| Developer | Tony Tebby whilst working at Sinclair Research |
|---|---|
| Written in | Motorola 68000 assembly language |
| Initial release | April 1984 |
| Latest release | 1.13 |
| Available in | Spanish, French, German, Italian, Swedish |
| Platforms | Motorola 68008 |
| License | proprietary |
| Preceded by | 68K/OS |
QDOS is the multitasking operating system found on the Sinclair QL personal computer and its clones. It was designed by Tony Tebby whilst working at Sinclair Research, as an in-house alternative to 68K/OS, which was later cancelled by Sinclair, but released by original authors GST Computer Systems. Its name is not regarded as an acronym and sometimes written as Qdos in official literature.
QDOS was implemented in Motorola 68000 assembly language, and on the QL, resided in 48 KB of ROM, consisting of either three 16 KB EPROM chips or one 32 KB and one 16 KB ROM chip. These ROMs also held the SuperBASIC interpreter, an advanced variant of BASIC programming language with structured programming additions. This also acted as the QDOS command-line interpreter.[1]
Facilities provided by QDOS included management of processes (or "jobs" in QDOS terminology), memory allocation, and an extensible "redirectable I/O system", providing a generic framework for filesystems and device drivers. Very basic screen window functionality was also provided. This, and several other features, were never fully implemented in the released versions of QDOS, but were improved in later extensions to the operating system produced by Tebby's own company, QJUMP.
Rewritten, enhanced versions of QDOS were also developed, including Laurence Reeves' Minerva and Tebby's SMS2 and SMSQ/E. The last is the most modern variant and is still being improved.