.7 Greg Kroah-Hartman EOL (Maintained from January 2006 to May 2006)
2.6.16 20 March 2006 2.6.16.62 Adrian Bunk (formerly Greg Kroah-Hartman) EOL (First long-term stable release from March 2006 to July 2008)
2.6.17 17 June 2006 2.6.17.14 Greg Kroah-Hartman EOL (Maintained from September 2006 to October 2006)
2.6.18 20 September 2006 2.6.18.8 Greg Kroah-Hartman EOL (Maintained from September 2006 to February 2007)
2.6.19 26 November 2006 2.6.19.7 Greg Kroah-Hartman EOL (Maintained from November 2006 to March 2007)
2.6.20 4 February 2007 2.6.20.21 Greg Kroah-Hartman EOL (Maintained from February 2007 to October 2007)
2.6.21 25 April 2007 2.6.21.7 Greg Kroah-Hartman EOL (Maintained from April 2007 to August 2007)
2.6.22 8 July 2007 2.6.22.19 Greg Kroah-Hartman EOL (Maintained from July 2007 to February 2008)
2.6.23 9 October 2007 2.6.23.17 Greg Kroah-Hartman EOL (Maintained from October 2007 to February 2008)
2.6.24 24 January 2008 2.6.24.7 Greg Kroah-Hartman EOL (Maintained from January 2008 to May 2008)
2.6.25 16 April 2008 2.6.25.20 Greg Kroah-Hartman EOL (Maintained from April 2008 to November 2008)
2.6.26 13 July 2008 2.6.26.8 Greg Kroah-Hartman EOL (Maintained from July 2008 to November 2008)
2.6.27 9 October 2008 2.6.27.62 Willy Tarreau (formerly Adrian Bunk,Greg Kroah-Hartman) EOL (Second long-term stable release from October 2008 to March 2012)
2.6.28 24 December 2008 2.6.28.10 Greg Kroah-Hartman EOL (Maintained from December 2008 to May 2009)
2.6.29 23 March 2009 2.6.29.6 Greg Kroah-Hartman EOL (Maintained from March 2009 to July 2009)
2.6.30 9 June 2009 2.6.30.9 Greg Kroah-Hartman EOL (Maintained from June 2009 to October 2009)
2.6.31 9 September 2009 2.6.31.14 Greg Kroah-Hartman EOL (Maintained from September 2009 to July 2010)
2.6.32 2 December 2009 2.6.32.65 Willy Tarreau (formerly Greg Kroah-Hartman)Third long-term stable release from December 2009 to mid-2015,used in Debian 6 Squeeze.Canonical will also provide support until April 2015.
2.6.33 24 February 2010 2.6.33.20 Greg Kroah-Hartman EOL (Fourth long-term stable release from March 2011 to November 2011). Base for Real-Time-Tree, replaced by 3.0.x
2.6.34 16 May 2010 2.6.34.15 Paul Gortmaker EOL (Fifth long-term stable release from January 2011 to February 2014)
2.6.35 1 August 2010 2.6.35.14 Andi Kleen EOL (Sixth long-term stable release from December 2010 to March 2012)
2.6.36 20 October 2010 2.6.36.4 Greg Kroah-Hartman EOL (Maintained from October 2010 to February 2011)
2.6.37 4 January 2011 2.6.37.6 Greg Kroah-Hartman EOL (Maintained from January 2011 to March 2011)
2.6.38 14 March 2011 2.6.38.8 Greg Kroah-Hartman EOL (Maintained from March 2011 to June 2011)
2.6.39 18 May 2011 2.6.39.4 Greg Kroah-Hartman EOL (Maintained from May 2011 to August 2011), last stable release of the 2.6 kernel series.
Legend:Old versionOlder version, still supportedLatest versionLatest preview version
3.x.y releases
Version Original release date Current version Maintainer Support model
3.0 21 July 2011 3.0.101 Greg Kroah-HartmanEOL (Seventh long-term stable release from July 2011 to October 2013 (Base for Real-Time-Tree))
3.1 24 October 2011 3.1.10 Greg Kroah-Hartman EOL (Maintained from October 2011 to January 2012)
3.2 4 January 2012 3.2.68 Ben Hutchings Eighth long-term stable release from March 2012 to 2016, used in Ubuntu 12.04 LTS, Debian 7 Wheezy and Slackware 14.0.Canonical will provide extended support until April 2017.
3.3 18 March 2012 3.3.8 Greg Kroah-Hartman EOL (Maintained from March 2012 to June 2012)
3.4 20 May 2012 3.4.107 Li Zefan (formerly Greg Kroah-Hartman) Ninth long-term stable release from May 2012 to September 2016
3.5 21 July 2012 3.5.7 Greg Kroah-Hartman EOL (Maintained by Kroah-Hartman until the release of 3.6.1, from July 2012 to October 2012).Canonical provides extended support until April 2014.
3.6 30 September 2012 3.6.11 Greg Kroah-Hartman EOL (Maintained from October 2012 to December 2012)
3.7 10 December 2012 3.7.10 Greg Kroah-Hartman EOL (Maintained from December 2012 to March 2013)
3.8 18 February 2013 3.8.13 Greg Kroah-Hartman EOL (Maintained from February 2013 to May 2013).Canonical provides extended support until August 2014.
3.9 28 April 2013 3.9.11 Greg Kroah-Hartman EOL (Maintained from April 2013 to July 2013)
3.10 30 June 2013 3.10.75 Greg Kroah-Hartman Tenth long-term stable release from August 2013 to September 2015.
3.11 2 September 2013 3.11.10 Greg Kroah-Hartman EOL (Maintained from September 2013 to November 2013).Canonical provides extended support until August 2014.The codename chosen for version 3.11 is Linux for Workgroups.
3.12 3 November 2013 3.12.40 Jirí Slabý (formerly Greg Kroah-Hartman) Eleventh long-term stable release from November 2013 to 2016
3.13 19 January 2014 3.13.11 Greg Kroah-Hartman EOL (Maintained from January 2014 to April 2014).Canonical provides extended support until April 2016.
3.14 30 March 2014 3.14.39 Greg Kroah-HartmanTwelfth long-term stable release from March 2014 to August 2016
3.15 8 June 2014 3.15.10 Greg Kroah-Hartman EOL (Maintained from June 2014 to August 2014)
3.16 3 August 2014 3.16.7 Greg Kroah-Hartman EOL (Maintained from August 2014 to October 2014)Canonical provides extended support until April 2016.
3.17 5 October 2014 3.17.8 Greg Kroah-Hartman EOL (Maintained from October 2014 to January 2015)
3.18 7 December 2014 3.18.12 Sasha Levin
(formerly Greg Kroah-Hartman)
Thirteenth long-term stable release from December 2014 to January 2017
3.19 8 February 2015 3.19.5 Greg Kroah-Hartman Last stable release of the 3 kernel series.
Legend:Old versionOlder version, still supportedLatest versionLatest preview version
4.x.y releases
Version Original release date Current version Maintainer Support model
4.0 12 April 2015 4.0 Linus Torvalds Latest Stable
Legend:Old versionOlder version, still supportedLatest versionLatest preview version
Revision control
The Linux kernel source code used to be maintained without the help of an automated source code management system, mostly because of Linus Torvalds' dislike of centralized SCM systems.
In 2002, Linux kernel development switched to BitKeeper, an SCM system which satisfied Linus Torvalds' technical requirements. BitKeeper was made available to Linus and several others free of charge, but was not free software, which was a source of controversy. The system did provide some interoperability with free SCM systems such as CVS and Subversion.
In April 2005, however, efforts to reverse-engineer the BitKeeper system by Andrew Tridgell led BitMover, the company which maintained BitKeeper, to stop supporting the Linux development community. In response, Linus Torvalds and others wrote a new source code control system for the purpose, called Git. The new system was written within weeks, and in two months the first official kernel release was made using Git.Git soon developed into a separate project in its own right and gained wide adoption in the free software community.
Version numbering
The Linux kernel has had three different numbering schemes.
The first scheme was used in the run-up to "1.0". The first version of the kernel was 0.01. This was followed by 0.02, 0.03, 0.10, 0.11, 0.12 (the first GPL version), 0.95, 0.96, 0.97, 0.98, 0.99 and then 1.0.From 0.95 on there were many patch releases between versions.
