Write a C program to demonstrate post increment and pre increment operators

In C programming, the increment (++) and decrement (--) operators are used to increase or decrease a variable's value by 1. These operators can be applied in two forms: pre-increment/decrement and post-increment/decrement, which behave differently in expressions.

Syntax

/* Pre-increment/decrement */
++variable;
--variable;

/* Post-increment/decrement */
variable++;
variable--;

Pre-Increment Operator (++variable)

In pre-increment, the operator is placed before the operand. The value is first incremented and then the operation is performed on it.

For example −

z = ++a;    // First: a = a + 1, Then: z = a

Example

Following is an example for pre-increment operator −

#include <stdio.h>

int main() {
    int a = 10, z;
    z = ++a;
    printf("z = %d<br>", z);
    printf("a = %d<br>", a);
    return 0;
}

z = 11
a = 11

Post-Increment Operator (variable++)

In post-increment, the operator is placed after the operand. The value is incremented after the operation is performed.

For example −

z = a++;    // First: z = a, Then: a = a + 1

Example

Following is an example for post-increment operator −

#include <stdio.h>

int main() {
    int a = 10, z;
    z = a++;
    printf("z = %d<br>", z);
    printf("a = %d<br>", a);
    return 0;
}

z = 10
a = 11

Pre-Decrement Operator (--variable)

The decrement operator works similarly to increment but reduces the value by 1. In pre-decrement, the value is first decremented and then used in the expression.

Example

Following is an example for pre-decrement operator −

#include <stdio.h>

int main() {
    int a = 10, z;
    z = --a;
    printf("z = %d<br>", z);
    printf("a = %d<br>", a);
    return 0;
}

z = 9
a = 9

Post-Decrement Operator (variable--)

In post-decrement, the current value is used in the expression first, then the variable is decremented.

Example

Following is an example for post-decrement operator −

#include <stdio.h>

int main() {
    int a = 10, z;
    z = a--;
    printf("z = %d<br>", z);
    printf("a = %d<br>", a);
    return 0;
}

z = 10
a = 9

Key Points

• Pre-operators modify the variable before using it in the expression.
• Post-operators use the current value in the expression, then modify the variable.
• Both forms change the variable's value, but the timing affects the result of expressions.

Conclusion

Understanding the difference between pre and post increment/decrement operators is crucial for writing correct C programs. The choice between them depends on whether you need the original or modified value in your expression.