Last Updated on: 7th May 2025, 10:46 am
Web site: www.digitalresearch.biz
Origin: USA
Category: Others
Desktop environment: CLI
Architecture: Intel 8086/80186
Based on: CP/M
Wikipedia: DOS Plus
Media: Install
The last version | Released: 2.1 | unknown
DOS Plus (also called DOS+) – a disk operating system developed by Digital Research and released in 1985. It can be seen as an intermediate stage between CP/M-86 and DR-DOS.
It can run programs written for both the CP/M-86 and MS-DOS 2.11 environments, and can read and write to the floppy disk formats used by both systems. It is capable of multitasking (up to four CP/M-86 programs), but can only run one DOS program at a time.
DOS Plus is initialized by a single file called DOSPLUS.SYS (instead of the MS-DOS combination IO.SYS / MSDOS.SYS). This file is in CP/M-86 CMD format, and is internally structured as a set of modules:
The BDOS kernel, which handles multitasking and implements the CP/M API.
XIOS, which is the machine-dependent component, which performs low-level disk and character I/O functions.
The DOS emulator, which converts each MS-DOS function call into one or more CP/M calls. In the case of a directory change request, for example, this would be translated as a series of ‘open directory’ calls, one for each directory in the search path.
A module that loads COMMAND.COM when needed. This module contains the string “OS=CPCDOS”, suggesting that it is based on Concurrent DOS code.
DOS Plus was the main operating system on non-IBM PC compatible computers such as the BBC Master 512 and the Philips :YES. PC compatible versions were supplied with the Amstrad PC1512 and the TRAN Jasmin Turbo.
