Modulo Operator (%) in C/C++ with Examples

The modulo operator, denoted by %, is an arithmetic operator. The modulo division operator produces the remainder of an integer division which is also called the modulus of the operation.

Syntax of Modulus Operator

If x and y are integers, then the expression:

x % y;

Return Value of Modulus Operator

If y completely divides x, the result of the expression is 0.
If x is not completely divisible by y, then the result will be the remainder in the range [0, y-1]
(x % y) < (x / 2) ………if (x >= y)
(x % y) = x ……… if (x < y)
If y is 0, then division by zero is a compile-time error.

Example of Modulus Operator

Below is the C/C++ program to demonstrate the working of the modulo operator:

C

// C Program to illustrate the working of modulo operator
#include <stdio.h>
 
int main(void)
{
    int x, y;
 
    int result;
 
    x = 3;
    y = 4;
    // using modulo operator
    result = x % y;
    printf("%d", result);
 
    result = y % x;
    printf("\n%d", result);
 
    // for different values
    x = 4;
    y = 2;
    result = x % y;
    printf("\n%d", result);
 
    return 0;
}

C++

// C++ Program to demonstrate the working of modulo operator
#include <iostream>
 
using namespace std;
 
// Driver code
int main(void)
{
    int x, y;
 
    int result;
 
    x = 3;
    y = 4;
 
    // using modulo operator
    result = x % y;
    cout << result << endl;
 
    result = y % x;
    cout << result << endl;
 
    // for different values
    x = 4;
    y = 2;
 
    result = x % y;
    cout << result;
 
    return 0;
}
 
//    This code is contributed by Mayank Tyagi

Restrictions on the Modulo Operator

The modulo operator has quite some restrictions or limitations.

The % operator cannot be applied to floating-point numbers i.e float or double. If you try to use the modulo operator with floating-point constants or variables, the compiler will produce an error.

Example 1: C/C++ program to demonstrate the restrictions of the modulo operator.

C

// C Program to illustrate the working of modulo operator
#include <stdio.h>
 
int main(void)
{
    float x, y;
 
    float result;
 
    x = 2.3;
    y = 1.5;
 
    // modulo for floating point values
    result = x % y;
    printf("%f", result);
 
    return 0;
}

C++

// C++ Program to demonstrate the restrictions of modulo
// operator
#include <iostream>
using namespace std;
 
// Driver code
int main()
{
    float x, y;
 
    x = 2.3;
    y = 1.5;
 
    // modulo for floating point values
    result = x % y;
    cout << result;
 
    return 0;
}
 
// This code is contributed by Harshit Srivastava

Output

Compilation Error in C code :- prog.c: In function 'main':
prog.c:19:16: error:
 invalid operands to binary % (have 'float' and 'float')
     result = x % y;
                ^

Modulo Operator for Negative Operands

The sign of the result for the modulo operator is machine-dependent for negative operands, as the action takes as a result of underflow or overflow.

Example 2: C/C++ program to demonstrate the modulo operator for negative operands.

C

// C Program to illustrate the working of the modulo
// operator with negative operands
#include <stdio.h>
 
int main(void)
{
    int x, y;
 
    int result;
 
    x = -3;
    y = 4;
 
    // modulo for negative operands
    result = x % y;
    printf("%d", result);
 
    x = 4;
    y = -2;
    result = x % y;
    printf("\n%d", result);
 
    x = -3;
    y = -4;
    result = x % y;
    printf("\n%d", result);
 
    return 0;
}

C++

// C++ Program to demonstrate the working of the modulo
// operator for negative operands
#include <iostream>
using namespace std;
 
// Driver code
int main(void)
{
    int x, y;
 
    int result;
 
    x = -3;
    y = 4;
 
    // modulo for negative operands
    result = x % y;
    cout << result << endl;
 
    x = 4;
    y = -2;
    result = x % y;
    cout << result << endl;
 
    x = -3;
    y = -4;
    result = x % y;
    cout << result;
 
    return 0;
}
 
// This code is contributed by Harshit Srivastava