生產者-消費者

var buffer: array[0,..., n -1] of item;

empty, full mutex : semaphore := n, 0, 1;
in, out : integer := 0, 0;

codebegin
    process Pi
    begin
        生產產品;
        P(empty);
        P(mutex);
        往buffer[in]放產品
        in := (in + 1) % n;
        V(mutex)
        V(full);
    end

    process Ci
    begin
      P(full);
      P(mutex);
      從buffer[out]取產品
      out := (out + 1)mod n;
      V(mutex);
      V(empty);
      消費產品
    end
codeend