The world's first programme stored and run on a computer
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The first programme to be stored in a computer was written by Tom Kilburn, and run for the first time on the 21st June 1948, on Manchester Mark 1, the world's first stored-program computer. It was a program to find the highest proper factor of 2^18, this was to be done by trying in a single routine every integer from (2^18-1) downward, the necessary divisions were done not by long division but by repeated subtraction of the divisor (because the Mark 1 only had a hardware subtractor). About 130,000 numbers were tested, this involved 3.5 million operations. The correct answer was obtained in a 52-minute run. The program was encoded in only 17 instructions
The original program has been lost. The revised version (below)
is from G.C. Tootills notebook, a contemporary of Kilburn. This
uses two extra instructions to copy the trial factor because the
original version overwrote it with the final answer, resulting in
the need for it to be keyed in again before the program could be
rerun. In this version C is used to represent the computer (ie
accumulator), Cl to represent control register, the other letters
a,b,r are respectively the number for factorizing, a trial factor
and a remainder.
~ o ~
A Simulator of Mark 1
including binary code of the first programme is available.