EDSAC

EDSAC — the Electronic Delay Storage Automatic Calculator — was the computer built by Maurice Wilkes at the University of Cambridge that ran its first programs in May 1949. It was not the first stored-program machine to switch on — the Manchester Baby beat it by eleven months — but it was the first to run a useful computing service: real users submitting real problems and getting real answers.

Origin

Wilkes visited the United States in 1946, saw the ENIAC work and attended the Moore School lectures on electronic computer design — where the EDVAC ideas were presented. He came back to Cambridge determined to build a practical machine. EDSAC was designed in early 1947 and, unlike the Baby, built for daily use from the start: 3,000 vacuum tubes, mercury delay-line memory, paper tape input, teleprinter output.

The machine ran its first program — a routine to print a table of squares — on 6 May 1949. By the end of the month it was doing regular work for Cambridge's mathematics and physics groups.

Why it matters more than the race

The Baby was a proof-of-concept; EDSAC was a computer. What Wilkes's team built on top of the hardware became the foundation of programming practice:

• A subroutine library — EDSAC's programmers wrote reusable punched-tape routines (sine, square root, division…) and kept them in a cabinet; users copied them into their programs. The first software library — and the first place the word "library" means code.
• Assembler-style notation — Wilkes's team wrote programs in a mnemonic "initial orders" notation that was translated by the machine, the earliest working assembly system.
• The first software book — Wilkes, Wheeler, and Gill's Preparation of Programs for an Electronic Digital Computer (1951) — the first textbook on programming, for decades just called "Wilkes, Wheeler, and Gill."
• Debugging in the wild — Wilkes famously wrote: "the realisation came over me with full force that a good part of the remainder of my life was going to be spent in finding errors in my own programs." The first programmer to discover debugging was real.

Legacy

• EDSAC 2 followed in 1958; Wilkes built microprogramming (the idea that a CPU's control logic is itself a program) into it — a design technique still at the heart of processors.
• Cambridge's computing culture fed directly into the British software industry: EDSAC alumni founded or seeded companies and labs across the country.
• Wilkes won the Turing Award in 1967, the second ever given.

See also

• Manchester Baby
• EDVAC report
• John von Neumann
• The first programmers
• History of Programming

References

1. Lavington, Simon. Early British Computers (Manchester UP, 1980).
2. Wilkes, Maurice V. Memoirs of a Computer Pioneer (MIT Press, 1985).
3. Lavington, Simon. A History of Manchester Computers (NCC Publications, 1975; 2nd ed. 1998).