Manchester Mark 1

Manchester Mark 1

The Manchester Mark 1 was the computer the Baby grew into — and the prototype every commercial computer descends from. Frederic Williams, Tom Kilburn, and Geoff Tootill built it at Victoria University of Manchester from August 1948, scaling their June-1948 Baby into a real machine: index registers (the famous "B-lines"), a magnetic drum backing store, and an instruction set a human could work with. The first version ran by April 1949; on the night of 16/17 June 1949 a Mersenne-prime search ran nine hours without error — the first long computation in history.^[1]

The B-lines deserve their own sentence: the Mark 1 was the first computer with index registers, letting a program modify its own addresses to walk through an array — the ancestor of every array loop ever written. Thirty-four patents came out of the project, and its ideas surfaced in the IBM 701 and 702 as well as its own commercial descendant.^[2]

"Electronic brain" — and the birth of the debate

The British press covered the Mark 1 as an "electronic brain" — and the phrase provoked the first recorded backlash in AI's long history: the head of Manchester's neurosurgery department objected publicly, opening a debate about whether a computer could ever be truly creative that has not yet ended. The government was quicker to act: Chief Scientist Ben Lockspeiser saw the machine in October 1948 and immediately contracted Ferranti to build a commercial version — the letter authorized them "to construct an electronic calculating machine to the instructions of Professor F. C. Williams."^[3]

Where the software era started

The Mark 1's software history may outshine its hardware. Alan Turing joined Manchester in 1948 and wrote the machine's input routines and much of its programming manual — the Programmers' Handbook is largely his. And on this machine's legendarily abstruse machine code — teleprinter-coded instructions with the bits backwards — Alick Glennie built the first working Autocode in 1952, arguably the first compiled language ever run. The first modern machine also hosted the first attempt to make programming less miserable.^[4] article — Turing's input routines/manual and Glennie's 1952 Autocode]]

Where it sits

The Mark 1 lived one and a half years and its offspring are still shipping. Between the Baby's proof-of-concept and the Ferranti's product line, it is the hinge machine of the stored-program era — the first computer with index registers, Turing's professional home, and the machine whose users immediately invented high-level programming to escape it.

Check your understanding

• What memory technology did the Mark 1 inherit from the Baby?
• What architectural feature — a first — did the Mark 1 introduce for array handling?
• What did Turing contribute to the Mark 1?
• What did the Mark 1 become commercially, and why is that machine first-of-kind?