Here's a video of Fortran running on the IBM 1401 at the Computer History Museum: https://www.youtube.com/watch?v=uFQ3sajIdaM https://www.youtube.com/watch?v=uF

Here's a video of Fortran running on the IBM 1401 at the Computer History Museum: https://www.youtube.com/watch?v=uFQ3sajIdaM https://www.youtube.com/watch?v=uFQ3sajIdaM Because memory was so limited (8000 words), the Fortran compiler operates in 63 phases, where each phase consists of 150 to 300 instructions. In other words, the compiler's code was broken into chunks of 150-300 instructions, and that's all that could run in a phase. I'll also mention that memory was 8000 words and not 8192 words, because the IBM 1401 used decimal arithmetic.