Increment (++) and Decrement (--) Operator as Prefix and Postfix

Increment and Decrement Operator

In programming (C, C++ etc. ), the increment operator ++ increases the value of a variable by 1. Similarly, the decrement operator -- decreases the value of a variable by 1.

For Example:- let's understand increment and decrement as prefix and postfix.

a = 2
++a;          // a becomes 3
a++;          // a becomes 4
--a;          // a becomes 3
a--;          // a becomes 2

Simple enough till now. However, there is a slight but important difference you should know when these two operators are used as prefix and postfix.

++ and -- operator as prefix and postfix

• If you use the ++ operator as "prefix" like: ++var. The value of var is incremented by 1 then, it returns the value.
• If you use the ++ operator as "postfix" like: var++. The original value of var is returned first then, var is incremented by 1.
• The -- operator works in a similar way like the ++ operator except it decreases the value by 1.

Let's see the use of ++ as prefix and postfix in C, and C++

Example 1: C Programming increment operator as prefix and postfix

// C programming example to understand the increment operator as prefix and postfix.
#include <stdio.h>
int main() {
    int var1 = 2, var2 = 2;

    // var1 is displayed
    // Then, var1 is increased to 3.
    printf("var1=%d\n", var1++);

    // var2 is increased to 3 
    // Then, it is displayed.
    printf("var2=%d\n", ++var2);
                                
    return 0;
}

Output

var1=2
var2=3

Example 2: C programming Decrement operator as prefix and postfix.

We can convert a char array to double by using the std::atof() function.

For Example :-

// C programming example to understand the decrement operator as prefix and postfix.
#include <stdio.h>
int main() {
    int var1 = 2, var2 = 2;

    // var1 is displayed
    // Then, var1 is decreased to 1.
    printf("var1=%d\n", var1--);

    // var2 is decreased to 1 
    // Then, it is displayed.
    printf("var2=%d\n", --var2);
    return 0;
}

Output

var1=2
var2=1

Example 3: C++ Increment operator as prefix and postfix.

This function accepts a number (can be any data type) and returns the number in the desired string.

// C++ programming example to understand the increment operator as prefix and postfix.
#include <iostream>

using namespace std;

int main() {
    int var1 = 2, var2 = 2;

    // var1 is displayed
    // Then, var1 is increased to 3.
    cout << "var1=" << var1++ << endl;

    // var2 is increased to 3
    // Then, it is displayed.
    cout << "var2=" << ++var2 << endl;

    return 0;
}

Output

var1=2
var2=3

Example 4: C++ decrement operator as prefix and postfix.

// C++ programming example to understand the decrement operator as prefix and postfix.
#include <iostream>

using namespace std;

int main() {
    int var1 = 2, var2 = 2;

    // var1 is displayed
    // Then, var1 is decrease to 1.
    cout << "var1=" << var1-- << endl;

    // var2 is increased to 1
    // Then, it is displayed.
    cout << "var2=" << --var2 << endl;

    return 0;
}

Output

var1=2
var2=1

We hope that this tutorial helped you develop better understanding of the concept of Increment-Decrement-operator-difference-prefix-postfix in C++.

Keep Learning : )