Editing IBM PC DOS (section)

== Versions ==

=== {{anchor|1.00|1.10}}PC DOS 1.x ===
<!-- What about PC DOS 1.05 and 1.85? Did they really exist? -->
[[File:IBM DOS 1.1 Manual and Disk.jpg|thumb|upright | User manual and diskette for IBM PC&nbsp;DOS 1.1]]
Microsoft first licensed,<ref name="86-DOS_License"/> then purchased<ref name="86-DOS_Sale"/> [[86-DOS]] from [[Seattle Computer Products]] (SCP), which was modified for the IBM PC by Microsoft employee [[Bob O'Rear]] with assistance from SCP (later Microsoft) employee [[Tim Paterson]].<ref name="Paterson_2007"/> O'Rear got 86-DOS to run on the prototype PC in February 1981. 86-DOS had to be converted from 8-inch to 5.25-inch [[floppy disks]] and integrated with the [[BIOS]], which Microsoft was helping IBM to write.<ref name="Beley_1986"/><ref name="Duncan_1988"/> IBM had more people writing requirements for the computer than Microsoft had writing code. O'Rear often felt overwhelmed by the number of people he had to deal with at the ESD (Entry Systems Division) facility in [[Boca Raton, Florida]].

Perhaps the first public mention of the operating system was in July 1981, when ''[[Byte (magazine)|Byte]]'' discussed rumors of a forthcoming personal computer with "a CP/M-like DOS ... to be called, simply, 'IBM Personal Computer DOS{{'"}}.<ref name="Morgan_1981"/> 86-DOS was [[rebranded]] IBM PC&nbsp;DOS 1.0 for its August 1981 release with the IBM PC. The initial version of DOS was largely based on [[CP/M-80]] 1.x and most of its architecture, function calls and file-naming conventions were copied directly from the older OS. The most significant difference was the fact that it introduced a different file system, [[FAT12]]. Unlike all later DOS versions, the {{mono|[[DATE (DOS command)|DATE]]}} and {{mono|[[TIME (DOS command)|TIME]]}} commands were separate executables rather than part of {{mono|[[COMMAND.COM]]}}. Single-sided 160 [[kilobyte]] (KB) 5.25-inch floppies were the only disk format supported.

In late 1981, Paterson, now at Microsoft, began writing PC&nbsp;DOS 1.10. It debuted in May 1982 along with the Revision&nbsp;B IBM PC. Support for the new double-sided drives was added, allowing 320&nbsp;KB per disk. A number of bugs were fixed, and error messages and prompts were made less cryptic. The {{mono|[[DEBUG (DOS command)|DEBUG.EXE]]}} was now able to load files greater than 64&nbsp;KB in size.

=== {{anchor|2.00|2.10|2.11}}PC DOS 2.x ===

Later, a group of Microsoft programmers (primarily [[Paul Allen]], [[Mark Zbikowski]] and [[Aaron R. Reynolds|Aaron Reynolds]])<ref name="Duncan_1988"/> began work on PC&nbsp;DOS 2.0. Completely rewritten, DOS 2.0 added subdirectories and hard disk support for the new [[IBM Personal Computer XT|IBM XT]], which debuted in March 1983. A new 9-sector format bumped the capacity of floppy disks to 360&nbsp;KB. The [[Unix]]-inspired kernel featured [[file handle]]s in place of the CP/M-derivative file control blocks and loadable device drivers could now be used for adding hardware beyond that which the IBM PC BIOS supported. BASIC and most of the utilities provided with DOS were substantially upgraded as well. A major undertaking that took almost 10 months of work, DOS 2.0 was more than twice as big as DOS 1.x, occupying around 28&nbsp;KB of RAM compared to the 12&nbsp;KB of its predecessor. It would form the basis for all Microsoft consumer-oriented OSes until 2001, when [[Windows XP]] (based on [[Windows NT]]) was released.<ref name="Duncan_1988"/>

In October 1983 (officially 1 November 1983)<ref name="DOS21"/> DOS 2.1 debuted. It fixed some bugs and added support for half-height floppy drives and the new [[IBM PCjr]].

