MS-DOS 1.x

Originally 86-DOS, written by Tim Paterson of Seattle Computer Products, DOS was a rough clone of CP/M for 8086 based hardware. Microsoft purchased it and licensed it to IBM for use with Microsoft's IBM PC language products. In 1982, Microsoft began licensing DOS to other OEMs that ported it to their custom x86 hardware and IBM PC clones.

For IBM-specific releases, please see the IBM PC-DOS product page.

DOS 1.x was very limited in what it could do. It could start applications (.COM and .EXE), and process batch files (.BAT). DOS 1.0 worked with 160KB floppies and did not support folders (all files had to be in the root). The command interpertor supported the following commands:


No pipes, redirection, or device drivers were supported. The DOS API in 1.0 was very limited.

MS-DOS 1.25, the equivalent of PC-DOS 1.10, was the first version licensed to OEMs beyond IBM or Seattle Computer Products.

Some vendors labeled their versions of MS-DOS with different names and version numbers. All of the versions here are believed to be based off of MS-DOS 1.25, even if the vendor called it something else.

Installation instructions

Important: Many of these OEM versions will only run on the specific computers they were designed for. Others may boot on an IBM PC, but certain devices or tools may not operate. Some require special disk formats or drive hardware, such as 8" floppy drives.

Most of these images need to be written with ImageDisk, or some other DOS based disk writer. WinImage can not handle the file system on most DOS 1.x disks.

Those that are compatible with the IBM PC (Such as the Columbia Data Products OEM) can be mounted and booted in an emulator such as MESS or PCE.

Please see the documentation included with each for specifics.

Wanted: Eagle 1600 MS-DOS 1.25 with hard disk diag disk.

Product type
Release date
Minimum CPU
Intel 8088 4.77MHz
Minimum RAM
Minimum free disk space
User interface


Download Name Version Language CPU File type File size
MS-DOS 1.25 (Z-DOS) (5-27-1983) [Zenith Z-100] (5.25-320kb) 1.25 (Z-DOS) (5-27-1983) [Zenith Z-100] English x86 5¼ Floppy 371.87KB
MS-DOS 1.25 (Z-DOS) (8-11-1983) [Zenith Z-100] (5.25-320kb) 1.25 (Z-DOS) (8-11-1983) [Zenith Z-100] English x86 5¼ Floppy 419.81KB
MS-DOS 1.25 [CDP OEM R2.11] (5.25-320k) 1.25 [CDP OEM R2.11] English x86 5¼ Floppy 399.9KB
MS-DOS 1.25 [CDP OEM R2.11] Manual 1.25 [CDP OEM R2.11] English x86 Archive 25.56MB
MS-DOS 1.25 [Compaq OEM r1.10 Rev B] (5.25-320k) 1.25 [Compaq OEM r1.10 Rev B] English x86 5¼ Floppy 567.02KB
MS-DOS 1.25 [Compaq OEM r1.10] Manuals (Dec 1982) 1.25 [Compaq OEM r1.10] English x86 Archive 177.02MB
MS-DOS 1.25 [Compaq OEM r1.11] (5.25-320k) 1.25 [Compaq OEM r1.11] English x86 5¼ Floppy 1.33MB
MS-DOS 1.25 [Compaq OEM r1.12] (5.25-320k) 1.25 [Compaq OEM r1.12] English x86 5¼ Floppy 247.58KB
MS-DOS 1.25 [Compaq OEM r1.1x] Manual 1.25 [Compaq OEM r1.1x] English x86 Archive 31.47MB
MS-DOS 1.25 [Corona Data Systems OEM (BIOS 1.03)] (5.25-320k) 1.25 [Corona OEM (BIOS 1.03)] English x86 5¼ Floppy 67.35KB
MS-DOS 1.25 [Corona Data Systems OEM (BIOS 1.07)] (5.25-320k) 1.25 [Corona OEM (BIOS 1.07)] English x86 5¼ Floppy 132.82KB
MS-DOS 1.25 [Hyperion] (5.25-320k) 1.25 [Hyperion] English x86 5¼ Floppy 338.53KB
MS-DOS 1.25 [Micromint MPX-16] (5.25-160k) 1.25 [Micromint MPX-16] English x86 5¼ Floppy 129.46KB
MS-DOS 1.25 [SCP OEM] [SCP Cromemco S-100] (8-inch DSDD) 1.25 [SCP OEM][SCP Cromemco S-100] English x86 Archive 435.34KB
MS-DOS 1.25 [SCP OEM] [SCP Tarbell S-100] (8-inch SSSD) 1.25 [SCP OEM] [SCP Tarbell S-100] English x86 Archive 308.68KB
MS-DOS 1.25 [Sanyo MBC-550 OEM r1.00] (5.25-160k) 1.25 [Sanyo MBC-550 OEM r1.00] English x86 5¼ Floppy 112.21KB
MS-DOS 1.25 [TI Professional Computer OEM r1.13] (5.25-320k) 1.25 [TI Professional Computer OEM r1.13 English x86 5¼ Floppy 206.99KB
MS-DOS 1.25 [TI Professional Computer OEM r1.13] Manual 1.25 [TI Professional Computer OEM r1.13 English x86 Archive 36.07MB
MS-DOS 1.25 [Zenith Z-100 PC] (5.25-320kb) 1.25 [Zenith Z-100 PC] English x86 5¼ Floppy 62.72KB
MS-DOS 1.25 for Commodore CBM B Series 1.25 for Commodore CBM B Series English x86 Archive 90.65KB


Comments by