AIX is based onUNIX System V with4.3BSD-compatible extensions. It is certified to the UNIX 03 and UNIX V7 specifications of theSingle UNIX Specification, beginning with AIX versions 5.3 and 7.2 TL5, respectively.[6] Older versions were certified to the UNIX 95 and UNIX 98 specifications.[7]
AIX was the first operating system to implement ajournaling file system. IBM has continuously enhanced the software with features such as processor, disk, and networkvirtualization, dynamic hardware resource allocation (including fractional processor units), andreliability engineering concepts derived from itsmainframe designs.[8]
IBMRS/6000 AIX file servers used forIBM.com in the 1990sAIX Version 4 console login prompt
Unix began in the early 1970s atAT&T'sBell Labs research center, running onDECminicomputers. By 1976, the operating system was used in various academic institutions, includingPrinceton University, where Tom Lyon and others ported it to theS/370 to run as a guest OS underVM/370.[9] This port becameAmdahl UTS from IBM's mainframe rival,[10][11] which that company increasingly proritized from the late 1980s.[12]
IBM's involvement with Unix began in 1979 when it assisted Bell Labs in porting Unix to the S/370 platform to be used as abuild host for the5ESS switch's software. During this process, IBM made modifications to theTSS/370 Resident Supervisor to better support Unix.[13]
In 1984, IBM introduced its own Unix variant for the S/370 platform called VM/IX, developed byInteractive Systems Corporation (ISC) using Unix System III. However, VM/IX was only available as a PRPQ (Programming Request for Price Quotation) and was not a General Availability product.
By 1985 most computer companies offered Unix alongside their proprietary operating systems.[14] Although an industry analyst that year described IBM as not enthusiastic about Unix,[15] the company replaced VM/IX in 1985 with IBM IX/370, a fully supported product based on AT&T's Unix System V, intended to compete against UTS[16] and also developed by ISC.[17]
ISC also developed AIX for theIBM RT PC workstation, introduced in January 1986, based onUNIX System V Releases 1 and 2, and incorporating source code from 4.2 and 4.3BSD UNIX.[17][18] AIX Version 2 followed in 1987 for the RT PC.[19]
In 1990, AIX Version 3 was released for the newPOWER-basedRS/6000 platform.[20] Observers said that year that IBM had officially approved Unix, with the company willing to let its proprietaryAS/400 and Unix-based RS/6000 compete against each other in themidrange system market.[21] AIX was the primary operating system for the RS/6000 series, which was later renamedIBM eServer pSeries,IBM System p, and finallyIBM Power Systems.
AIX Version 4, introduced in 1994, addedsymmetric multiprocessing and evolved through the 1990s, culminating with AIX 4.3.3 in 1999. A modified version of Version 4.1 was also used as the standard OS for theApple Network Server line byApple Computer.
In the late 1990s, underProject Monterey, IBM and theSanta Cruz Operation attempted to integrate AIX andUnixWare into a multiplatform Unix forIntelIA-64 architecture. The project was discontinued in 2002 after limited commercial success.[22]
In 2003, theSCO Group filed a lawsuit against IBM, alleging misappropriation ofUNIX System V source code in AIX. The case was resolved in 2010 when a jury ruled thatNovell owned the rights to Unix, not SCO.[22]
AIX 7.1 was released in September 2010 with enhancements such as Cluster Aware AIX and support for large-scale memory and real-time application requirements.[23]
The original AIX (sometimes calledAIX/RT) was developed for the IBM RT PC workstation by IBM in conjunction with ISC,[17] which had previously portedUNIX System III to theIBM PC for IBM asPC/IX.[24] According to its developers, the original AIX source consists of one million lines of code.[17] Installation media consists of eight1.2M floppy disks. The RT was based on theIBM ROMPmicroprocessor, the first commercialRISC chip, based onIBM Research'sIBM 801).
One of the novel aspects of the RT design is the use of amicrokernel, called Virtual Resource Manager (VRM). The keyboard, mouse, display, disk drives and network are all controlled by a microkernel. One can "hotkey" from one operating system to the next using the Alt-Tab key combination. Each OS in turn gets possession of the keyboard, mouse and display. Besides AIX v2, thePICK OS also includes this microkernel.
