Edsac read programs from a punched paper tape and printed its results. Here you can see the machine's five hole tape reader and Creed teleprinter.
A key element of Edsac's design survives in computers to this day, the practice of storing both instructions and data in memory. The stored program concept was based upon the ideas devised by the brilliant mathematician John von Neumann in 1945.
Photo credit: Computer Laboratory, University of Cambridge