After the 1.0 release and prior to version 2.6, the number was composed as "a.b.c", where the number "a" denoted the kernel version, the number "b" denoted the major revision of the kernel, and the number "c" indicated the minor revision of the kernel. The kernel version was changed only when major changes in the code and the concept of the kernel occurred, twice in the history of the kernel: in 1994 (version 1.0) and in 1996 (version 2.0). Version 3.0 was released in 2011, but it was not a major change in kernel concept. The major revision was assigned according to the traditional even-odd system version numbering system. The minor revision had been changed whenever security patches, bug fixes, new features or drivers were implemented in the kernel.
In 2004, after version 2.6.0 was released, the kernel developers held several discussions regarding the release and version scheme and ultimately Linus Torvalds and others decided that a much shorter "time-based" release cycle would be beneficial. For about seven years, the first two numbers remained "2.6", and the third number was incremented with each new release, which rolled out after two to three months. A fourth number was sometimes added to account for bug and security fixes (only) to the kernel version. The even-odd system of alternation between stable and unstable was gone. Instead, development pre-releases are titled release candidates, which is indicated by appending the suffix '-rc' to the kernel version, followed by an ordinal number.
The first use of the fourth number occurred when a grave error, which required immediate fixing, was encountered in 2.6.8's NFS code. However, there were not enough other changes to legitimize the release of a new minor revision (which would have been 2.6.9). So, 2.6.8.1 was released, with the only change being the fix of that error. With 2.6.11, this was adopted as the new official versioning policy. Later it became customary to continuously back-port major bug-fixes and security patches to released kernels and indicate that by updating the fourth number.
On 29 May 2011, Linus Torvalds announced that the kernel version would be bumped to 3.0 for the release following 2.6.39, due to the minor version number getting too large and to commemorate the 20th anniversary of Linux. It continued the time-based release practice introduced with 2.6.0, but using the second number; for example, 3.1 would follow 3.0 after a few months. An additional number (now the third number) would be added on when necessary to designate security and bug fixes, as for example with 3.0.18; the Linux community refers to this as "3.x.y.z" versioning. The major version number was also later raised to 4, for the release following version 3.19.
In addition to Linus's "-rc" development releases, sometimes the version will have a suffix such as "tip", indicating another development branch, usually (but not always) the initials of a person who made it. For example, "ck" stands for Con Kolivas, "ac" stands for Alan Cox, etc. Sometimes, the letters are related to the primary development area of the branch the kernel is built from, for example, "wl" indicates a wireless networking test build. Also, distributors may have their own suffixes with different numbering systems and for back-ports to their "enterprise" (i.e. stable but older) distribution versions.
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Android software development is the process by which new applications are created for the Android operating system. Applications are usually developed in Java programming language using the Android Software Development Kit (SDK), but other development environments are also available.
As of July 2013, more than one million applications have been developed for Android,with over 25 billion downloads.A June 2011 research indicated that over 67% of mobile developers used the platform, at the time of publication.In Q2 2012, around 105 million units of Android smartphones were shipped which acquires a total share of 68% in overall smartphones sale till Q2 2012.
1.1 Android SDK
1.1.1 Android Debug Bridge
1.1.2 Fastboot
1.2 Android NDK
1.3 Android Open Accessory Development Kit
2 Third-party development tools
2.1 Android APIMiner
2.2 AndroWish
2.3 App Inventor for Android
2.4 Basic4android
2.5 Corona SDK
2.6 Delphi
2.7 HyperNext Android Creator
2.8 Kivy
2.9 Lazarus
2.10 Processing
2.11 Qt for Android
2.12 RFO BASIC!
2.13 RubyMotion
2.14 Saphir
2.15 SDL
2.16 The Simple project
2.17 WinDev Mobile
2.18 Xamarin
2.19 X11 Basic
3 Android Developer Challenge
4 Community-based firmware
5 Java standards
6 History
Android software development kit (Android SDK)
Developer(s) Google
Initial release October 2009; 5 years ago
Stable release 24.0.2 / December 2014; 4 months ago
Written in Java
Operating system Cross-platform
Available in English
Type IDE, SDK
Website :-developer.android.com/tools/sdk/eclipse-adt.html, developer.android.com/sdk/index.html
The Android software development kit (SDK) includes a comprehensive set of development tools.These include a debugger, libraries, a handset emulator based on QEMU, documentation, sample code, and tutorials. Currently supported development platforms include computers running Linux (any modern desktop Linux distribution), Mac OS X 10.5.8 or later, and Windows XP or later. As of March 2015, the SDK is not available on Android itself, but the software development is possible by using specialized Android applications.
Until around the end of 2014, the officially supported integrated development environment (IDE) was Eclipse using the Android Development Tools (ADT) Plugin, though IntelliJ IDEA IDE (all editions) fully supports Android development out of the box,and NetBeans IDE also supports Android development via a plugin.As of 2015, Android Studio,made by Google and powered by IntelliJ, is the official IDE; however, developers are free to use others. Additionally, developers may use any text editor to edit Java and XML files, then use command line tools (Java Development Kit and Apache Ant are required) to create, build and debug Android applications as well as control attached Android devices (e.g., triggering a reboot, installing software package(s) remotely).
Enhancements to Android's SDK go hand in hand with the overall Android platform development. The SDK also supports older versions of the Android platform in case developers wish to target their applications at older devices. Development tools are downloadable components, so after one has downloaded the latest version and platform, older platforms and tools can also be downloaded for compatibility testing.
Android applications are packaged in .apk format and stored under /data/app folder on the Android OS (the folder is accessible only to the root user for security reasons). APK package contains .dex files (compiled byte code files called Dalvik executables), resource files, etc.
The format for issuing commands through the ADB is typically:
adb [-d|-e|-s <serialNumber>] <command>
In a security issue reported in March 2011, ADB was targeted as a vector to attempt to install a rootkit on connected phones using a "resource exhaustion attack".
Fastboot is a diagnostic protocol included with the SDK package used primarily to modify the flash filesystem via a USB connection from host computer. It requires that the device be started in a boot loader or Second Program Loader mode in which only the most basic hardware initialization is performed. After enabling the protocol on the device itself, it will accept a specific set of commands sent to it via USB using a command line. Some of the most commonly used fastboot commands include:
flash – rewrites a partition with a binary image stored on the host computer
erase – erases a specific partition
reboot – reboots the device into either the main operating system, the system recovery partition or back into its bootloader
devices – displays a list of all devices (with the serial number) connected to the host computer
format – formats a specific partition; the file system of the partition must be recognized by the device
Android NDK
Android Native Development Kit (Android NDK)
Developer(s) Google
Initial release June 2009; 5 years ago
Stable release 10d / December 2014; 4 months ago
Written in C and C++
Operating system Cross-platform
Available in English
Type IDE, SDK
Website developer.android.com/tools/sdk/ndk/index.html
Libraries written in C, C++ and other languages can be compiled to ARM, MIPS or x86 native code and installed using the Android Native Development Kit (NDK). Native classes can be called from Java code running under the Dalvik VM using the System.loadLibrary call, which is part of the standard Android Java classes.
Complete applications can be compiled and installed using traditional development tools.However, according to the Android documentation, NDK should not be used solely for developing applications only because the developer prefers to program in C/C++, as using NDK increases complexity while most applications would not benefit from using it.
The ADB debugger gives a root shell under the Android Emulator which allows ARM, MIPS or x86 native code to be uploaded and executed. Native code can be compiled using GCC or the Intel C++ Compiler on a standard PC.Running native code is complicated by Android's use of a non-standard C library (libc, known as Bionic). The graphics library that Android uses to arbitrate and control access to this device is called the Skia Graphics Library (SGL), and it has been released under an open source licence.Skia has backends for both Win32 and Unix, allowing the development of cross-platform applications, and it is the graphics engine underlying the Google Chrome web browser.
Unlike Java application development based on an IDE such as Eclipse, the NDK is based on command-line tools and requires invoking them manually to build, deploy and debug the apps. Several third-party tools allow integrating the NDK into Eclipse and Visual Studio.
Android APIMiner is a platform that automatically instruments the Javadoc documentation of the Android API with examples of usage, extracted from real open-source Android applications.To improve the quality of the extracted examples, APIMiner relies on an intra-procedural static slicing algorithm.
