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A Universal Turing Machine In 100 Punchcards

Posted by timothy on from the animation-to-blow-your-mind dept.

New submitter theclockworkcomputer writes "100 years ago tomorrow, Alan Turing was born. To celebrate, I wrote a Universal Turing Machine in 100 Punchcards. I've uploaded a video to explain a small part of the read head (the Jacquard). One needle is shown out of a total of 28. As this is about a program for a Turing Machine and not about a Turing Machine itself, I hope to be excused from the requirement of infinite tape."

2 of 48 comments (clear)

  1. Wow you couldn't even read the summary? by Anonymous Coward · · Score: 4, Informative

    This is not a universal Turing machine, since those things are impossible in this universe. Not even humans are universal Turing machines.

    Right. And from excessively short summary:

    As this is about a program for a Turing Machine and not about a Turing Machine itself, I hope to be excused from the requirement of infinite tape.

  2. Re:Just to be pedantic by tendays · · Score: 5, Informative

    Indeed. Turing machines don't require infinite tapes, they require unbounded tapes. In particular the initial state of the tape must contain at most a finite number of non-blank cells. Working with a finite tape is therefore fine as long as you are ready to enlarge it when the head reaches the boundary (so that, to the machine, it appears infinite). In the same sense, a physical computer could act as a Turing machine if, when it runs out of memory, an operator could come and plug in an extra hard drive (and if memory addresses were made in a way that they can be arbitrarily large).