Assignment Operators in C with Clear Examples

1. Simple Assignment Operator (=)

The = operator stores a value into a variable. It is the most basic assignment operator and the one you will use the most.

The shape is simple:

Left_Operand = Right_Operand;

The value on the right side gets evaluated first, then stored in the variable on the left.

#include <stdio.h>

int main()
{
    int x = 10;
    int y = x;    /* y gets a copy of x's value */

    printf("x = %d\n", x);
    printf("y = %d\n", y);

    return 0;
}

x = 10
y = 10

Both x and y hold 10. Notice that y does not become linked to x — it just copies the value. Change x later and y stays at 10.

2. += Add and Assign

The += operator adds the right-hand value to the variable and stores the result back. Writing x += y is exactly the same as writing x = x + y, just shorter.

#include <stdio.h>

int main()
{
    int x = 10;
    int y = 10;

    x += y;   /* same as x = x + y */

    printf("x = %d\n", x);

    return 0;
}

x = 20

What happens step by step

When to use +=

• Adding to a running total: total += price;
• Counting: count += 1;
• Building sums in loops

3. -= Subtract and Assign

The -= operator subtracts the right-hand value from the variable and stores the result back. p -= q is the same as p = p - q.

#include <stdio.h>

int main()
{
    int p = 10;
    int q = 3;

    p -= q;   /* same as p = p - q */

    printf("p = %d\n", p);

    return 0;
}

p = 7

What happens step by step

When to use -=

• Deducting from a balance: balance -= withdrawal;
• Countdowns: time_left -= 1;
• Shrinking a quantity as items are consumed

4. *= Multiply and Assign

The *= operator multiplies the variable by the right-hand value and stores the result back. x *= y is the same as x = x * y.

#include <stdio.h>

int main()
{
    int x = 10;
    int y = 3;

    x *= y;   /* same as x = x * y */

    printf("x = %d\n", x);

    return 0;
}

x = 30

What happens step by step

When to use *=

• Doubling or scaling a value repeatedly
• Compounding growth in a loop: amount *= rate;
• Converting units where a constant scale factor applies

5. /= Divide and Assign

The /= operator divides the variable by the right-hand value and stores the result back. a /= b is the same as a = a / b. One important thing: if both sides are integers, C does integer division and drops the decimal part.

#include <stdio.h>

int main()
{
    int a = 8;
    int b = 2;

    a /= b;   /* same as a = a / b */

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

    return 0;
}

a = 4

What happens step by step

When to use /=

• Halving a value: x /= 2;
• Computing an average: avg /= count;
• Unit conversions that divide by a factor

6. %= Modulus and Assign

The %= operator divides the variable by the right-hand value and stores the remainder back. a %= b is the same as a = a % b. It works only with integers.

#include <stdio.h>

int main()
{
    int a = 7;
    int b = 2;

    a %= b;   /* same as a = a % b */

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

    return 0;
}

a = 1

What happens step by step

When to use %=

• Cycling an index: index %= size;
• Checking divisibility (after a %= 2, a is 0 or 1)
• Splitting numbers into digits in a loop

7. <<= and >>= Shift and Assign

These two operators work on the binary representation of a number. They shift the bits left or right by a given number of positions and store the result back.

The shape:

a <<= b;   /* same as a = a << b */
a >>= b;   /* same as a = a >> b */

Shifting left by 1 doubles the number. Shifting right by 1 halves it (dropping the remainder). You will not use these often in everyday C code, but they show up in performance-sensitive code and low-level work.

/* C program using <<= operator */
#include <stdio.h>

int main()
{
    int a = 7;   /* 7 in binary is 0111 */
    int b = 1;

    a <<= b;    /* same as a = a << b */

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

    return 0;
}

a = 14

7 in binary is 0111. Shift the bits one position left and you get 1110, which is 14 in decimal. Doubling 7 gives 14.

/* C program using >>= operator */
#include <stdio.h>

int main()
{
    int a = 7;   /* 7 in binary is 0111 */
    int b = 1;

    a >>= b;    /* same as a = a >> b */

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

    return 0;
}

a = 3

Shift 0111 one position right and you get 0011, which is 3. Halving 7 and dropping the remainder gives 3.

When to use <<= and >>=

• Fast multiplication or division by powers of two
• Bit manipulation in flags and masks
• Reading or packing binary data

Operator Precedence (Where Assignment Fits)

Assignment has the lowest precedence in C — only the comma operator sits below it. Everything on the right side gets evaluated before the value is stored. That is why a = b + c * 2; computes b + (c * 2) first, then assigns.