AndroWish
AndroWish is an on-device Tcl/Tk interpreter which provides multi-windows GUI and give access to Bluetooth, USB, network sockets, text-to-speech, speech recognition, sensor, location (GPS or network information), activity manager, SQLite and sound. The GUI layer relies on SDL2. AndroWish is provided with 337 Tcl packages.
In the second half of 2011, Google released the source code, terminated its Web service, and provided funding for the creation of The MIT Center for Mobile Learning, led by the App Inventor creator Hal Abelson and fellow MIT professors Eric Klopfer and Mitchel Resnick.Latest version created as the result of Google–MIT collaboration was released in February 2012, while the first version created solely by MIT was launched in March 2012 and upgraded to App Inventor 2 in December 2013.As of 2014, App inventor is now maintained by MIT.
Corona lets developers use integrated Lua, layered on top of C++/OpenGL, to build graphic applications. The SDK does not charge per-app royalty or impose any branding requirement, and has a subscription-based purchase model.
Similar to Microsoft Visual Basic 6, Simple programs are form definitions (which contain components) and code (which contains the program logic). The interaction between the components and the program logic happens through events triggered by the components. The program logic consists of event handlers which contain code reacting to the events.
The Simple project is not very active,the last source code update being in August 2009.
ADC II was announced on May 27, 2009.The first round of the ADC II closed on October 6, 2009.The first-round winners of ADC II comprising the top 200 applications were announced on November 5, 2009. Voting for the second round also opened on the same day and ended on November 25. Google announced the top winners of ADC II on November 30, with SweetDreams, What the Doodle!? and WaveSecure being nominated the overall winners of the challenge.
Those firmware packages are updated frequently, incorporate elements of Android functionality that haven't yet been officially released within a carrier-sanctioned firmware, and tend to have fewer limitations. CyanogenMod and OMFGB are examples of such firmware.
On September 24, 2009, Google issued a cease and desist letter to the modder Cyanogen, citing issues with the re-distribution of Google's closed-source applications within the custom firmware. Even though most of Android OS is open source, phones come packaged with closed-source Google applications for functionality such as the Android Market and GPS navigation. Google has asserted that these applications can only be provided through approved distribution channels by licensed distributors. Cyanogen has complied with Google's wishes and is continuing to distribute this mod without the proprietary software. It has provided a method to back up licensed Google applications during the mod's install process and restore them when the process is complete.
Obstacles to development include the fact that Android does not use established Java standards, that is, Java SE and ME. This prevents compatibility between Java applications written for those platforms and those written for the Android platform. Android only reuses the Java language syntax and semantics, but it does not provide the full class libraries and APIs bundled with Java SE or ME.However, there are multiple tools in the market from companies such as Myriad Group and UpOnTek that provide Java ME to Android conversion services.
The "Sooner" prototype phone,prior to "Dream"
Android was created by the Open Handset Alliance, which is led by Google. The early feedback on developing applications for the Android platform was mixed.Issues cited include bugs, lack of documentation, inadequate QA infrastructure, and no public issue-tracking system. (Google announced an issue tracker on January 18, 2008.)In December 2007, MergeLab mobile startup founder Adam MacBeth stated, "Functionality is not there, is poorly documented or just doesn't work... It's clearly not ready for prime time." Despite this, Android-targeted applications began to appear the week after the platform was announced. The first publicly available application was the Snake game.The Android Dev Phone is a SIM-unlocked and hardware-unlocked device that is designed for advanced developers. While developers can use regular consumer devices purchased at retail to test and use their applications, some developers may choose not to use a retail device, preferring an unlocked or no-contract device.
A preview release of the Android SDK was released on November 12, 2007. On July 15, 2008, the Android Developer Challenge Team accidentally sent an email to all entrants in the Android Developer Challenge announcing that a new release of the SDK was available in a "private" download area. The email was intended for winners of the first round of the Android Developer Challenge. The revelation that Google was supplying new SDK releases to some developers and not others (and keeping this arrangement private) led to widely reported frustration within the Android developer community at the time.
On August 18, 2008, the Android 0.9 SDK beta was released. This release provided an updated and extended API, improved development tools and an updated design for the home screen. Detailed instructions for upgrading are available to those already working with an earlier release.On September 23, 2008, the Android 1.0 SDK (Release 1) was released.According to the release notes, it included "mainly bug fixes, although some smaller features were added." It also included several API changes from the 0.9 version. Multiple versions have been released since it was developed .
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Android software development is the process by which new applications are created for the Android operating system. Applications are usually developed in Java programming language using the Android Software Development Kit (SDK), but other development environments are also available.
As of July 2013, more than one million applications have been developed for Android,with over 25 billion downloads.A June 2011 research indicated that over 67% of mobile developers used the platform, at the time of publication.In Q2 2012, around 105 million units of Android smartphones were shipped which acquires a total share of 68% in overall smartphones sale till Q2 2012.
1.1 Android SDK
1.1.1 Android Debug Bridge
1.1.2 Fastboot
1.2 Android NDK
1.3 Android Open Accessory Development Kit
2 Third-party development tools
2.1 Android APIMiner
2.2 AndroWish
2.3 App Inventor for Android
2.4 Basic4android
2.5 Corona SDK
2.6 Delphi
2.7 HyperNext Android Creator
2.8 Kivy
2.9 Lazarus
2.10 Processing
2.11 Qt for Android
2.12 RFO BASIC!
2.13 RubyMotion
2.14 Saphir
2.15 SDL
2.16 The Simple project
2.17 WinDev Mobile
2.18 Xamarin
2.19 X11 Basic
3 Android Developer Challenge
4 Community-based firmware
5 Java standards
6 History
Android software development kit (Android SDK)
Developer(s) Google
Initial release October 2009; 5 years ago
Stable release 24.0.2 / December 2014; 4 months ago
Written in Java
Operating system Cross-platform
Available in English
Type IDE, SDK
Website :-developer.android.com/tools/sdk/eclipse-adt.html, developer.android.com/sdk/index.html
The Android software development kit (SDK) includes a comprehensive set of development tools.These include a debugger, libraries, a handset emulator based on QEMU, documentation, sample code, and tutorials. Currently supported development platforms include computers running Linux (any modern desktop Linux distribution), Mac OS X 10.5.8 or later, and Windows XP or later. As of March 2015, the SDK is not available on Android itself, but the software development is possible by using specialized Android applications.
Until around the end of 2014, the officially supported integrated development environment (IDE) was Eclipse using the Android Development Tools (ADT) Plugin, though IntelliJ IDEA IDE (all editions) fully supports Android development out of the box,and NetBeans IDE also supports Android development via a plugin.As of 2015, Android Studio,made by Google and powered by IntelliJ, is the official IDE; however, developers are free to use others. Additionally, developers may use any text editor to edit Java and XML files, then use command line tools (Java Development Kit and Apache Ant are required) to create, build and debug Android applications as well as control attached Android devices (e.g., triggering a reboot, installing software package(s) remotely).
Enhancements to Android's SDK go hand in hand with the overall Android platform development. The SDK also supports older versions of the Android platform in case developers wish to target their applications at older devices. Development tools are downloadable components, so after one has downloaded the latest version and platform, older platforms and tools can also be downloaded for compatibility testing.
Android applications are packaged in .apk format and stored under /data/app folder on the Android OS (the folder is accessible only to the root user for security reasons). APK package contains .dex files (compiled byte code files called Dalvik executables), resource files, etc.
The format for issuing commands through the ADB is typically:
adb [-d|-e|-s <serialNumber>] <command>
In a security issue reported in March 2011, ADB was targeted as a vector to attempt to install a rootkit on connected phones using a "resource exhaustion attack".
