Sinclair QDOS
Sinclair QDOS was the multitasking operating system found on the Sinclair QL and its clones.
Rewritten, enhanced versions exist in the form of Minerva, SMS2 and SMSQ/E. The latter is the most modern variant and is still being improved.
Originally written for the Motorola 68000 CPU, with a 48KB ROM for a computer with only 128KB RAM.
Sinclair QDOS included the SuperBasic interpreter, a well designed variant of BASIC with structured programming additions.