Operating systems › DOS (MS-DOS / DR-DOS) › MS-DOS 1.0

MS-DOS 1.0

1981

Microsoft's 1981 operating system for the original IBM PC, a single-tasking command-line system derived from 86-DOS.

Machines

IBM PC 5150

IBM PC/AT

IBM PC/XT

IBM PCjr

Chips

IBM CGA

IBM EGA

IBM MDA

IBM PC speaker

Intel 80286

Intel 8088

Motorola MC146818 RTC

TI SN76489

Reference & documentation

External technical references for programming MS-DOS 1.0 and for writing emulators.

ResourceTypeNotes
EXE Format - ModdingWiki ↗FormatMZ EXE header, relocation table field-by-field
Design of the FAT file system ↗FormatHex-offset tables for FAT12/16 structures
Ralf Brown's Interrupt List (master files) ↗Interrupt listAuthor's canonical release downloads
HelpPC: INT 21h DOS Function Dispatcher ↗Interrupt listEvery INT 21h function with registers and returns
MS-DOS Encyclopedia: PSP Structure ↗Memory mapOfficial 256-byte Program Segment Prefix layout diagram
HelpPC: Program Segment Prefix layout ↗Memory mapPSP field offsets 00h through 81h
WinWorld: MS-DOS 1.x disk images ↗ROMsDownloadable bootable MS-DOS 1.x OEM floppy images
microsoft/MS-DOS compiled binaries ↗ROMsOfficial compiled MS-DOS 1.25 binaries alongside source
MS-DOS Programmer's Reference (INT 21h) ↗ReferenceOfficial function request service reference, calling conventions
Microsoft MS-DOS Source Code ↗SourceOfficial asm sources for v1.25, 2.0, 4.0
mist64/msdos1 - annotated DOS 1.0 disassembly ↗SourceReassemblable boot sector, IBMBIO, IBMDOS disassembly