Fastboot is a diagnostic protocol included with the SDK package used primarily to modify the flash filesystem via a USB connection from host computer. It requires that the device be started in a boot loader or Second Program Loader mode in which only the most basic hardware initialization is performed. After enabling the protocol on the device itself, it will accept a specific set of commands sent to it via USB using a command line. Some of the most commonly used fastboot commands include:
flash – rewrites a partition with a binary image stored on the host computer
erase – erases a specific partition
reboot – reboots the device into either the main operating system, the system recovery partition or back into its bootloader
devices – displays a list of all devices (with the serial number) connected to the host computer
format – formats a specific partition; the file system of the partition must be recognized by the device
Android NDK
Android Native Development Kit (Android NDK)
Developer(s) Google
Initial release June 2009; 5 years ago
Stable release 10d / December 2014; 4 months ago
Written in C and C++
Operating system Cross-platform
Available in English
Type IDE, SDK
Website developer.android.com/tools/sdk/ndk/index.html
Libraries written in C, C++ and other languages can be compiled to ARM, MIPS or x86 native code and installed using the Android Native Development Kit (NDK). Native classes can be called from Java code running under the Dalvik VM using the System.loadLibrary call, which is part of the standard Android Java classes.
Complete applications can be compiled and installed using traditional development tools.However, according to the Android documentation, NDK should not be used solely for developing applications only because the developer prefers to program in C/C++, as using NDK increases complexity while most applications would not benefit from using it.
The ADB debugger gives a root shell under the Android Emulator which allows ARM, MIPS or x86 native code to be uploaded and executed. Native code can be compiled using GCC or the Intel C++ Compiler on a standard PC.Running native code is complicated by Android's use of a non-standard C library (libc, known as Bionic). The graphics library that Android uses to arbitrate and control access to this device is called the Skia Graphics Library (SGL), and it has been released under an open source licence.Skia has backends for both Win32 and Unix, allowing the development of cross-platform applications, and it is the graphics engine underlying the Google Chrome web browser.
Unlike Java application development based on an IDE such as Eclipse, the NDK is based on command-line tools and requires invoking them manually to build, deploy and debug the apps. Several third-party tools allow integrating the NDK into Eclipse and Visual Studio.
Android APIMiner is a platform that automatically instruments the Javadoc documentation of the Android API with examples of usage, extracted from real open-source Android applications.To improve the quality of the extracted examples, APIMiner relies on an intra-procedural static slicing algorithm.
AndroWish
AndroWish is an on-device Tcl/Tk interpreter which provides multi-windows GUI and give access to Bluetooth, USB, network sockets, text-to-speech, speech recognition, sensor, location (GPS or network information), activity manager, SQLite and sound. The GUI layer relies on SDL2. AndroWish is provided with 337 Tcl packages.
In the second half of 2011, Google released the source code, terminated its Web service, and provided funding for the creation of The MIT Center for Mobile Learning, led by the App Inventor creator Hal Abelson and fellow MIT professors Eric Klopfer and Mitchel Resnick.Latest version created as the result of Google–MIT collaboration was released in February 2012, while the first version created solely by MIT was launched in March 2012 and upgraded to App Inventor 2 in December 2013.As of 2014, App inventor is now maintained by MIT.
Corona lets developers use integrated Lua, layered on top of C++/OpenGL, to build graphic applications. The SDK does not charge per-app royalty or impose any branding requirement, and has a subscription-based purchase model.
Similar to Microsoft Visual Basic 6, Simple programs are form definitions (which contain components) and code (which contains the program logic). The interaction between the components and the program logic happens through events triggered by the components. The program logic consists of event handlers which contain code reacting to the events.
The Simple project is not very active,the last source code update being in August 2009.
ADC II was announced on May 27, 2009.The first round of the ADC II closed on October 6, 2009.The first-round winners of ADC II comprising the top 200 applications were announced on November 5, 2009. Voting for the second round also opened on the same day and ended on November 25. Google announced the top winners of ADC II on November 30, with SweetDreams, What the Doodle!? and WaveSecure being nominated the overall winners of the challenge.
Those firmware packages are updated frequently, incorporate elements of Android functionality that haven't yet been officially released within a carrier-sanctioned firmware, and tend to have fewer limitations. CyanogenMod and OMFGB are examples of such firmware.
On September 24, 2009, Google issued a cease and desist letter to the modder Cyanogen, citing issues with the re-distribution of Google's closed-source applications within the custom firmware. Even though most of Android OS is open source, phones come packaged with closed-source Google applications for functionality such as the Android Market and GPS navigation. Google has asserted that these applications can only be provided through approved distribution channels by licensed distributors. Cyanogen has complied with Google's wishes and is continuing to distribute this mod without the proprietary software. It has provided a method to back up licensed Google applications during the mod's install process and restore them when the process is complete.
Obstacles to development include the fact that Android does not use established Java standards, that is, Java SE and ME. This prevents compatibility between Java applications written for those platforms and those written for the Android platform. Android only reuses the Java language syntax and semantics, but it does not provide the full class libraries and APIs bundled with Java SE or ME.However, there are multiple tools in the market from companies such as Myriad Group and UpOnTek that provide Java ME to Android conversion services.
The "Sooner" prototype phone,prior to "Dream"
Android was created by the Open Handset Alliance, which is led by Google. The early feedback on developing applications for the Android platform was mixed.Issues cited include bugs, lack of documentation, inadequate QA infrastructure, and no public issue-tracking system. (Google announced an issue tracker on January 18, 2008.)In December 2007, MergeLab mobile startup founder Adam MacBeth stated, "Functionality is not there, is poorly documented or just doesn't work... It's clearly not ready for prime time." Despite this, Android-targeted applications began to appear the week after the platform was announced. The first publicly available application was the Snake game.The Android Dev Phone is a SIM-unlocked and hardware-unlocked device that is designed for advanced developers. While developers can use regular consumer devices purchased at retail to test and use their applications, some developers may choose not to use a retail device, preferring an unlocked or no-contract device.
A preview release of the Android SDK was released on November 12, 2007. On July 15, 2008, the Android Developer Challenge Team accidentally sent an email to all entrants in the Android Developer Challenge announcing that a new release of the SDK was available in a "private" download area. The email was intended for winners of the first round of the Android Developer Challenge. The revelation that Google was supplying new SDK releases to some developers and not others (and keeping this arrangement private) led to widely reported frustration within the Android developer community at the time.
On August 18, 2008, the Android 0.9 SDK beta was released. This release provided an updated and extended API, improved development tools and an updated design for the home screen. Detailed instructions for upgrading are available to those already working with an earlier release.On September 23, 2008, the Android 1.0 SDK (Release 1) was released.According to the release notes, it included "mainly bug fixes, although some smaller features were added." It also included several API changes from the 0.9 version. Multiple versions have been released since it was developed .
=======================================================================
SOFTWARE DEVELOPMENT (ANDROID)
Android software development is the process by which new applications are created for the Android operating system. Applications are usually developed in Java programming language using the Android Software Development Kit (SDK), but other development environments are also available.
As of July 2013, more than one million applications have been developed for Android,with over 25 billion downloads.A June 2011 research indicated that over 67% of mobile developers used the platform, at the time of publication.In Q2 2012, around 105 million units of Android smartphones were shipped which acquires a total share of 68% in overall smartphones sale till Q2 2012.
Contents
1 Official development tools1.1 Android SDK
1.1.1 Android Debug Bridge
1.1.2 Fastboot
1.2 Android NDK
1.3 Android Open Accessory Development Kit
2 Third-party development tools
2.1 Android APIMiner
2.2 AndroWish
2.3 App Inventor for Android
2.4 Basic4android
2.5 Corona SDK
2.6 Delphi
2.7 HyperNext Android Creator
2.8 Kivy
2.9 Lazarus
2.10 Processing
2.11 Qt for Android
2.12 RFO BASIC!
2.13 RubyMotion
2.14 Saphir
2.15 SDL
2.16 The Simple project
2.17 WinDev Mobile
2.18 Xamarin
2.19 X11 Basic
3 Android Developer Challenge
4 Community-based firmware
5 Java standards
6 History
Official development tools
Android SDKAndroid software development kit (Android SDK)
Developer(s) Google
Initial release October 2009; 5 years ago
Stable release 24.0.2 / December 2014; 4 months ago
Written in Java
Operating system Cross-platform
Available in English
Type IDE, SDK
Website :-developer.android.com/tools/sdk/eclipse-adt.html, developer.android.com/sdk/index.html
The Android software development kit (SDK) includes a comprehensive set of development tools.These include a debugger, libraries, a handset emulator based on QEMU, documentation, sample code, and tutorials. Currently supported development platforms include computers running Linux (any modern desktop Linux distribution), Mac OS X 10.5.8 or later, and Windows XP or later. As of March 2015, the SDK is not available on Android itself, but the software development is possible by using specialized Android applications.
