Short Code

John Mauchly proposed in 1949 a notation in which mathematical expressions are written roughly as they appear in a textbook and then represented as pairs of characters that the machine interprets at run time. William Schmitt implemented it on BINAC that same year and rebuilt it for the UNIVAC I in 1950. One word held six operations of two characters each — 07 for plus, 03 for the equals sign, and onward through a table covering the common functions. Square root and absolute value became codes rather than subroutines you wrote yourself.

It was not a compiler, and the distinction matters. The programmer still translated the formula into number pairs by hand, table at their elbow; the machine ran an interpreter that decoded the pairs one at a time during execution. The cost was roughly fifty times slower than hand-written machine code, which was a lot to ask of an institution that had paid a million dollars for the UNIVAC.

Even so, Short Code is the first notation above machine code that actually ran on a computer. Plankalkül was both earlier and considerably more sophisticated but sat unpublished in a drawer until 1972. The next step was Grace Hopper's A-0 in 1952, which automated the translation itself — and which is therefore usually counted as the first compiler.