IBM PC-DOS is the OEM of Microsoft's MS-DOS for the IBM PC Model 5150 and its successors. The history of how PC-DOS came to be the principal Operating System for the PC is a story that has been told many times and a I will supply links at the bottom of this article. This article is mostly on the other story of PC-DOS, the story of the individual versions and how they fit into the history of the various PC models and even it's standard and optional hardware.
PC-DOS 0.90 Beta
The only obtainable beta, that I know of is 0.90. It displays on boot as The IBM Personal Computer DOS Version 1.00 (C) Copyright IBM Corp 1981. Unlike the 1.00 release it does not ask for the date and this is the only major difference that I see between the two.
PC-DOS 1.00 shipped with the early versions of floppy disk equipped PCs. It has only eight tracks instead of the nine tracks on later versions and is a single sided disk. It has a maximum capacity of 160k. One of the significant differences between 1.00 and all other versions is that you are required to enter the date presented as a M-D-Y format unlike later versions where you can type enter to avoid date and time entry (Actually, to enter time you have use the time command from the command prompt, it does not ask you for it at boot.). Most of the file on the disk are either the most basic DOS utilities such as Format and Sys or a quite lengthy selection of Basic demos. Also to note, a lot of traditional features are lacking such as directories, the prompt command, pipes, and the /w and /p switches with dir. Also, the "copy con" method of file creation does not work.
Version 1.10 added quite a few well-known features such as dir's /w and /p switches and on boot up you get the traditional entering of date and time prompts. The copyright date is both 1981 and 1982. As far as I know it also fixed some bugs. Also, of note there are less basic demos than in 1.00.
Version 2.00, in my opinion is the first version of PC-DOS that is truly the descendant of the more modern versions of DOS. It was released as the version designed for the IBM PC XT Model 5160. The main reason for this version was to utilize fixed disks (hard drives). It came on two single-sided, double-density (9-track) floppy disks. Many commands for hard disk operation are present such as fdisk, cd, md, and rd. Also, the autoexec.bat and config.sys files are introduced as well as the prompt command and unlike PC-DOS 1.xx, "copy con" works as expected. It should be noted that this DOS's version of fdisk only supports up to a single 10 MB hard drive. An interesting fact about the format utility for this version is that it does not require a "Y" for confirmation before you format. The copyright date is 1981, 1982, 1983.
Version 2.10 was mostly released for minor bug fixes and the ability to support half-height drives. The most important feature was that it also added support for the IBM PCjr and its special graphics.
PC-DOS 3.00 was released for the support of the IBM Model PC AT Model 5170. Therefore, there were many new features added. First of all, it was released on two double-sided, double-density floppies and this version could support the new 1.2 MB high density floppies as featured on the AT. Also it supported a hard drive with a single partition up to 32 MB. It also supported EGA graphics and was supposed to support networking but this proved to be too buggy so it was shelved until the next release.
Version 3.10 had networking support and had a few bug fixes, besides that, it isn't much different that version 3.00
Version 3.20 had two big improvements. First, it supported the new 720 kb, 3 and a half inch, double-density floppy disk. Second, it supported the IBM PC Convertible Model 5140 which was one of the first PCs to utilize the aforementioned 720 kb floppy disks. Later, 3.20 was used on the IBM PS/2 which utilized these disks as well
The final version of the "classic PC-DOS family," PC-DOS 3.30, had a few major improvements. First, multiple partitions were supported, still up to 32 MB each. Quick anecdote, in the late 80s, most hard drive came in either 20 or 40 MB in size. 32 MB drives were rare. So, using PC-DOS or MS-DOS 3.30 most owners would partition a 40 MB drive into a 32 and an 8 MB partition and largely ignore the 8 MB partition. The reason for this is if you didn't know the ins and out of fdisk, this is how it would partition the drive by default even though if you just either read the documentation or played around with the settings, you would find that you could easily partition it into 2 equal 20 MB partitions. Also, another major feature was support for the 1.44 MB high-density, 3 and a half inch floppy. This was originally in the new generation of Intel 80286 IBM PCs, the PS/2 Model 50 amongst others.
PC-DOS 4.00 and 4.01
These were the beginning of the more modern versions of PC-DOS. The only problem is that the initial version was very buggy. Version 4.01 cleaned up most of the bugs, but the damage had already been done, most people stuck with PC-DOS 3.30. There were two huge improvements though. First, partitions could be up to 2 GB although drives of this size weren't even really available. Second, DOSSHELL was included for the first time and was bundled with all DOS version thereafter. DOSSHELL is quite similar to the Windows 2 DOS Executive but it can't natively run Windows 2 programs, has cleaner fonts, and the directory tree is displayed on the left-hand side.
PC-DOS 5.00, 5.00.1. and 5.02
PC-DOS 5 was everything PC-DOS should have been. It was less buggy and it included EMS memory drivers natively and UMB (Upper Memory Block) support. It also included the QBASIC Basic interpreter and IDE and Microsoft Edit. The 5.00.1 and 5.02 versions were simply bug fixes.
PC-DOS 6.10 and 6.30
These versions of DOS were made completely in-house by IBM. They both included anti-virus, and backup software. Also, Qbasic was dropped and Microsoft Edit was replaced by IBM E editor which in my opinion is superior to Microsoft Edit and is the similar to nano. 6.30 also included SuperStor disk compression.
PC-DOS 7.00 and 2000
These were the final commercially available PC-DOS versions. 7.00 is basically 6.30 plus built-in REXX support. PC-DOS 2000, also known as PC-DOS 7.00 Revision 1. Version 2000 is simply version 7.00 with y2k fixes installed.