Diff — 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 report|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]]

[[Category:History]]

[[Category:Hardware]]