The Read Semaphore Values routine returns the current or maximum
    values, or both, of the specified counting semaphore. The
    semaphore must have been created by PPL$CREATE_SEMAPHORE.

    Format

      PPL$READ_SEMAPHORE  semaphore-id [,semaphore-value]

                          [,semaphore-maximum]

1  –  Arguments

 semaphore-id

    OpenVMS usage identifier
    type          longword (unsigned)
    access        read only
    mechanism     by reference
    Identifier of the specified semaphore. The semaphore-id argument
    is the address of an unsigned longword containing the identifier.

    Semaphore-id is returned by PPL$CREATE_SEMAPHORE.

 semaphore-value

    OpenVMS usage word_signed
    type          word (signed)
    access        write only
    mechanism     by reference
    Receives information about the specified semaphore. The optional
    semaphore-value argument is the address of a signed word
    containing the current value of the semaphore or the number of
    blocked processes. If positive, semaphore-value contains the
    number of available resources associated with this semaphore;
    if negative, it contains the number of waiting processes. If the
    value returned is zero, there are no available resources and no
    waiting processes.

 semaphore-maximum

    OpenVMS usage word_signed
    type          word (signed)
    access        write only
    mechanism     by reference
    Maximum value of the semaphore. The semaphore-maximum argument is
    the address of a signed word containing the maximum value of the
    semaphore specified by semaphore-id.