Until around the end of 2014, the officially supported integrated development environment (IDE) was Eclipse using the Android Development Tools (ADT) Plugin, though IntelliJ IDEA IDE (all editions) fully supports Android development out of the box,and NetBeans IDE also supports Android development via a plugin.As of 2015, Android Studio,made by Google and powered by IntelliJ, is the official IDE; however, developers are free to use others. Additionally, developers may use any text editor to edit Java and XML files, then use command line tools (Java Development Kit and Apache Ant are required) to create, build and debug Android applications as well as control attached Android devices (e.g., triggering a reboot, installing software package(s) remotely).
Enhancements to Android's SDK go hand in hand with the overall Android platform development. The SDK also supports older versions of the Android platform in case developers wish to target their applications at older devices. Development tools are downloadable components, so after one has downloaded the latest version and platform, older platforms and tools can also be downloaded for compatibility testing.
Android applications are packaged in .apk format and stored under /data/app folder on the Android OS (the folder is accessible only to the root user for security reasons). APK package contains .dex files (compiled byte code files called Dalvik executables), resource files, etc.
Android Debug Bridge
The Android Debug Bridge (ADB) is a toolkit included in the Android SDK package. It consists of both client and server-side programs that communicate with one another. The ADB is typically accessed through the command-line interface,although numerous graphical user interfaces exist to control ADB.The format for issuing commands through the ADB is typically:
adb [-d|-e|-s <serialNumber>] <command>
In a security issue reported in March 2011, ADB was targeted as a vector to attempt to install a rootkit on connected phones using a "resource exhaustion attack".
Fastboot
"Fastboot" redirects here. For the PC fast booting ability, see Instant-on.Fastboot is a diagnostic protocol included with the SDK package used primarily to modify the flash filesystem via a USB connection from host computer. It requires that the device be started in a boot loader or Second Program Loader mode in which only the most basic hardware initialization is performed. After enabling the protocol on the device itself, it will accept a specific set of commands sent to it via USB using a command line. Some of the most commonly used fastboot commands include:
flash – rewrites a partition with a binary image stored on the host computer
erase – erases a specific partition
reboot – reboots the device into either the main operating system, the system recovery partition or back into its bootloader
devices – displays a list of all devices (with the serial number) connected to the host computer
format – formats a specific partition; the file system of the partition must be recognized by the device
Android NDK
Android Native Development Kit (Android NDK)
Developer(s) Google
Initial release June 2009; 5 years ago
Stable release 10d / December 2014; 4 months ago
Written in C and C++
Operating system Cross-platform
Available in English
Type IDE, SDK
Website developer.android.com/tools/sdk/ndk/index.html
Libraries written in C, C++ and other languages can be compiled to ARM, MIPS or x86 native code and installed using the Android Native Development Kit (NDK). Native classes can be called from Java code running under the Dalvik VM using the System.loadLibrary call, which is part of the standard Android Java classes.
Complete applications can be compiled and installed using traditional development tools.However, according to the Android documentation, NDK should not be used solely for developing applications only because the developer prefers to program in C/C++, as using NDK increases complexity while most applications would not benefit from using it.
The ADB debugger gives a root shell under the Android Emulator which allows ARM, MIPS or x86 native code to be uploaded and executed. Native code can be compiled using GCC or the Intel C++ Compiler on a standard PC.Running native code is complicated by Android's use of a non-standard C library (libc, known as Bionic). The graphics library that Android uses to arbitrate and control access to this device is called the Skia Graphics Library (SGL), and it has been released under an open source licence.Skia has backends for both Win32 and Unix, allowing the development of cross-platform applications, and it is the graphics engine underlying the Google Chrome web browser.
Unlike Java application development based on an IDE such as Eclipse, the NDK is based on command-line tools and requires invoking them manually to build, deploy and debug the apps. Several third-party tools allow integrating the NDK into Eclipse and Visual Studio.
Android Open Accessory Development Kit
The Android 3.1 platform (also backported to Android 2.3.4) introduces Android Open Accessory support, which allows external USB hardware (an Android USB accessory) to interact with an Android-powered device in a special "accessory" mode. When an Android-powered device is in accessory mode, the connected accessory acts as the USB host (powers the bus and enumerates devices) and the Android-powered device acts as the USB device. Android USB accessories are specifically designed to attach to Android-powered devices and adhere to a simple protocol (Android accessory protocol) that allows them to detect Android-powered devices that support accessory mode.Third-party development tools
Android APIMinerAndroid APIMiner is a platform that automatically instruments the Javadoc documentation of the Android API with examples of usage, extracted from real open-source Android applications.To improve the quality of the extracted examples, APIMiner relies on an intra-procedural static slicing algorithm.
AndroWish
AndroWish is an on-device Tcl/Tk interpreter which provides multi-windows GUI and give access to Bluetooth, USB, network sockets, text-to-speech, speech recognition, sensor, location (GPS or network information), activity manager, SQLite and sound. The GUI layer relies on SDL2. AndroWish is provided with 337 Tcl packages.
App Inventor for Android
On July 12, 2010, Google announced the availability of App Inventor for Android, a Web-based visual development environment for novice programmers, based on MIT's Open Blocks Java library and providing access to Android devices' GPS, accelerometer and orientation data, phone functions, text messaging, speech-to-text conversion, contact data, persistent storage, and Web services, initially including Amazon and Twitter."We could only have done this because Android’s architecture is so open," said the project director, MIT's Hal Abelson.Under development for over a year,the block-editing tool has been taught to non-majors in computer science at Harvard, MIT, Wellesley, Trinity College (Hartford,) and the University of San Francisco, where Professor David Wolber developed an introductory computer science course and tutorial book for non-computer science students based on App Inventor for Android.In the second half of 2011, Google released the source code, terminated its Web service, and provided funding for the creation of The MIT Center for Mobile Learning, led by the App Inventor creator Hal Abelson and fellow MIT professors Eric Klopfer and Mitchel Resnick.Latest version created as the result of Google–MIT collaboration was released in February 2012, while the first version created solely by MIT was launched in March 2012 and upgraded to App Inventor 2 in December 2013.As of 2014, App inventor is now maintained by MIT.
Basic4android
Basic4android is a commercial product similar to Simple.It is inspired by Microsoft Visual Basic 6 and Microsoft Visual Studio. It makes android programming much simpler for regular Visual Basic programmers who find coding in Java difficult. Basic4android is very active, and there is a strong online community of Basic4android developers.Corona SDK
Corona SDK is a software development kit (SDK) created by Walter Luh, Founder of Corona Labs Inc.. Corona SDK allows software programmers to build mobile applications for iPhone, iPad, and Android devices.Corona lets developers use integrated Lua, layered on top of C++/OpenGL, to build graphic applications. The SDK does not charge per-app royalty or impose any branding requirement, and has a subscription-based purchase model.
Delphi
Delphi can also be used for creating Android application. It uses Pascal language, and the latest version is Delphi XE8, developed by Embarcadero.HyperNext Android Creator
HyperNext Android Creator (HAC) is a software development system aimed at beginner programmers that can help them create their own Android apps without knowing Java and the Android SDK. It is based on HyperCard that treated software as a stack of cards with only one card being visible at any one time and so is well suited to mobile phone applications that have only one window visible at a time. HyperNext Android Creator's main programming language is simply called HyperNext and is loosely based on Hypercard's HyperTalk language. HyperNext is an interpreted English-like language and has many features that allow creation of Android applications. It supports a growing subset of the Android SDK including its own versions of the GUI control types and automatically runs its own background service so apps can continue to run and process information while in the background.Kivy
Kivy is an open source Python library for developing multitouch application software with a natural user interface (NUI) for a wide selection of devices. Kivy provides the possibility of maintaining a single application for numerous operating systems ("code once, run everywhere"). Kivy has a custom-built deployment tool for deploying mobile applications called Buildozer, which is available only for Linux. Buildozer is currently alpha software, but is far less cumbersome than older Kivy deployment methods. Applications programmed with Kivy can be submitted to any Android mobile application distribution platform.Lazarus
Lazarus may be used to develop Android applications using Pascal language with Free Pascal compiler starting from version 2.7.1.Processing
The Processing environment, which also uses the Java language, has supported an Android mode since version 1.5; integration with device camera and sensors is possible using the Ketai library.Qt for Android
Qt for Android enables Qt 5 applications to run on devices with Android v2.3.3 (API level 10) or later.Qt is a cross-platform application framework which can target platforms such as Android, Linux, iOS, Sailfish OS and Windows. Qt application development is done in standard C++ and QML, requiring both the Android NDK and SDK.Qt Creator is the integrated development environment provided with the Qt Framework for multi-platform application development.RFO BASIC!
