Converter code (ENIAC)
The 1948 conversion that made ENIAC six times slower and considerably more useful, by moving the program out of the cables and onto a wall of switches.
After the Moore School lectures everybody wanted a stored program, but ENIAC was already installed at Aberdeen and was not going to be scrapped. Richard Clippinger at the Army's ballistics laboratory proposed a shortcut: the machine's three function tables were in effect a read-only memory of several thousand digits, meant for lookup values. Put orders there instead, wire in a fixed instruction set to interpret them once and for all, and the function tables become a program store. John von Neumann and Adele Goldstine worked out the design, and the machine ran in the new mode from September 1948.
The price was brutal. Every order now had to be decoded by the machine itself rather than sitting pre-wired in patch cords, and ENIAC gave up roughly five-sixths of its speed. The gain was larger: a new problem went from days of recabling to hours of setting switches, and could be written down and kept. Useful output rose so sharply that the machine survived until 1955 — an unusually clean demonstration that architecture beats clock rate.