PC DOS 1.0

1981 · DOS

Microsoft made it for the IBM PC from 86-DOS. It was shipped when IBM first released the PC, in August 1981.^{1, 2}

Announced: 12 August 1981, with the IBM PC^{1, 3}
Made by: Microsoft, for IBM^{1, 2}
Based on: 86-DOS, by Tim Paterson²
Came on: One 160 KB floppy disk³

Why it was made

IBM was building its Personal Computer and needed an operating system for it. Microsoft was already writing BASIC for the new PC, so IBM asked it for the operating system too.² Microsoft licensed 86-DOS, which Tim Paterson had written at Seattle Computer Products, and later bought all the rights to it.²

Close-up of green text on a black screen: 'Enter today's date (m-d-y): 8-12-81', then 'The IBM Personal Computer DOS' and 'Version 1.00 (C)Copyright IBM Corp 1981', then the A> prompt with the command 'dir *.com' and the first files of a list. — Illustration · not a screenshot Close-up of our drawing: after asking for the date, PC DOS 1.0 introduces itself as “The IBM Personal Computer DOS”. See the real screen

What it looked like

You worked by typing commands at the A> prompt, such as DIR to list the files on a disk.^{2, 3} PC DOS 1.0 could only use floppy disks.² Its one disk also held the BASIC language and 23 example programs written in it.³

Green text on a black screen: a date prompt, the PC DOS 1.0 start-up message, the command 'dir *.com', a list of 14 programs from COMMAND COM to BASICA COM with their sizes and the date 08-04-81, and the A> prompt with the cursor. — Illustration · not a screenshot Our drawing of PC DOS 1.0 on IBM's monochrome display: the start-up message, then DIR listing the programs on the disk. See the real screen

Key moments

1980 In July, IBM approaches Microsoft about a project code-named "Chess".⁴ In December, Microsoft licenses 86-DOS for $25,000.²
1981 On 12 August, IBM unveils the IBM PC in New York. PC DOS 1.0 launches alongside it.^{1, 2}
2014 With Microsoft's permission, the Computer History Museum publishes the source code of MS-DOS 1.1 and 2.0.²
2018 Microsoft puts the source code of MS-DOS 1.25 and 2.0 on GitHub.⁵
2024 Microsoft, working with IBM, releases the source code of MS-DOS 4.00 under the MIT license.⁶