In 1983, [[Compaq]] released the [[Compaq Portable]], the first 100% [[IBM PC compatible]] and licensed their own OEM version of 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.

=== {{anchor|3.00|3.10|3.20|3.21|3.30}}PC DOS 3.x ===
[[File:IBM DOS 3.30 Retail Box.jpg|thumb|Retail box of IBM PC DOS 3.30]]
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.<ref name="Wallace_1992"/> PC&nbsp;DOS 3.1 (released March 1985) fixed the bugs in DOS 3.00 and supported IBM's Network Adapter card on the [[IBM PC Network]]. PC&nbsp;DOS 3.2 added support for {{frac|3|1|2}}-inch double-density 720&nbsp;KB floppy disk drives, supporting the [[IBM PC Convertible]], IBM's first computer to use {{frac|3|1|2}}-inch floppy disks, released April 1986, and later the [[IBM Personal System/2]] in 1987.

In June 1985, IBM and Microsoft signed a long-term Joint Development Agreement to share specified DOS code and create a new operating system from scratch, known at the time as Advanced DOS. On 2 April 1987 [[OS/2]] was announced as the first product produced under the agreement.<ref name="Necasek_2004"/> At the same time, IBM released its next generation of personal computers, the [[IBM Personal System/2]] (PS/2).<ref name="Wallace_1992"/> PC&nbsp;DOS 3.3, released with the PS/2 line, added support for high density {{frac|3|1|2}}-inch 1.44&nbsp;MB floppy disk drives, which IBM introduced in its 80286-based and higher PS/2 models. The upgrade from DOS 3.2 to 3.3 was completely written by IBM, with no development effort on the part of Microsoft, who were working on "Advanced DOS 1.0". DOS 3.30 was the last version designed with the IBM XT and floppy-only systems in mind; it became one of the most popular versions and many users preferred it to its buggy successor.

=== {{anchor|3.40|4.00|4.01|4.02|Lifeboat|Captain|Jetski}}PC DOS 4.x ===

PC&nbsp;DOS 4.0 (internally known as DOS 3.4 originally) shipped July 1988. DOS 4.0 had some compatibility issues with low-level disk utilities due to some internal data structure changes. DOS 4.0 used more memory than DOS 3.30 and it also had a few glitches. Newly added EMS drivers were only compatible with IBM's EMS boards and not the more common{{Citation needed|date=April 2012}} Intel and AST ones. DOS 4.0 is also notable for including the first version of the [[DOS Shell]], a full-screen utility designed to make the command-line OS more user-friendly. Microsoft took back control of development and released a bug-fixed DOS 4.01.<ref name="TackTech"/>

=== {{anchor|5.00|5.01|5.02}}PC DOS 5 ===

DOS 5 debuted in June 1991. DOS 5 supported the use of the [[High Memory Area]] (HMA) and [[Upper Memory Blocks]] (UMBs) on 80286 and later systems to reduce its [[conventional memory]] usage. Also all DOS commands now supported the {{mono|/?}} option to display command syntax. Aside from IBM's PC&nbsp;DOS, MS-DOS was the only other version available as OEM editions vanished since by this time PCs were 100% compatible so customizations for hardware differences were no longer necessary.

The POWER.EXE was introduced that has the [[Advanced Power Management|APM]] standard in version 5.02.<ref>Intel Corporation, "NewsBit: Microsoft, Intel Develop Power Standard", Microcomputer Solutions, March/April 1992, page 1</ref><ref>[https://www.pcjs.org/software/pcx86/sys/dos/ibm/5.02/ IBM PC DOS 5.02]</ref>

This was the last version of DOS that IBM and Microsoft shared the full code for, and the DOS that was integrated into OS/2 2.0's, and later Windows NT's, [[virtual DOS machine]].

