The Manchester University Atlas Operating System, Part I: Internal Organization by T. Kilburn, D.J. Howarth, R.B. Payne, and F.H. Sumner and Part II: Users' Description, D.J. Howarth, R.B. Payne, F.H. Sumner. Reprint of an article from The Computer Journal, October 1961.

The Atlas computer was designed and built in the Department of Computer Science at the University of Manchester with the collaboration of ICL. When it was completed, in December 1962, it was the most powerful computer in the world. It included many innovative design features of which the most important were the implementation of virtual addressing and the one-level store. This paper gives a brief summary of the structure of the Atlas and of the effect of extensive instruction overlapping on the final performance. The main part of the paper describes the implementation of the one-level store including the learning program which efficiently managed the movement of pages between the two physical levels of store.

We are extremely grateful to both Dawn and Kim Wakefield for the kind donation of the collection of their late father Richard Wakefield.