C Increment and Decrement Operators – Make Counters Easy

In C programming, increment (++) and decrement (--) operators are used to increase or decrease a variable’s value by 1. They’re compact and commonly used in loops, counters, and algorithms.

Types of Increment and Decrement Operators

Operator	Description
`++`	Increments value by 1
`--`	Decrements value by 1

These can be used in two forms:

Prefix (++x, --x)
Postfix (x++, x--)

Pre-Increment and Post-Increment

Pre-Increment (`++x`)

Increments the value before it’s used in an expression.

int x = 5;
int y = ++x; // x becomes 6, then y is assigned 6

Post-Increment (`x++`)

Uses the value first, then increments it.

int x = 5;
int y = x++; // y is assigned 5, then x becomes 6

Pre-Decrement and Post-Decrement

Pre-Decrement (`--x`)

Decreases the value before use.

int x = 5;
int y = --x; // x becomes 4, then y = 4

Post-Decrement (`x--`)

Uses the value, then decreases it.

int x = 5;
int y = x--; // y = 5, then x becomes 4

Full Example

#include <stdio.h>

int main() {
    int a = 5, b, c;

    b = ++a;  // Pre-increment: a becomes 6, b = 6
    printf("After pre-increment: a = %d, b = %d\n", a, b);

    c = a++;  // Post-increment: c = 6, then a becomes 7
    printf("After post-increment: a = %d, c = %d\n", a, c);

    --a;      // Pre-decrement: a becomes 6
    printf("After pre-decrement: a = %d\n", a);

    a--;      // Post-decrement: a becomes 5
    printf("After post-decrement: a = %d\n", a);

    return 0;
}

Output:

Use Cases / Example

Loop

for(int i = 0; i < 10; i++) {
    printf("%d ", i);
}

Best Practices

Tip	Why It Helps
Prefer `++i` in loops	Often more efficient in C (minor gain)
Avoid using `++` and `--` in complex expressions	Reduces confusion
Use increment/decrement sparingly in conditions	Increases readability

Common Mistakes

Mistake	Problem
Using `x++` in `printf()` and expecting updated value	Outputs old value
Using multiple increments in one statement	Leads to undefined behavior