The Wash$-$O$-$Ma$$c Laundromat is a computerized laundry reserva$$on system. As each

customer enters, he or she puts coins into slots at one of two sta$$ons and types in the

number of washing machines he$/$she will need. The sta$$ons are connected to a central

computer that automa$$cally assigns available machines and outputs tokens that

iden$$fy the machines to be used. The customer puts laundry into the machines and

inserts each token into the machine indicated on the token. When a machine finishes

its cycle, it informs the computer that it is available again. The computer maintains an

array available$[$NMACHINES$]$ whose elements are non$-$zero if the corresponding

machine is available,NMACHINES is a constant equal to the number of machines there

are in the Laundromat, and free is a semaphore that indicates the number of available

machines.

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