RFO BASIC!, a dialect of Dartmouth Basic, is an on-device interpreter with libraries for access to hardware, sensors, sound, graphics, multitouch, file system, SQLite, networking, HTML GUI, encryption, SMS, phone, email, text-to-speech, voice recognition, GPS and other functions. It is open-source software, and can produce stand-alone APKs.Development of RFO Basic is active as of March 2015.RubyMotion
RubyMotion is a toolchain to write native mobile apps in Ruby. As of version 3.0, RubyMotion supports Android. RubyMotion Android apps can call into the entire set of Java Android APIs from Ruby, can use 3rd-party Java libraries, and are statically compiled into machine code.Saphir
Saphir is a fork of the open source Rebol 3 (R3) interpreter.All R3 functionality, including GUI, graphics, network access, file access, parse, and other core features are portable across Android, Windows, Mac, and Linux platforms, without any changes to source code. Saphir makes use of concise dialect (DSL) code patterns to build graphic user interfaces and to perform common computational operations, with remarkably short and readable code syntax. The trivial size of the interpreter (.5 - 1.5 megabytes) complements Saphir's simple utilitarian design.SDL
The SDL library offers also a development possibility beside Java, allowing the development with C and the simple porting of existing SDL and native C applications. By injection of a small Java shim and JNI the usage of native SDL code is possible,allowing Android ports like e.g. the Jagged Alliance 2 video game.The Simple project
The goal of Simple is to bring an easy-to-learn-and-use language to the Android platform.Simple is a BASIC dialect for developing Android applications. It targets professional and non-professional programmers alike in that it allows programmers to quickly write Android applications that use the Android runtime components.Similar to Microsoft Visual Basic 6, Simple programs are form definitions (which contain components) and code (which contains the program logic). The interaction between the components and the program logic happens through events triggered by the components. The program logic consists of event handlers which contain code reacting to the events.
The Simple project is not very active,the last source code update being in August 2009.
WinDev Mobile
WinDev Mobile is a proprietary IDE created by PC SOFT and is used to create graphical user interface (GUI) applications for smartphones and tablets (including Android devices). It uses the WLanguage as its programming language, which is available in English, French and Chinese.Xamarin
With a C# shared codebase, developers can use Xamarin to write native iOS, Android, and Windows apps with native user interfaces and share code across multiple platforms. Xamarin has over 505,000 developers in more than 120 countries around the world as of February 2014.X11 Basic
X11-Basic is a dialect of the BASIC programming language with graphics capability that integrates features like shell scripting, cgi-Programming and full graphical visualisation into the easy to learn basic language on modern computers. The syntax is most similar to the old GFA-Basic ATARI-ST.Android Developer Challenge
The Android Developer Challenge was a competition to find the most innovative application for Android. Google offered prizes totaling 10 million US dollars, distributed between ADC I and ADC II. ADC I accepted submissions from January 2 to April 14, 2008. The 50 most promising entries, announced on May 12, 2008, each received a $25,000 award to further development.It ended in early September with the announcement of ten teams that received $275,000 each, and ten teams that received $100,000 each.ADC II was announced on May 27, 2009.The first round of the ADC II closed on October 6, 2009.The first-round winners of ADC II comprising the top 200 applications were announced on November 5, 2009. Voting for the second round also opened on the same day and ended on November 25. Google announced the top winners of ADC II on November 30, with SweetDreams, What the Doodle!? and WaveSecure being nominated the overall winners of the challenge.
Community-based firmware
There is a community of open-source enthusiasts that build and share Android-based firmware with a number of customizations and additional features, such as FLAC lossless audio support and the ability to store downloaded applications on the microSD card.This usually involves rooting the device. Rooting allows users root access to the operating system, enabling full control of the phone. Rooting has several disadvantages as well, including increased risk of hacking, high chances of bricking, losing warranty, increased virus attack risks, etc.However, rooting allows custom firmwares to be installed, although the device's bootloader must also be unlocked. Modified firmwares allow users of older phones to use applications available only on newer releases.Those firmware packages are updated frequently, incorporate elements of Android functionality that haven't yet been officially released within a carrier-sanctioned firmware, and tend to have fewer limitations. CyanogenMod and OMFGB are examples of such firmware.
On September 24, 2009, Google issued a cease and desist letter to the modder Cyanogen, citing issues with the re-distribution of Google's closed-source applications within the custom firmware. Even though most of Android OS is open source, phones come packaged with closed-source Google applications for functionality such as the Android Market and GPS navigation. Google has asserted that these applications can only be provided through approved distribution channels by licensed distributors. Cyanogen has complied with Google's wishes and is continuing to distribute this mod without the proprietary software. It has provided a method to back up licensed Google applications during the mod's install process and restore them when the process is complete.
Java standards
Obstacles to development include the fact that Android does not use established Java standards, that is, Java SE and ME. This prevents compatibility between Java applications written for those platforms and those written for the Android platform. Android only reuses the Java language syntax and semantics, but it does not provide the full class libraries and APIs bundled with Java SE or ME.However, there are multiple tools in the market from companies such as Myriad Group and UpOnTek that provide Java ME to Android conversion services.History
The "Sooner" prototype phone,prior to "Dream"
Android was created by the Open Handset Alliance, which is led by Google. The early feedback on developing applications for the Android platform was mixed.Issues cited include bugs, lack of documentation, inadequate QA infrastructure, and no public issue-tracking system. (Google announced an issue tracker on January 18, 2008.)In December 2007, MergeLab mobile startup founder Adam MacBeth stated, "Functionality is not there, is poorly documented or just doesn't work... It's clearly not ready for prime time." Despite this, Android-targeted applications began to appear the week after the platform was announced. The first publicly available application was the Snake game.The Android Dev Phone is a SIM-unlocked and hardware-unlocked device that is designed for advanced developers. While developers can use regular consumer devices purchased at retail to test and use their applications, some developers may choose not to use a retail device, preferring an unlocked or no-contract device.
A preview release of the Android SDK was released on November 12, 2007. On July 15, 2008, the Android Developer Challenge Team accidentally sent an email to all entrants in the Android Developer Challenge announcing that a new release of the SDK was available in a "private" download area. The email was intended for winners of the first round of the Android Developer Challenge. The revelation that Google was supplying new SDK releases to some developers and not others (and keeping this arrangement private) led to widely reported frustration within the Android developer community at the time.
On August 18, 2008, the Android 0.9 SDK beta was released. This release provided an updated and extended API, improved development tools and an updated design for the home screen. Detailed instructions for upgrading are available to those already working with an earlier release.On September 23, 2008, the Android 1.0 SDK (Release 1) was released.According to the release notes, it included "mainly bug fixes, although some smaller features were added." It also included several API changes from the 0.9 version. Multiple versions have been released since it was developed .
========================================================================
SOFTWARE DEVELOPMENT (ANDROID)
Android software development is the process by which new applications are created for the Android operating system. Applications are usually developed in Java programming language using the Android Software Development Kit (SDK), but other development environments are also available.
As of July 2013, more than one million applications have been developed for Android,with over 25 billion downloads.A June 2011 research indicated that over 67% of mobile developers used the platform, at the time of publication.In Q2 2012, around 105 million units of Android smartphones were shipped which acquires a total share of 68% in overall smartphones sale till Q2 2012.
