A byte is 8 bits, and an int is 16 bits. When converting int to byte, the first (left) 8 bits are discarded, leaving the last 8 bits.

88+68=156, converted to int type binary is 0000000010011100, and then converted to byte is 10011100. Because the highest bit is the sign bit, which is the bit that indicates positive and negative, so 1 here represents a negative number, and the rest is as follows The conversion of the original code and complement code rules is 100, so it is -100