These observations are prompted by the mystical feelings I have for this computer, which was the first one I saw on coming out of the egg in 1961, age 28.
Given the Pegasus as a sacred object, its bible is surely George Felton's Programming manual,
published, late in its life, in 1962. It is available
here as a 32Mb pdf.
(If you'd like your own copy, use the Acrobat "Save a copy"). If you haven't
the patience for the whole thing, the order code is on pages
271,
272,
273, and
274.
If the page looks too small to read, you may have the
(default) Internet Explorer
setting that shrinks images to fit the screen. If you wait, with the mouse
on the page,
eventually a sort of beetle icon appears at the bottom right which you can click to get
back to the foolscap page. If you have Firefox, you can just click on the screen to
make it big or small - or use Control-Plus and Control-Minus.
George's manual is not a work for the faint-hearted dilettante, it is a beautifully written clear exposition of exactly what programming the Pegasus means.
I say 'means' rather than 'meant', because you can run a Pegasus emulator on your PC. It's not quite the same as approaching the mighty creature with trembling hands, a dodgy programme on paper tape, and the hope to use your ten minutes well. Imagine, doing Start and Run, and seeing your tape run from the perspex container into the bin. That may be possible for some of us on the restored machine at the Science Museum.
But for now, all praise to Chris Burton and Manchester University for making the emulator available. I met Chris briefly at ICL, through my friend Dave Emmett - they had both worked on the 1900 OS 'George 3' (supposedly named for the GF above), but I never knew Chris was a Pegasus junkie. The Computer Conservation Society cherishes the Pegasus, and one relevant page, with links to their magazine 'Resurrection', is here.
Here is a link to what looks like a thorough survey of computing in the 50s.
And here is a description (perfectly genuine, Reader, I assure you) of the Pegasus delay line in German:
