MOS versions

OS 1.10

Existence implied by existence of OS 1.20. Reported to exist by arg, immediately before 1.20: Acorn sent Hitachi editing instructions to derive 1.20 from 1.10 by telex, as the two differ only in patches.

OS 1.20

Standard production MOS for BBC A/B.

OS A1.0

American OS 1.20

OS 1.21

Existence implied by existance of OS 1.23.

OS 1.22

Existence implied by existance of OS 1.23.

OS 2.00

Standard production MOS for BBC B+.

OS 2.10

Cambridge Workstation

OS 2.30

Standard production MOS for Reuters BBC B+. "OS R0.3"

MOS 3.00

Existence implied by existance of MOS 3.20.

MOS 3.10

Existence implied by existance of MOS 3.20.

MOS 3.20

Standard production MOS for BBC Master.

MOS 3.21

Bugfixes to MOS 3.20 for BBC Master.

MOS 3.30

Existence implied by existance of MOS 3.50.

MOS 3.40

Existence implied by existance of MOS 3.50.

MOS 3.50

Optional upgrade for BBC Master.

MOS 3.51

Bugfixes to MOS 3.50 for BBC Master.

MOS 3.5A

Tinsley

MOS 4.00

Standard production MOS for BBC Master ET.

MOS 5.00

Early production MOS for Master Compact.

MOS 5.10

Standard production MOS for Master Compact.

MOS 5.11

Production MOS for Master Compact.