C C++

C Arithmetic Operators

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Introduction

Arithmetic operators are used to perform mathematical calculations in C. They allow you to add, subtract, multiply, divide, and find the remainder of numbers. These operators are among the most frequently used operators in C programming and are essential for solving computational problems.

Whether you are calculating a total, averaging scores, incrementing a counter, or performing scientific calculations, arithmetic operators play a fundamental role in almost every C program.

What Are Arithmetic Operators?

An arithmetic operator performs a mathematical operation on one or more operands and produces a numeric result.

Syntax

operand operator operand

For example, in the expression a + b, a and b are operands, while + is the arithmetic operator.

List of Arithmetic Operators

Operator Name Description Example
+ Addition Adds two operands. a + b
- Subtraction Subtracts the right operand from the left operand. a - b
* Multiplication Multiplies two operands. a * b
/ Division Divides the left operand by the right operand. a / b
% Modulus Returns the remainder after integer division. a % b

Addition Operator (+)

The addition operator adds two numeric values together.

Example

#include <stdio.h>

int main(void)
{
    int a = 12;
    int b = 8;

    printf("%d\n", a + b);

    return 0;
}

Output

20

Subtraction Operator (-)

The subtraction operator subtracts the second operand from the first operand.

Example

#include <stdio.h>

int main(void)
{
    int a = 20;
    int b = 7;

    printf("%d\n", a - b);

    return 0;
}

Output

13

Multiplication Operator (*)

The multiplication operator multiplies two operands.

Example

#include <stdio.h>

int main(void)
{
    int width = 5;
    int height = 4;

    printf("%d\n", width * height);

    return 0;
}

Output

20

Division Operator (/)

The division operator divides one operand by another. The result depends on the data types of the operands.

Integer Division

When both operands are integers, the fractional part is discarded.

Example

#include <stdio.h>

int main(void)
{
    printf("%d\n", 10 / 3);

    return 0;
}

Output

3

Floating-Point Division

If at least one operand is a floating-point value, the result includes the decimal part.

Example

#include <stdio.h>

int main(void)
{
    printf("%.2f\n", 10.0 / 3);

    return 0;
}

Output

3.33
Warning: Integer division truncates the fractional part instead of rounding the result.

Modulus Operator (%)

The modulus operator returns the remainder after integer division.

Example

#include <stdio.h>

int main(void)
{
    printf("%d\n", 17 % 5);

    return 0;
}

Output

2

The modulus operator can only be used with integer operands.

Tip: The modulus operator is commonly used to determine whether a number is even or odd.

Example

if (number % 2 == 0)
{
    printf("Even\n");
}
else
{
    printf("Odd\n");
}

Unary Plus and Unary Minus

Besides their binary forms, the + and - operators can also be used as unary operators.

Operator Description Example
+ Indicates a positive value. +a
- Negates the operand. -a

Example

int a = 10;

printf("%d\n", -a);

Output

-10

Operator Precedence

Arithmetic operators follow a predefined order of evaluation called operator precedence.

Precedence Operators Associativity
Highest + - (Unary) Right to Left
* / % Left to Right
Lowest + - (Binary) Left to Right

For example:

Example

int result = 5 + 4 * 3;

The multiplication is performed first.

Output

17
Tip: Use parentheses to make expressions easier to understand and avoid mistakes caused by operator precedence.

Example

int result = (5 + 4) * 3;

Common Beginner Mistakes

  • Expecting integer division to return a decimal value.
  • Using the modulus operator with floating-point numbers.
  • Ignoring operator precedence.
  • Dividing by zero, which results in undefined behavior.
  • Using integer types when floating-point calculations are required.
Warning: Dividing an integer by zero or using the modulus operator with zero as the divisor causes undefined behavior and should always be avoided.

Complete Example

The following program demonstrates all arithmetic operators.

Example

#include <stdio.h>

int main(void)
{
    int a = 20;
    int b = 6;

    printf("Addition: %d\n", a + b);
    printf("Subtraction: %d\n", a - b);
    printf("Multiplication: %d\n", a * b);
    printf("Division: %d\n", a / b);
    printf("Remainder: %d\n", a % b);

    return 0;
}

Summary

Arithmetic operators perform basic mathematical operations and are used in nearly every C program.

Operator Operation
+ Addition
- Subtraction
* Multiplication
/ Division
% Modulus (Remainder)

Understanding how arithmetic operators work—including integer division, the modulus operator, unary operators, and operator precedence—provides a solid foundation for writing calculations, algorithms, and more advanced C programs.

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