Question

A textbook titled for these things uses them to solve “not-so-classical problems” like the baboon crossing problem and “not remotely classical problems” like the sushi bar problem. That book, written by Allen Downey, is called “The Little Book of” these things. David Parnas found a flaw in Suhas Patil’s proof that these things aren’t powerful enough to solve the cigarette smokers problem. (15[1])Two of these things keep track of the number of items and empty spaces in a buffer in the classic solution (-5[1])to the (*) producer-consumer problem. (10[1])This data type supports two operations, historically named V (10[1])and P from the initials of Dutch words. (10[2]-5[1])Some English texts name those two operations “vacate” and “procure” to match the initials, while others call them “up” and “down”, or “signal” and “wait”. For 10 points, name this concurrency primitive invented by Edsger Dijkstra (10[1])that holds a nonnegative integer, whose name comes from telegraphy. ■END■ (10[2]0[1])

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