In the algorithm, mod stands for modulus, that is, remainder. Modular operation, that is, remainder operation, is an operation to find the remainder of one integer x divided by another integer y in integer operation, regardless of the quotient of the operation. In the algorithm, mod stands for modulus, that is, remainder. Modular operation, that is, remainder operation, is an operation to find the remainder of one integer x divided by another integer y in integer operation, regardless of the quotient of the operation.