MS-DOS 1.25

MS-DOS 1.25
	Version of MS-DOS
Version	1.25
Release date	1982-04
Replaces
	MS-DOS 1.24
Replaced by
	MS-DOS 1.26

MS-DOS 1.25 was released in April 1982 as the first general release to OEM customers other than IBM, so it was used by all the first clone manufacturers. Some OEMs labeled their release with different version numbers (e.g. COMPAQ), but they are all based on version 1.25.^[1]

It supported both single sided (160KB) and double sided (320KB) 5.25" floppies and there was no sub-directory support (all files must be located in the root directory). As a result of that, \, / and other symbols can be used in file names.

Versioning[edit | edit source]

The DOS kernel always reports version 1.25. COMMAND.COM from the original (1982-03) compile reports version 1.17 and COMMAND.COM from the updated (1982-08) release reports 1.18.

An extra H can be seen at the end of the version string for some OEM releases, and it means the OS was assembled with the HIGHMEM switch enabled, which causes DOS to be loaded to the highest blocks of memory.

Changes from MS-DOS 1.24[edit | edit source]

MS-DOS 1.24 corresponds to IBM PC-DOS 1.10^[1] and there is only one minor change between the two versions as described by the writer of DOS, Tim Paterson.^[1] The change was a marker (00) being placed at end of the directory to speed up searches.

Internal commands[edit | edit source]

The Command Interpreter, COMMAND.COM, supports these commands:

DIR
TYPE
COPY
ERASE
RENAME
PAUSE
REM

Bugs and quirks[edit | edit source]

The SYS utility can only transfer the system if the destination disk is already a system disk, which means it cannot transfer the system to a blank/empty disk. This bug was fixed by Tim Paterson after he left Microsoft and returned to Seattle Computer Products, and therefore SCP was the only OEM to have this bug patched.^[2]