.采用原理图输入法和文本输入法实现全减器，分层设计，底层由半加器（也用原理图输入法）和逻辑门组成；

2.给出此项设计的仿真波形；

3.选择实验电路进行验证, 由发光管指示显示结果。

-. The use of schematic and text input method input method to achieve full subtracter, hierarchical design, the bottom of the half adder (also used schematic entry method), and logic gates　2 shows the design of the simulation waveform　3. Select the experimental circuit to verify the result by the LED indicator is displayed.