• Amberskin@europe.pub
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    2 months ago

    Just to boast my old timer credentials.

    There is an utility program in IBM’s mainframe operating system, z/OS, that has been there since the 60s.

    It has just one assembly code instruction: a BR 14, which means basically ‘return’.

    The first version was bugged and IBM had to issue a PTF (patch) to fix it.

    • DaPorkchop_@lemmy.ml
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      2 months ago

      Okay, you can’t just drop that bombshell without elaborating. What sort of bug could exist in a program which contains a single return instruction?!?

      • Amberskin@europe.pub
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        2 months ago

        It didn’t clear the return code. In mainframe jobs, successful executions are expected to return zero (in the machine R15 register).

        So in this case fixing the bug required to add an instruction instead of removing one.