Assignment Operators in C

An assignment operator is used to store a value in a variable or modify the value of an object.

int age;

age = 20;

Here, 20 is assigned to the variable age.

The = operator assigns the value of the expression on its right to the object on its left.

int number;

number = 50;

printf("%d", number);

Output:

50

A variable can be declared and initialized at the same time.

int marks = 80;

Here, the variable marks is created and initialized with 80.

int age = 20;

age = 25;

printf("%d", age);

Output:

25

The old value is replaced by the new value.

int a = 10;
int b;

b = a;

printf("%d", b);

Output:

10

The current value of a is assigned to b.

int a = 10;
int b = 20;

int sum;

sum = a + b;

printf("%d", sum);

Output:

30

The expression on the right side is evaluated before its result is assigned to sum.

The = operator performs assignment, while == is a relational operator used to compare two values.

int age = 20;

if (age == 20)
{
    printf("Age is 20");
}

Do not confuse = with ==.

int number = 10;

number += 5;

printf("%d", number);

Output:

15

The statement number += 5; is equivalent to number = number + 5;.

int number = 20;

number -= 5;

printf("%d", number);

Output:

15

It is equivalent to number = number - 5;.

int number = 10;

number *= 3;

printf("%d", number);

Output:

30

It is equivalent to number = number * 3;.

int number = 20;

number /= 4;

printf("%d", number);

Output:

5

It is equivalent to number = number / 4;.

int number = 17;

number %= 5;

printf("%d", number);

Output:

2

It is equivalent to number = number % 5;.

Assignment can be chained because an assignment expression itself has a value.

int a, b, c;

a = b = c = 10;

printf("%d %d %d", a, b, c);

Output:

10 10 10

int price = 100;
int quantity = 5;
int total;

total = price * quantity;

printf("Total = %d", total);

Output:

Total = 500

The calculation is performed first, and the result is assigned to total.

float price;

price = 99.50f;

printf("%.2f", price);

Output:

99.50

Assignment operators can also be used with floating-point variables.

float price = 100.0f;

price += 25.5f;

printf("%.2f", price);

Output:

125.50

The += operator can be used with compatible arithmetic types.

char grade;

grade = 'A';

printf("%c", grade);

Output:

A

A character can be assigned to a char variable.

#include <stdio.h>

int main()
{
    int number;

    printf("Enter a number: ");
    scanf("%d", &number);

    number += 10;

    printf("Result = %d", number);

    return 0;
}

The value entered by the user is updated using the compound assignment operator +=.

int count = 0;

count += 1;
count += 1;
count += 1;

printf("%d", count);

Output:

3

Compound assignment operators are useful for updating counters and totals.

#include <stdio.h>

int main()
{
    int total = 0;

    for (int i = 1; i <= 5; i++)
    {
        total += i;
    }

    printf("Total = %d", total);

    return 0;
}

Output:

Total = 15

The += operator updates the total during every iteration.

C also provides compound assignment operators for bitwise operations.

unsigned int a = 7;
unsigned int b = 3;

a &= b;

printf("%u", a);

Output:

3

The statement is equivalent to a = a & b;.

unsigned int a = 4;
unsigned int b = 2;

a |= b;

printf("%u", a);

Output:

6

The statement is equivalent to a = a | b;.

unsigned int a = 7;
unsigned int b = 3;

a ^= b;

printf("%u", a);

Output:

4

The statement is equivalent to a = a ^ b;.

unsigned int number = 4;

number <<= 1;

printf("%u", number);

Output:

8

The left-shift assignment operator shifts the bits to the left and assigns the resulting value back to the variable.

• Confusing = with ==.
• Forgetting to initialize variables when their value is needed immediately.
• Dividing by zero when using /=.
• Using %= with floating-point operands.
• Using incompatible types without understanding the conversion involved.
• Forgetting that compound assignment updates the existing value.
• Using a variable before it has a meaningful initialized value.

#include <stdio.h>

int main()
{
    int number = 100;

    printf("Initial = %d\n", number);

    number += 20;
    printf("After += 20: %d\n", number);

    number -= 10;
    printf("After -= 10: %d\n", number);

    number *= 2;
    printf("After *= 2: %d\n", number);

    number /= 5;
    printf("After /= 5: %d\n", number);

    number %= 7;
    printf("After %%= 7: %d\n", number);

    return 0;
}

#include <stdio.h>

int main()
{
    int number;

    printf("Enter a number: ");
    scanf("%d", &number);

    number += 5;
    number *= 2;
    number -= 10;

    printf("Final value = %d", number);

    return 0;
}

This program demonstrates how multiple compound assignments can update a variable step by step.

Practice the following programs:

1. Assign a value to an integer variable.
2. Assign one variable's value to another variable.
3. Add a value using +=.
4. Subtract a value using -=.
5. Multiply a value using *=.
6. Divide a value using /=.
7. Find a remainder using %=.
8. Use assignment operators inside a loop.
9. Use bitwise assignment operators with unsigned integers.
10. Create a simple calculator using assignment and arithmetic operators.

Practice these operators until you are comfortable with updating variable values using both simple and compound assignment.