In 1952 Grace Hopper developed the A-0 system, the first operational compiler: a program capable of translating instructions written in symbolic code into executable machine code. The idea seems obvious today but was radically counterintuitive to her contemporaries: Hopper had to convince her colleagues that a machine could do that translation. The compiler changes the nature of software: instead of programming directly in binary or assembly, the programmer can express intentions in a language closer to the problem. Hopper later developed FLOW-MATIC (1955) and contributed decisively to COBOL (1959), the language that would manage world finance for decades.