Wednesday, February 17, 2010

Paper Tape

When there was a mistake in a long CNC program, sometimes it was easy to tell that it was a mistake at the beginning of the program. Rather than read the whole thing in, edit it in WordStar and then punch a whole new tape, sometimes it was easier to repair the paper tape itself.

Usually you could just create a new section of paper tape, and then you unroll the tape to the section you are looking for and splice in the change. With some practice it wasn't too hard to read the binary numbers by eye. Instead of ASCII values, CNC programs were punched to tape using EIA (Electronic Industries Association) codes.

In some instances if you didn't need to change the number of characters, but just which values (change some digits for example), you could just cover the holes with tape and punch new holes. I think I did that at least a couple of times.

So, this all seems very archaic right? On the plus side you really had control over the stored data. Today if your disk drive or your flash memory loses a bit you can't even see it let alone fix it. ;-)

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