=== {{anchor|6.10}}PC DOS 6.1 ===

PC&nbsp;DOS remained a rebranded version of MS-DOS until 1993. IBM and Microsoft parted ways&mdash;MS-DOS 6 was released in March, and PC&nbsp;DOS 6.1 (separately developed) followed in June. Most of the new features from MS-DOS 6.0 appeared in PC&nbsp;DOS 6.1 including the new boot menu support and the new commands {{mono|[[CHOICE (DOS command)|CHOICE]]}}, {{mono|[[DELTREE]]}}, and {{mono|[[MOVE (DOS command)|MOVE]]}}. [[QBasic]] was dropped and the [[MS-DOS Editor]] was replaced with the IBM [[E (PC DOS)|E Editor]]. It also licensed components of [[Central Point Software|Central Point's]] [[PC Tools (software)|PC Tools]], such as Central Point Backup Utility (CPBACKUP).<ref name="version-6.1" /><ref name="version-7" /> PC&nbsp;DOS 6.1 reports itself as DOS 6.00.

=== {{anchor|6.30}}PC DOS 6.3 ===

PC&nbsp;DOS 6.3 followed in December. PC&nbsp;DOS 6.3 was also used in OS/2 for the [[PowerPC]]. PC&nbsp;DOS 6.3 also featured [[SuperStor]] disk compression technology from [[Addstor, Inc.|Addstor]].

=== {{anchor|7.00}}PC DOS 7 ===

PC&nbsp;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, [[IBM Extended Density Format|XDF]], which extended a standard 1.44&nbsp;MB floppy disk to 1.86&nbsp;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&nbsp;DOS 7 also included many optimizations to increase performance and reduce memory usage.<ref name="retro"/>

=== {{anchor|2000}}PC DOS 2000 ===

The most recent retail release was PC&nbsp;DOS 2000 &ndash; released from Austin in 1998 &ndash; which found its niche in the [[embedded software]] market and elsewhere. PC&nbsp;DOS 2000 is a [[Slipstream (computing)|slipstream]] of 7.0 with [[Year 2000 problem|Y2K]] and other fixes applied. To applications, PC&nbsp;DOS 2000 reports itself as "IBM PC&nbsp;DOS 7.00, revision 1", in contrast to the original PC&nbsp;DOS 7, which reported itself as "IBM PC&nbsp;DOS 7.00, revision 0".<ref group="nb" name="NB_OEM"/>

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&nbsp;DOS 2000 in their legacy ''Drive Fitness Test'' (4.15) and ''Hitachi Feature Tool'' (2.15) until 2009.<ref name="HGST_2009"/> [[ThinkPad]] products had a copy of the latest version of PC&nbsp;DOS in their Rescue and Recovery partition.<ref name="Lenovo"/>

=== {{anchor|7.10|PC DOS 7.10}}PC DOS 7.1 ===

PC&nbsp;DOS 7.1 added support for [[Logical Block Addressing]] (LBA) and [[FAT32]] partitions.<ref group="nb" name="NB_OEM"/> Various builds [[Timeline of DOS operating systems|from 1999 up to 2003]] were not released in retail, but used in products such as the IBM ServerGuide Scripting Toolkit.<ref name="IBM_ServerGuide"/> A build of this version of DOS appeared in [[Norton Ghost]] from [[NortonLifeLock|Symantec]].<ref name="Symantec_Ghost"/> Version 7.1 indicates support for FAT32 also in [[MS-DOS]].<ref name="retro"/>

Most builds of this version of DOS are limited to the kernel files {{mono|[[IBMBIO.COM]]}}, {{mono|[[IBMDOS.COM]]}}, and {{mono|[[COMMAND.COM]]}}. The updated programs {{mono|FDISK32}} and {{mono|FORMAT32}} allow one to prepare FAT32 disks. Additional utilities are taken from PC&nbsp;DOS 2000, where needed.