假设系统中有n个进程共享3台扫描仪，并采用PV操作实现进程同步与互斥。若系统信号量S的当前值为-1，进程P1、P2又分别执行了1次P（S）操作，那么信号量S的值应为（ ）。
- A.3
- B.-3
- C.1
- D.-1
正确答案及解析
正确答案
解析
当有进程运行时，其他进程访问信号量，信号量就会减1。S=-1-2。
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