DOS Plus
discontinued computer operating system for x86 processors
DOS Plus (erroneously also known as DOS+) was the first operating system developed by Digital Research's OEM Support Group in Newbury, Berkshire, UK, first released in 1985. DOS Plus 1.0 was based on CP/M-86 Plus combined with the PCMODE emulator from Concurrent PC DOS 4.11. While CP/M-86 Plus and Concurrent DOS 4.1 still had been developed in the United States, Concurrent PC DOS 4.11 was an internationalized and bug-fixed version brought forward by Digital Research UK. Later DOS Plus 2.x issues were based on Concurrent PC DOS 5.0 instead. In the broader picture, DOS Plus is an intermediate step between Concurrent CP/M-86 and DR-DOS.
DOS Plus is able to run programs written for either CP/M-86 or MS-DOS 2.11, and can read and write the floppy formats used by both of these systems. Up to four CP/M-86 programs can be multitasked, but only one MS-DOS program can be run at a time.
User interface
DOS Plus attempts to present the same command-line interface as MS-DOS. Like MS-DOS, it has a command-line interpreter called COMMAND.COM (alternative name DOSPLUS.COM). There is an AUTOEXEC.BAT file, but no CONFIG.SYS (except for FIDDLOAD, an extension to load some field-installable device drivers (FIDD) in some versions of DOS Plus 2.1). The major difference the user will notice is that the bottom line of the screen contains status information similar to:
DDT86 ALARM UK8 PRN=LPT1 Num 10:17:30
The left-hand side of the status bar shows running processes. The leftmost one will be visible on the screen; the others (if any) are running in the background. The right-hand side shows the keyboard layout in use (UK8 in the above example), the printer port assignment, the keyboard Caps Lock and Num Lock status, and the current time.
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This entry incorporates text from “DOS Plus” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.