Source Code as History

When the history of early software development is written it will be a travesty. Few historians will have the ability, and even fewer the inclination, to learn long dead programming languages. History will be derived from the documentation not the source code. Alan Turings perplexed, hand written annotation “How did this happen?” on a cutting of Autocode taped into his note book will remain a mystery.

How did this happen? Annotation of a program bug by Alan Turing

What kind of bug would stump Alan Turing? Was it merely a typo that took a few hours to find? a simple mistake maybe? Or did the discipline of the machine expose a fundamental misconception and thereby teach him a lesson? The only way to know would be to learn Autocode.

Page from Alan Turing's notebook showing an annotated program with a bug

The first stored program to be successfully executed was written by Tom Kilburn and executed on Monday 21 st June 1948 at Manchester University, England. It is said that this was the first and last program that Kilburn ever wrote. The program found the highest factor of a number and took 1 minute to complete on it’s first run. A second run with a different number took 2 minutes and 52 seconds. Unfortunately no one thought to document the program until Geoffrey C. Tootill wrote an amended version in his note book a month later on the 18 th July 1948. The original has been lost. Below is a copy of Tootill’s version.

Page from Geoffrey C. Tootill's notebook showing his amended version of the first, successfully executed, stored program

Via The National Archive for the History of Computing

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