Impressions of the early days of programming

The paper describes the author's experience of working with the Edsac, Cambridge, England, in 1951 and 1953. The author's background in astronomical calculations using hand methods and his plans for spending a year in Cambridge are first described. This is followed by impressions of the Mathematical Laboratory, Cambridge, its staff, the external characteristics of the Edsac, the library of subroutines, documentation for programmers, machine language, paper tape preparation equipment, and organization of the use of the Edsac. The second major part of the paper describes the steps leading to an Edsac-program for calculating the motion of a minor planet by step-by-step integration of the equations of motion, with special attention to the preparation and check of large amounts of input to the program.