A Historic Diskette
The launch of the IBM 5150, known worldwide as the IBM PC, marked the debut of the PC DOS 1.0 operating system, created by Microsoft from SCP's 86-DOS. The folks at the OS/2 Museum received an old diskette at the end of May, and inside they found what appears to be a preview of PC DOS 1.0, dated June 1981. This detail makes it the oldest IBM PC-compatible operating system in existence, and it's now available in an online emulator.
A Glimpse into the Past
The last standalone version of MS-DOS was 6.22, but the operating system had to travel a long and controversial path before reaching that point. Its story is fascinating no matter how you look at it, with agreements, licenses, acquisitions, accusations of theft, and much more. Some of its oldest variants can be obtained relatively easily on the Web, and Microsoft isn't actively preventing it, so to speak, but as we approach its origins, the search gets more complex. In the last days of May, the OS/2 Museum obtained an old diskette. The complete image is 160 kilobytes, and when they loaded it, they discovered it was a very special copy of PC DOS.
A Preview or Release Candidate?
The operating system presents as PC DOS 1.0, however, the most recent file has a date of June 5, 1981 (two months before its official launch), and the boot sector analysis reports “7-may-81”. All the main files are there, although they are older and smaller compared to those in the final build, so it's not far-fetched to imagine this copy is actually a preview or Release Candidate. In May 1981, PC DOS was barely a rumor, and adjustments to its code extended until the last moment (IBM requested hundreds of changes but never intended to take intellectual control).
Notable Limitations
Even if you have previous experience with MS-DOS, you will notice that this build of PC DOS loads with very important limitations. First, there is no support for directories or .exe files. Second, date and time are independent programs. And third, several commands are missing, such as cls and prompt. The image has some BASIC demos, but not much more. A rarity, from start to finish.