Contents
1 Official development tools1.1 Android SDK
1.1.1 Android Debug Bridge
1.1.2 Fastboot
1.2 Android NDK
1.3 Android Open Accessory Development Kit
2 Third-party development tools
2.1 Android APIMiner
2.2 AndroWish
2.3 App Inventor for Android
2.4 Basic4android
2.5 Corona SDK
2.6 Delphi
2.7 HyperNext Android Creator
2.8 Kivy
2.9 Lazarus
2.10 Processing
2.11 Qt for Android
2.12 RFO BASIC!
2.13 RubyMotion
2.14 Saphir
2.15 SDL
2.16 The Simple project
2.17 WinDev Mobile
2.18 Xamarin
2.19 X11 Basic
3 Android Developer Challenge
4 Community-based firmware
5 Java standards
6 History
Official development tools
Android SDKAndroid software development kit (Android SDK)
Developer(s) Google
Initial release October 2009; 5 years ago
Stable release 24.0.2 / December 2014; 4 months ago
Written in Java
Operating system Cross-platform
Available in English
Type IDE, SDK
Website :-developer.android.com/tools/sdk/eclipse-adt.html, developer.android.com/sdk/index.html
The Android software development kit (SDK) includes a comprehensive set of development tools.These include a debugger, libraries, a handset emulator based on QEMU, documentation, sample code, and tutorials. Currently supported development platforms include computers running Linux (any modern desktop Linux distribution), Mac OS X 10.5.8 or later, and Windows XP or later. As of March 2015, the SDK is not available on Android itself, but the software development is possible by using specialized Android applications.
Until around the end of 2014, the officially supported integrated development environment (IDE) was Eclipse using the Android Development Tools (ADT) Plugin, though IntelliJ IDEA IDE (all editions) fully supports Android development out of the box,and NetBeans IDE also supports Android development via a plugin.As of 2015, Android Studio,made by Google and powered by IntelliJ, is the official IDE; however, developers are free to use others. Additionally, developers may use any text editor to edit Java and XML files, then use command line tools (Java Development Kit and Apache Ant are required) to create, build and debug Android applications as well as control attached Android devices (e.g., triggering a reboot, installing software package(s) remotely).
Enhancements to Android's SDK go hand in hand with the overall Android platform development. The SDK also supports older versions of the Android platform in case developers wish to target their applications at older devices. Development tools are downloadable components, so after one has downloaded the latest version and platform, older platforms and tools can also be downloaded for compatibility testing.
Android applications are packaged in .apk format and stored under /data/app folder on the Android OS (the folder is accessible only to the root user for security reasons). APK package contains .dex files (compiled byte code files called Dalvik executables), resource files, etc.
Android Debug Bridge
The Android Debug Bridge (ADB) is a toolkit included in the Android SDK package. It consists of both client and server-side programs that communicate with one another. The ADB is typically accessed through the command-line interface,although numerous graphical user interfaces exist to control ADB.The format for issuing commands through the ADB is typically:
adb [-d|-e|-s <serialNumber>] <command>
In a security issue reported in March 2011, ADB was targeted as a vector to attempt to install a rootkit on connected phones using a "resource exhaustion attack".
Fastboot
"Fastboot" redirects here. For the PC fast booting ability, see Instant-on.Fastboot is a diagnostic protocol included with the SDK package used primarily to modify the flash filesystem via a USB connection from host computer. It requires that the device be started in a boot loader or Second Program Loader mode in which only the most basic hardware initialization is performed. After enabling the protocol on the device itself, it will accept a specific set of commands sent to it via USB using a command line. Some of the most commonly used fastboot commands include:
flash – rewrites a partition with a binary image stored on the host computer
erase – erases a specific partition
reboot – reboots the device into either the main operating system, the system recovery partition or back into its bootloader
devices – displays a list of all devices (with the serial number) connected to the host computer
format – formats a specific partition; the file system of the partition must be recognized by the device
Android NDK
Android Native Development Kit (Android NDK)
Developer(s) Google
Initial release June 2009; 5 years ago
Stable release 10d / December 2014; 4 months ago
Written in C and C++
Operating system Cross-platform
Available in English
Type IDE, SDK
Website developer.android.com/tools/sdk/ndk/index.html
Libraries written in C, C++ and other languages can be compiled to ARM, MIPS or x86 native code and installed using the Android Native Development Kit (NDK). Native classes can be called from Java code running under the Dalvik VM using the System.loadLibrary call, which is part of the standard Android Java classes.
Complete applications can be compiled and installed using traditional development tools.However, according to the Android documentation, NDK should not be used solely for developing applications only because the developer prefers to program in C/C++, as using NDK increases complexity while most applications would not benefit from using it.
The ADB debugger gives a root shell under the Android Emulator which allows ARM, MIPS or x86 native code to be uploaded and executed. Native code can be compiled using GCC or the Intel C++ Compiler on a standard PC.Running native code is complicated by Android's use of a non-standard C library (libc, known as Bionic). The graphics library that Android uses to arbitrate and control access to this device is called the Skia Graphics Library (SGL), and it has been released under an open source licence.Skia has backends for both Win32 and Unix, allowing the development of cross-platform applications, and it is the graphics engine underlying the Google Chrome web browser.
Unlike Java application development based on an IDE such as Eclipse, the NDK is based on command-line tools and requires invoking them manually to build, deploy and debug the apps. Several third-party tools allow integrating the NDK into Eclipse and Visual Studio.
Android Open Accessory Development Kit
The Android 3.1 platform (also backported to Android 2.3.4) introduces Android Open Accessory support, which allows external USB hardware (an Android USB accessory) to interact with an Android-powered device in a special "accessory" mode. When an Android-powered device is in accessory mode, the connected accessory acts as the USB host (powers the bus and enumerates devices) and the Android-powered device acts as the USB device. Android USB accessories are specifically designed to attach to Android-powered devices and adhere to a simple protocol (Android accessory protocol) that allows them to detect Android-powered devices that support accessory mode.Third-party development tools
Android APIMinerAndroid APIMiner is a platform that automatically instruments the Javadoc documentation of the Android API with examples of usage, extracted from real open-source Android applications.To improve the quality of the extracted examples, APIMiner relies on an intra-procedural static slicing algorithm.
AndroWish
AndroWish is an on-device Tcl/Tk interpreter which provides multi-windows GUI and give access to Bluetooth, USB, network sockets, text-to-speech, speech recognition, sensor, location (GPS or network information), activity manager, SQLite and sound. The GUI layer relies on SDL2. AndroWish is provided with 337 Tcl packages.
App Inventor for Android
On July 12, 2010, Google announced the availability of App Inventor for Android, a Web-based visual development environment for novice programmers, based on MIT's Open Blocks Java library and providing access to Android devices' GPS, accelerometer and orientation data, phone functions, text messaging, speech-to-text conversion, contact data, persistent storage, and Web services, initially including Amazon and Twitter."We could only have done this because Android’s architecture is so open," said the project director, MIT's Hal Abelson.Under development for over a year,the block-editing tool has been taught to non-majors in computer science at Harvard, MIT, Wellesley, Trinity College (Hartford,) and the University of San Francisco, where Professor David Wolber developed an introductory computer science course and tutorial book for non-computer science students based on App Inventor for Android.In the second half of 2011, Google released the source code, terminated its Web service, and provided funding for the creation of The MIT Center for Mobile Learning, led by the App Inventor creator Hal Abelson and fellow MIT professors Eric Klopfer and Mitchel Resnick.Latest version created as the result of Google–MIT collaboration was released in February 2012, while the first version created solely by MIT was launched in March 2012 and upgraded to App Inventor 2 in December 2013.As of 2014, App inventor is now maintained by MIT.
Basic4android
Basic4android is a commercial product similar to Simple.It is inspired by Microsoft Visual Basic 6 and Microsoft Visual Studio. It makes android programming much simpler for regular Visual Basic programmers who find coding in Java difficult. Basic4android is very active, and there is a strong online community of Basic4android developers.Corona SDK
Corona SDK is a software development kit (SDK) created by Walter Luh, Founder of Corona Labs Inc.. Corona SDK allows software programmers to build mobile applications for iPhone, iPad, and Android devices.Corona lets developers use integrated Lua, layered on top of C++/OpenGL, to build graphic applications. The SDK does not charge per-app royalty or impose any branding requirement, and has a subscription-based purchase model.
