模拟PV操作同步机构，从键盘上输入一组字符，由生产者每次读入一个字符供消费者输出。运行模拟程序，打印依次读入的字符和经消费者输出的字符。-PV operation synchronization, analog, keyboard input from a group of characters, from the producer read a character for each consumer output. Run the simulation program, print the c