Tony Harminc wrote: > Do you mean an algorithm? ... I'm not sure there is an overall > algorithm, though obviously there are certain patterns to be > seen.
Of course there is an algorithm. Card readers implement it. In fact, it can be deduced (or reverse engineered) simply by use of Boolean algebra. It was one of the first assignments given by Fred Brooks in his graduate computer architecture course. The goal, of course, was to (painfully) lay out the de facto logic that transformed the binary card row values (given on the green card) to yield the corresponding S/360 byte values, then reduce all that to the simplest possible circuit using Boolean algebra. The simplest implementation in the class was about 70 Sheffer strokes, although Dr. Brooks said that the (even then-old) 2540 did it with a much simpler circuit (if one ignored the parity bit that got generated, and all the internal self-checking logic, which was critical, and all of the extra logic to detect invalid hole punch combinations). -- WB ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
