C H Devonald’s early suggestion for an instruction set for the Ferranti FPC/1 computer, later named Pegasus.

Internal memo from C H Devonald (Ferranti’s London Computer Lab) to John Bennett, though ‘Bennett’ has been scored through and replaced by ‘Braunholtz’. Two foolscap hand-written sheets, together with a green Internal Memo address slip. Summary and comment: W S Elliott (leading the London group) is asking John Bennett to have a look at Devonald’s suggested instruction set for the proposed FPC/1 (Ferranti Packaged Computer) which was later re-named Pegasus. Devonald is suggesting 6 function digits plus 6 address digits per instruction and three instructions packed into a (36-bit) word. This is very different from the final Pegasus architecture, which was strongly influenced by Christopher Strachey.