Much of the AIX v2 kernel was written in thePL.8 programming language, which proved troublesome during the migration to AIX v3.[citation needed] AIX v2 includes fullTCP/IP networking, as well asSNA and two networking file systems:NFS, licensed fromSun Microsystems, andDistributed Services (DS). DS has the distinction of being built on top of SNA, and thereby being fully compatible with DS onIBM mainframe systems[clarification needed] and on midrange systems runningOS/400 throughIBM i. For the graphical user interfaces, AIX v2 comes with the X10R3 and later the X10R4 and X11 versions of theX Window System from MIT, with theAthena widget set. Compilers forFortran andC were available.
AIX PS/2 (also known asAIX/386) was developed byLocus Computing Corporation under contract to IBM.[24] AIX PS/2, first released in October 1988,[25] runs onIBM PS/2 personal computers withIntel 386 and compatible processors.
AIX PS/2 1.3 AIXwindows Desktop
The product was announced in September 1988 with a baseline tag price of $595, although some utilities, such asUUCP, were included in a separate Extension package priced at $250.nroff andtroff for AIX were also sold separately in a Text Formatting System package priced at $200. TheTCP/IP stack for AIX PS/2 retailed for another $300. TheX Window System package was priced at $195, and has a graphical environment called theAIXwindows Desktop, based onIXI'sX.desktop.[26] The C and FORTRAN compilers each had a price tag of $275. Locus also made available theirDOS Merge virtual machine environment for AIX, which can run MS DOS 3.3 applications inside AIX; DOS Merge was sold separately for another $250.[27] IBM also offered a $150 AIX PS/2 DOS Server Program, which providedfile server andprint server services for client computers running PC DOS 3.3.[28]
The last version of PS/2 AIX is 1.3. It was released in 1992 and announced to add support for non-IBM (non-microchannel) computers as well.[29] Support for PS/2 AIX ended in March 1995.[30]
In 1988, IBM announcedAIX/370,[31] also developed by Locus. AIX/370 was IBM's fourth attempt to offerUnix-like functionality for their mainframe line, specifically theSystem/370 (the prior versions were aTSS/370-based Unix system developed jointly with AT&T c.1980,[13] aVM/370-based system namedVM/IX developed jointly with ISC c.1984,[citation needed] and aVM/370-based version of TSS/370[citation needed] namedIX/370 which was upgraded to be compatible withUNIX System V[citation needed]). AIX/370 was released in 1990 with functional equivalence to System V Release 2 and 4.3BSD as well as IBM enhancements. With the introduction of theESA/390 architecture, AIX/370 was replaced byAIX/ESA[32] in 1991 based onOSF/1, and also runs on theSystem/390 platform. Unlike AIX/370, AIX/ESA runs both natively as the host operating system, and as a guest underVM. AIX/ESA, while technically advanced, had little commercial success, partially because[citation needed] UNIX functionality was added as an option to the existing mainframe operating system,MVS, asMVS/ESA SP Version 4 Release 3 OpenEdition[33] in 1994, and continued as an integral part of MVS/ESA SP Version 5, OS/390 and z/OS, with the name eventually changing fromOpenEdition toUnix System Services. IBM also provided OpenEdition in VM/ESA Version 2[34] through z/VM.
As part ofProject Monterey, IBM released abeta test version of AIX 5L for the IA-64 (Itanium) architecture in 2001, but this never became an official product due to lack of interest.[35]
TheApple Network Server (ANS) systems are PowerPC-based systems designed byApple Computer to have numerous high-end features that contemporary standard Apple hardware does not have, including swappable hard drives, redundant power supplies, and external monitoring capability. These systems are more or less based on thePower Macintosh hardware available at the time but designed to use AIX (versions 4.1.4 or 4.1.5) as their native operating system in a specialized version specific to the ANS called AIX for Apple Network Servers.