Delphi
Delphi can also be used for creating Android application. It uses Pascal language, and the latest version is Delphi XE8, developed by Embarcadero.HyperNext Android Creator
HyperNext Android Creator (HAC) is a software development system aimed at beginner programmers that can help them create their own Android apps without knowing Java and the Android SDK. It is based on HyperCard that treated software as a stack of cards with only one card being visible at any one time and so is well suited to mobile phone applications that have only one window visible at a time. HyperNext Android Creator's main programming language is simply called HyperNext and is loosely based on Hypercard's HyperTalk language. HyperNext is an interpreted English-like language and has many features that allow creation of Android applications. It supports a growing subset of the Android SDK including its own versions of the GUI control types and automatically runs its own background service so apps can continue to run and process information while in the background.Kivy
Kivy is an open source Python library for developing multitouch application software with a natural user interface (NUI) for a wide selection of devices. Kivy provides the possibility of maintaining a single application for numerous operating systems ("code once, run everywhere"). Kivy has a custom-built deployment tool for deploying mobile applications called Buildozer, which is available only for Linux. Buildozer is currently alpha software, but is far less cumbersome than older Kivy deployment methods. Applications programmed with Kivy can be submitted to any Android mobile application distribution platform.Lazarus
Lazarus may be used to develop Android applications using Pascal language with Free Pascal compiler starting from version 2.7.1.Processing
The Processing environment, which also uses the Java language, has supported an Android mode since version 1.5; integration with device camera and sensors is possible using the Ketai library.Qt for Android
Qt for Android enables Qt 5 applications to run on devices with Android v2.3.3 (API level 10) or later.Qt is a cross-platform application framework which can target platforms such as Android, Linux, iOS, Sailfish OS and Windows. Qt application development is done in standard C++ and QML, requiring both the Android NDK and SDK.Qt Creator is the integrated development environment provided with the Qt Framework for multi-platform application development.RFO BASIC!
RFO BASIC!, a dialect of Dartmouth Basic, is an on-device interpreter with libraries for access to hardware, sensors, sound, graphics, multitouch, file system, SQLite, networking, HTML GUI, encryption, SMS, phone, email, text-to-speech, voice recognition, GPS and other functions. It is open-source software, and can produce stand-alone APKs.Development of RFO Basic is active as of March 2015.RubyMotion
RubyMotion is a toolchain to write native mobile apps in Ruby. As of version 3.0, RubyMotion supports Android. RubyMotion Android apps can call into the entire set of Java Android APIs from Ruby, can use 3rd-party Java libraries, and are statically compiled into machine code.Saphir
Saphir is a fork of the open source Rebol 3 (R3) interpreter.All R3 functionality, including GUI, graphics, network access, file access, parse, and other core features are portable across Android, Windows, Mac, and Linux platforms, without any changes to source code. Saphir makes use of concise dialect (DSL) code patterns to build graphic user interfaces and to perform common computational operations, with remarkably short and readable code syntax. The trivial size of the interpreter (.5 - 1.5 megabytes) complements Saphir's simple utilitarian design.SDL
The SDL library offers also a development possibility beside Java, allowing the development with C and the simple porting of existing SDL and native C applications. By injection of a small Java shim and JNI the usage of native SDL code is possible,allowing Android ports like e.g. the Jagged Alliance 2 video game.The Simple project
The goal of Simple is to bring an easy-to-learn-and-use language to the Android platform.Simple is a BASIC dialect for developing Android applications. It targets professional and non-professional programmers alike in that it allows programmers to quickly write Android applications that use the Android runtime components.Similar to Microsoft Visual Basic 6, Simple programs are form definitions (which contain components) and code (which contains the program logic). The interaction between the components and the program logic happens through events triggered by the components. The program logic consists of event handlers which contain code reacting to the events.
The Simple project is not very active,the last source code update being in August 2009.
WinDev Mobile
WinDev Mobile is a proprietary IDE created by PC SOFT and is used to create graphical user interface (GUI) applications for smartphones and tablets (including Android devices). It uses the WLanguage as its programming language, which is available in English, French and Chinese.Xamarin
With a C# shared codebase, developers can use Xamarin to write native iOS, Android, and Windows apps with native user interfaces and share code across multiple platforms. Xamarin has over 505,000 developers in more than 120 countries around the world as of February 2014.X11 Basic
X11-Basic is a dialect of the BASIC programming language with graphics capability that integrates features like shell scripting, cgi-Programming and full graphical visualisation into the easy to learn basic language on modern computers. The syntax is most similar to the old GFA-Basic ATARI-ST.Android Developer Challenge
The Android Developer Challenge was a competition to find the most innovative application for Android. Google offered prizes totaling 10 million US dollars, distributed between ADC I and ADC II. ADC I accepted submissions from January 2 to April 14, 2008. The 50 most promising entries, announced on May 12, 2008, each received a $25,000 award to further development.It ended in early September with the announcement of ten teams that received $275,000 each, and ten teams that received $100,000 each.ADC II was announced on May 27, 2009.The first round of the ADC II closed on October 6, 2009.The first-round winners of ADC II comprising the top 200 applications were announced on November 5, 2009. Voting for the second round also opened on the same day and ended on November 25. Google announced the top winners of ADC II on November 30, with SweetDreams, What the Doodle!? and WaveSecure being nominated the overall winners of the challenge.
Community-based firmware
There is a community of open-source enthusiasts that build and share Android-based firmware with a number of customizations and additional features, such as FLAC lossless audio support and the ability to store downloaded applications on the microSD card.This usually involves rooting the device. Rooting allows users root access to the operating system, enabling full control of the phone. Rooting has several disadvantages as well, including increased risk of hacking, high chances of bricking, losing warranty, increased virus attack risks, etc.However, rooting allows custom firmwares to be installed, although the device's bootloader must also be unlocked. Modified firmwares allow users of older phones to use applications available only on newer releases.Those firmware packages are updated frequently, incorporate elements of Android functionality that haven't yet been officially released within a carrier-sanctioned firmware, and tend to have fewer limitations. CyanogenMod and OMFGB are examples of such firmware.
On September 24, 2009, Google issued a cease and desist letter to the modder Cyanogen, citing issues with the re-distribution of Google's closed-source applications within the custom firmware. Even though most of Android OS is open source, phones come packaged with closed-source Google applications for functionality such as the Android Market and GPS navigation. Google has asserted that these applications can only be provided through approved distribution channels by licensed distributors. Cyanogen has complied with Google's wishes and is continuing to distribute this mod without the proprietary software. It has provided a method to back up licensed Google applications during the mod's install process and restore them when the process is complete.
Java standards
Obstacles to development include the fact that Android does not use established Java standards, that is, Java SE and ME. This prevents compatibility between Java applications written for those platforms and those written for the Android platform. Android only reuses the Java language syntax and semantics, but it does not provide the full class libraries and APIs bundled with Java SE or ME.However, there are multiple tools in the market from companies such as Myriad Group and UpOnTek that provide Java ME to Android conversion services.History
The "Sooner" prototype phone,prior to "Dream"
Android was created by the Open Handset Alliance, which is led by Google. The early feedback on developing applications for the Android platform was mixed.Issues cited include bugs, lack of documentation, inadequate QA infrastructure, and no public issue-tracking system. (Google announced an issue tracker on January 18, 2008.)In December 2007, MergeLab mobile startup founder Adam MacBeth stated, "Functionality is not there, is poorly documented or just doesn't work... It's clearly not ready for prime time." Despite this, Android-targeted applications began to appear the week after the platform was announced. The first publicly available application was the Snake game.The Android Dev Phone is a SIM-unlocked and hardware-unlocked device that is designed for advanced developers. While developers can use regular consumer devices purchased at retail to test and use their applications, some developers may choose not to use a retail device, preferring an unlocked or no-contract device.
A preview release of the Android SDK was released on November 12, 2007. On July 15, 2008, the Android Developer Challenge Team accidentally sent an email to all entrants in the Android Developer Challenge announcing that a new release of the SDK was available in a "private" download area. The email was intended for winners of the first round of the Android Developer Challenge. The revelation that Google was supplying new SDK releases to some developers and not others (and keeping this arrangement private) led to widely reported frustration within the Android developer community at the time.
On August 18, 2008, the Android 0.9 SDK beta was released. This release provided an updated and extended API, improved development tools and an updated design for the home screen. Detailed instructions for upgrading are available to those already working with an earlier release.On September 23, 2008, the Android 1.0 SDK (Release 1) was released.According to the release notes, it included "mainly bug fixes, although some smaller features were added." It also included several API changes from the 0.9 version. Multiple versions have been released since it was developed .
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