Software that controls the operation of a computer, directs the input and output of data, keeps track of files, and controls the processing of computer programs. Its roles include managing the functioning of the computer hardware, running the applications programs, serving as an interface between the computer and the user, and allocating computer resources to various functions. When several jobs reside in the computer simultaneously and share resources (multitasking), the OS allocates fixed amounts of CPU time and memory in turn or allows one job to read data while another writes to a printer and still another performs computations. Through a process called time-sharing, a large computer can handle interaction with hundreds of users simultaneously, giving each the perception of being the sole user. Modern computer operating systems are becoming increasingly machine-independent, capable of running on any hardware platform; a widely used platform-independent operating system in use today on mainframe computers is UNIX. Most personal computers run on Microsoft's Windows operating system, which grew out of and eventually replaced MS-DOS. Seealso Linux.
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AIX runs on up to 64 IBM POWER or PowerPC architecture central processing units and two terabytes (TB) of random access memory. The JFS2 file system—first introduced by IBM as part of AIX—allows computer files and partitions over 16 TB in size.
Among other variants, IBM later produced AIX Version 3 (also known as AIX/6000), based on System V Release 3, for their IBM POWER-based RS/6000 platform. Since 1990, AIX has served as the primary operating system for the RS/6000 series (later renamed IBM eServer pSeries, then IBM System p, and now IBM Power Systems). AIX Version 4, introduced in 1994, added symmetric multiprocessing with the introduction of the first RS/6000 SMP servers and continued to evolve though the 1990s, culminating with AIX 4.3.3 in 1999. Version 4.1, in a slightly modified form, was also the standard operating system for the Apple Network Server systems sold by Apple Computer to complement the Macintosh line.
In the late 1990s, under Project Monterey, IBM and the Santa Cruz Operation planned to integrate AIX and UnixWare into a single 32-bit/64-bit multiplatform UNIX with particular emphasis on running on Intel IA-64 architecture CPUs. A beta test version of AIX 5L for IA-64 systems was released, but according to documents released in SCO vs. IBM, less than forty licenses for the finished Monterey Unix were ever sold before the project was terminated in 2002.
AIX 6 was announced in May of 2007 and ran an open beta from June 2007 until the general availability (GA) of AIX 6.1 on November 9th, 2007. Major new features in AIX 6.1 included full role-based access control, workload partitions (which enable application mobility), and live partition mobility on the POWER6 hardware.
On 2007-08-10 the U.S. district court ruled that SCO does not own the copyrights to the Unix operating system.
One of the novel aspects of the RT design was the use of a microkernel, called Virtual Resource Manager (VRM). The keyboard, mouse, display, disk drives and network were all controlled by a microkernel One could "hotkey" from one operating system to the next using the Alt-Tab key combination. Each OS in turn would get possession of the keyboard, mouse and display. Besides AIX v2, the PICK OS also utilized this microkernel.
Much of the AIX v2 kernel was written in the PL/I programming language, which proved troublesome during the migration to AIX v3. AIX v2 included full TCP/IP networking, as well as SNA and two networking file systems: NFS, licensed from Sun Microsystems, and Distributed Services (DS). DS had the distinction of being built on top of SNA, and thereby being fully compatible with DS on the IBM midrange AS/400 and mainframe systems. For the graphical user interfaces, AIX v2 came with the X10R3 and later the X10R4 and X11 versions of the X Window System from MIT, together with the Athena widget set. Compilers for Fortran and C were available. One of the more popular desktop applications was the PageMaker desktop publishing software.
Releases of AIX version 3 also took advantage of the developments in the POWER architecture.
AIX v3 innovated in several ways on the software side. It was the first operating system to introduce the idea of a journalling file system, JFS, which allowed for fast boot times by avoiding the need to fsck the disks on every reboot. Another innovation was the introduction of shared libraries, which avoided the need for an application to statically link to the libraries it used. The resulting smaller binaries used less of the hardware RAM, to run, and used less of the disk space to install. Besides improving performance, it was a boon to developers: executable binaries could be in the 10s of kilobytes instead of a megabyte for an executable statically linked to the C library. AIX v3 also ditched the microkernel of AIX v2, a contentious move that resulted in v3 being somewhat more "pure" (and containing no PL/1 code) than v2.
Other notable subsytems included:
smit. Experienced system administrators make use of the
F6function key which generates the command line that SMIT will invoke to complete the proposed task.
SMIT also generates a log of commands that are performed in the
smit.script file. The
smit.script file automatically records the commands with the command flags and parameters used. The
smit.script file can be used as an executable shell script to rerun system configuration tasks. SMIT also creates the
smit.log file, which contains additional detailed information that can be used by programmers in extending the SMIT system.
smitty refer to the same program, though
smitty invokes the text-based version, while
smit will invoke an X Window System based interface if possible; however, if
smit determines that X Window System capabilities are not present, it will present the text-based version instead of failing. Determination of X Window System capabilities is typically performed by checking for the existence of the