When assigning values to variables, they are all in binary form. If it exceeds its maximum value, it will cut off more digits than it does, leaving a low bit, assuming that an unsigned char a； is defined; 8-bit binary, if it is equal to a = 257.

The binary of 257 is 1000 000 1, so he will remove the highest bit of 1, leaving 00 000 1, and the final result is A = 000000 1 B, which is a =/kloc-0. Other types of principles. I wish you progress.