AIX is only compatible with the Network Servers and was not ported to standard Power Macintosh hardware. It should not be confused withA/UX, Apple's earlier version of Unix for68k-basedMacintoshes.
The release of AIX version 3 (sometimes calledAIX/6000) coincided with the announcement of the firstPOWER1-based IBMRS/6000 models in 1990.
AIX v3 innovated in several ways on the software side. It is the first operating system to introduce the idea of ajournaling file system,JFS, which allows for fast boot times by avoiding the need to ensure the consistency of the file systems on disks (seefsck) on every reboot. Another innovation isshared libraries which avoid the need for static linking from an application to the libraries it used. The resulting smaller binaries use less of the hardware RAM to run, and used less disk space to install. Besides improving performance, executable binaries can be in the tens ofkilobytes instead of a megabyte for an executable statically linked to theC library. AIX v3 also scrapped the microkernel of AIX v2, a contentious move that resulted in v3 containing noPL.8 code and being somewhat more "pure" than v2.
Other notable subsystems include:
IRIS GL, a 3D rendering library, the progenitor ofOpenGL. IRIS GL was licensed by IBM fromSGI in 1987, a small company, which had sold only a few thousand machines at the time. SGI also provided the low-end graphics card for the RS/6000, capable of drawing 20,000gouraud-shaded triangles per second. The high-end graphics card was designed by IBM, a follow-on to the mainframe-attachedIBM 5080, capable of rendering 990,000 vectors per second.
DPS on-screen display system as an alternative if the X11+Motif combination failed in the marketplace. However, it is highly proprietary, supported only by Sun,NeXT, and IBM. This, and lack of 3D capability, caused it to fail in the marketplace versus X11+Motif and its lack of 3D capability.
In addition, AIX applications can run in thePASE subsystem underIBM i.
IBM made the AIX for RS/6000 source code available to customers for a fee; in 1991, IBM customers could order the AIX 3.0 source code for a one-time charge of US$60,000;[36] subsequently, IBM released the AIX 3.1 source code in 1992,[37] and AIX 3.2 in 1993.[38] These source code distributions exclude certain files (authored by third-parties) which IBM did not have rights to redistribute, and also exclude layered products such as the MS-DOS emulator and the C compiler. To license the AIX source code the customer first had to procure source code license agreements with AT&T and theUniversity of California, Berkeley.[36]
LVM (Logical Volume Manager) was incorporated into OSF/1, and in 1995 for HP-UX,[57] and the Linux LVM implementation is similar to the HP-UX LVM implementation.[58]
SMIT is the System Management Interface Tool for AIX. It allows a user to navigate a menu hierarchy of commands, rather than using the command line. Invocation is typically achieved with the commandsmit. Experienced system administrators make use of theF6 function key which generates the command line that SMIT will invoke to complete it.SMIT also generates a log of commands that are performed in thesmit.script file. Thesmit.script file automatically records the commands with the command flags and parameters used. Thesmit.script file can be used as an executable shell script to rerun system configuration tasks. SMIT also creates thesmit.log file, which contains additional detailed information that can be used by programmers in extending the SMIT system.
smit andsmitty refer to the same program, thoughsmitty invokes the text-based version, whilesmit will invoke an X Window System based interface if possible; however, ifsmit 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 theDISPLAY variable.[citation needed]
Object Data Manager (ODM) is a database of system information integrated into AIX,[62][63] analogous to theregistry inMicrosoft Windows.[64] A good understanding of the ODM is essential for managing AIX systems.[65]
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^abcdBabcock, Charles (January 27, 1986)."IBM unveils RISC system".Computerworld. Vol. XX, no. 4. pp. 1, 8. RetrievedMay 29, 2025.
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^Scott Vetter, Navdeep Dhaliwal, Ahmed Mashhour, Armin Röll, Liviu Rosca (February 4, 2020)."Chapter 2.2 AIX Secure boot".IBM AIX Enhancements and Modernization. IBM Redbooks.ISBN978-0738458281.Archived from the original on April 12, 2022. RetrievedSeptember 25, 2020.{{cite book}}: CS1 maint: multiple names: authors list (link)
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