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Tediously toggling a program into the IBM 1401 mainframe

Ken Shirriff

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Beginner. No background in the topic needed.

9.1K views8 years ago1 recommendation

History and cultureHardwareRetro computingHistory of computing

Ken Shirriff demonstrates how to manually enter a prime number program into a vintage IBM 1401 mainframe using front panel switches.

Note: skip to to see the program run. I wrote a prime number program for the vintage IBM 1401 mainframe at the Computer History Museum. To make things more difficult, I entered the program using the toggle switches on the front panel, instead of reading it from punch cards. This was for the /r/retrobattlestations Flippy Switch Week: reddit.com/r/retrobattlestations/comments/8rjhl9/contest_fli…

Why it's here

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What people say. Shared to illustrate how early computers were programmed directly in machine code before compilers existed.

u/aioeuin r/C_Programming • Recommends

On “How is C created”

If you follow this back far enough, you're going to find somebody actually designed a minimal machine code monitor — in machine code itself — and physically fed that into a computer somewhere. Perhaps they used punch cards, or perhaps they toggled the program in on the computer's panel. Everything else stems from that.
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