In C language, the operand must be an integer, the operator is%, and the modular operation is to take the remainder in mathematics. The operation must require an integer operand.

The specific reasons are:

1, the remainder operation must be an integer, because the remainder is an operation in integer division. The remainder refers to the undivided part of the dividend in integer division. For example, if 23 is divided by 5, the quotient is 4 and the remainder is 3.

2. Bit operations must be integers, because bit operations are operations on bits in integers. As shown in the figure: