输入为8421BCD码，输出为8421BCD码。

程序中自动对输入进行转换，将8421BCD转换成余3码，然后采用修正函数实现加法，并且利用程序将加法结果转换成8421BCD码进行输出，且输出转换前后的中间结果。

-8421BCD code input and output for 8421BCD yards. Procedures for automatic input conversion, will be converted into 8421BCD I 3 yards, and then use that function to achieve additive, the use of procedures and the results will be converted into Adder 8421BCD codes for output and the output before and after conversion of the intermediate results.