Lacking a mention of: https://www.ece.cmu.edu/~ganger/712.fall02/papers/p761-thompson.pdf https://www.ece.cmu.edu/~ganger/712.fall02/papers/p761-thomp... And o

Lacking a mention of: https://www.ece.cmu.edu/~ganger/712.fall02/papers/p761-thompson.pdf https://www.ece.cmu.edu/~ganger/712.fall02/papers/p761-thomp... And of the IBM 1401: http://en.wikipedia.org/wiki/IBM_1401 http://en.wikipedia.org/wiki/IBM_1401 The later is relevant, since as you can see from the opcode description on the wikipedia page, the "source code" of an (assembler) program, as characters punched on a card, had the exact binary representation of the machine code executed by the computer. In effect, the source code was directly interpreted by the hardware. Even if this source code being machine code was not close to English like Cobol sources, or to Mathematics like Fortran sources, it was still source code. Hence the answer to the question: source code was there before the compiler (beside, before compilers were assemblers and autocoders, that had also source codes).