Difference between ++i and i++ in C

1. Introduction

In C programming, ++i and i++ are increment operators, but they have different behaviors when used in expressions. Understanding the difference between these two is important for writing correct and efficient C code.

2. Key Points

1. ++i is the pre-increment operator, which increments the value of i before it is used in an expression.

2. i++ is the post-increment operator, which increments the value of i after it has been used in an expression.

3. The choice between ++i and i++ can affect the performance of loops in certain situations.

4. The value of i will be the same after the increment, regardless of whether you use pre-increment or post-increment.

3. Differences

++i (Pre-increment) i++ (Post-increment)
Increments i, then returns the value. Returns the value of i, then increments it.
More efficient in loops or functions as it doesn't need to store the original value. Less efficient as it requires storing the original value of i.

4. Example

#include <stdio.h>

int main() {
    int i = 5, j = 5, result1, result2;

    result1 = ++i; // Pre-increment
    printf("Pre-increment: i = %d, result1 = %d\n", i, result1);

    result2 = j++; // Post-increment
    printf("Post-increment: j = %d, result2 = %d\n", j, result2);

    return 0;


Pre-increment: i = 6, result1 = 6
Post-increment: j = 6, result2 = 5


1. In the pre-increment (++i), i is incremented first and then its value (6) is assigned to result1.

2. In the post-increment (i++), the original value of j (5) is assigned to result2, and then j is incremented to 6.

5. When to use?

- Use pre-increment (++i) when you do not need the original value of the variable, especially in loops for better performance.

- Use post-increment (i++) when you need to use the original value of the variable before it gets incremented.

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