1．采用位触发方式编写程序，使计算机发出音响并演奏乐曲（例如《两只老虎》等）。

进一步理解程序直接控制I/O方式和位触发方式控制声音的工作原理。

一首乐曲是由不同频率和节拍的音调组成，因此控制脉冲的频率和持续时间是编写乐曲程序的关键。根据已知的音符频率对照表，设置乐曲的频率表和节拍时间表；

编写程序并调试通过。

2．了解定时器的工作原理，掌握利用定时器产生声音的方法，使计算机演奏乐曲（例如《两只老虎》等）。编写程序并调试通过。-1. Write programs using digital trigger, so that the computer and playing audible music (such as " Two Tigers" , etc.). Further understanding of the direct control program I/O mode and trigger control bit sound works. A piece of music is the beat of different tone frequencies and the composition, thereby controlling the frequency and duration of pulse is the key to writing music program. Note the frequency according to the known table, set the music and the beat frequency table timetable　programming and debugging through. 2. Understand the working principle of the timer, the timer produces sound control methods used to make the computer play music (such as " Two Tigers" , etc.). Programming and debugging through.