IBM PC DOS

The IBM task force assembled to develop the IBM PC decided that critical components of the machine, including the operating system, would come from outside vendors. This radical break from company tradition of in-house development was one of the key decisions that made the IBM PC an industry standard. Microsoft, founded five years earlier by Bill Gates, was eventually selected for the operating system. IBM wanted Microsoft to retain ownership of whatever software it developed, and wanted nothing to do with helping Microsoft, other than making suggestions from afar. According to task force member Jack Sams: The reasons were internal. We had a terrible problem being sued by people claiming we had stolen their stuff. It could be horribly expensive for us to have our programmers look at code that belonged to someone else because they would then come back and say we stole it and made all this money. We had lost a series of suits on this, and so we didn't want to have a product which was clearly someone else's product worked on by IBM people. We went to Microsoft on the proposition that we wanted this to be their product. IBM first contacted Microsoft to look the company over in July 1980. Negotiations continued over the months that followed, and the paperwork was officially signed in early November. Although IBM expected that most customers would use PC DOS, the IBM PC also supported CP/M-86, which became available six months after PC DOS, and UCSD p-System operating systems. IBM's expectation proved correct: one survey found that 96.3% of PCs were ordered with the $40 PC DOS compared to 3.4% with the $240 CP/M-86. Over the history of IBM PC DOS, various versions were developed by IBM and Microsoft. By the time PC DOS 3.0 was completed, IBM had a team of developers covering the full OS. At that point in time, either IBM or Microsoft completely developed versions of IBM PC DOS going forward. By 1985, the joint development agreement (JDA) between IBM and Microsoft for the development of PC DOS had each company giving the other company a completely developed version. Most of the time branded versions were identical, but there were some cases in which each of the companies made minor modifications to their version of DOS. In the fall of 1984, IBM gave all the source code and documentation of the internally developed IBM TopView for DOS to Microsoft so that Microsoft could more fully understand how to develop an object-oriented operating environment, overlapping windows (for its development of Windows 2.0) and multitasking. Version history == Versions ==

PC DOS 1.x Microsoft first licensed, its own OEM version of MS-DOS 1.10 (quickly replaced by DOS 2.00) from Microsoft. Other PC compatibles followed suit, most of which included hardware-specific DOS features, although some were generic. PC DOS 3.x In August 1984, IBM introduced the Intel 80286-derived IBM PC/AT, its next-generation machine. Along with this was DOS 3.00. Despite jumping a whole version number, it again proved little more than an incremental upgrade, adding nothing more substantial than support for the AT's new 1.2 megabyte (MB) floppy disks. Planned networking capabilities in DOS 3.00 were judged too buggy to be usable and Microsoft disabled them prior to the OS's release. In any case, IBM's original plans for the AT had been to equip it with a proper next-generation OS that would use its extended features, but this never materialized. This was the last version of DOS that IBM and Microsoft shared the full code. This was the DOS integrated into the virtual DOS machine of OS/2 2.0 and later Windows NT. PC DOS 6.1 PC DOS remained a rebranded version of MS-DOS until 1993 when IBM and Microsoft parted ways. MS-DOS 6 was released in March, and PC DOS 6.1 (separately developed) followed in June. Most of the new features from MS-DOS 6.0 appeared in PC DOS 6.1 including new boot menu support and new commands , , and . QBasic was dropped. MS-DOS Editor was replaced with the IBM E Editor. It also licensed components of Central Point's PC Tools, such as Central Point Backup Utility (CPBACKUP). PC DOS 6.1 reports itself as DOS 6.00. PC DOS 6.3 PC DOS 6.3 followed in December. PC DOS 6.3 was also used in OS/2 for the PowerPC. PC DOS 6.3 also featured SuperStor disk compression technology from Addstor. PC DOS 7 PC DOS 7 was released in April 1995 and was the last release of DOS before IBM software development (other than the development IBM ViaVoice) moved to Austin. The REXX programming language was added, as well as support for a new floppy disk format, XDF, which extended a standard 1.44 MB floppy disk to 1.86 MB. SuperStor disk compression technology was replaced with Stac Electronics' STACKER. An algebraic command line calculator and a utility program to load device drivers from the command line were added. PC DOS 7 also included many optimizations to increase performance and reduce memory usage. PC DOS 2000 The most recent retail release was PC DOS 2000 – released from Austin in 1998 – which found its niche in the embedded software market and elsewhere. PC DOS 2000 is a slipstream of 7.0 with Y2K and other fixes applied. To applications, PC DOS 2000 reports itself as "IBM PC DOS 7.00, revision 1", in contrast to the original PC DOS 7, which reported itself as "IBM PC DOS 7.00, revision 0". PC-DOS 2000 was the last version of IBM PC-DOS that was sold at retail. IBM advertised it as a Y2K compliant DOS. As it reports itself as "IBM PC-DOS 7 Revision 1", it is often referred to as "IBM PC-DOS7R1" or just "PC-DOS7R1". Hitachi used PC DOS 2000 in their legacy Drive Fitness Test (4.15) and Hitachi Feature Tool (2.15) until 2009. ThinkPad products had a copy of the latest version of PC DOS in their Rescue and Recovery partition. PC DOS 7.1 PC DOS 7.1 added support for Logical Block Addressing (LBA) and FAT32 partitions. Various builds from 1999 up to 2003 were not released in retail, but instead used in products such as the IBM ServerGuide Scripting Toolkit. A build of this version of DOS appeared in Norton Ghost from Symantec. Version 7.1 indicates support for FAT32 also in MS-DOS. Most builds of this version of DOS are limited to the kernel files , , and . The updated programs and allow one to prepare FAT32 disks. Additional utilities are taken from PC DOS 2000, where needed. == PC DOS as a distributed file client ==

In 1986, IBM announced PC DOS support for client access to the file services defined by Distributed Data Management Architecture (DDM). This enabled programs on PCs to create, manage, and access record-oriented files available on IBM System/36, IBM System/38 and IBM mainframe computers running CICS. In 1988, client support for stream-oriented files and hierarchical directories was added to PC DOS when they became available on the DDM server systems. == See also ==