In programming (Java, C, C++, JavaScript etc.), the increment operator ++ increases the value of a variable by 1. Similarly, the decrement operator -- decreases the value of a variable by 1.
a = 5 ++a; // a becomes 6 a++; // a becomes 7 --a; // a becomes 6 a--; // a becomes 5
Simple enough till now. However, there is an important difference when these two operators are used as a prefix and a postfix.
++ and -- operator as prefix and postfix
- If you use the
++operator as a prefix like:++var, the value of var is incremented by 1; then it returns the value. - If you use the
++operator as a postfix like:var++, the original value of var is returned first; then var is incremented by 1.
The -- operator works in a similar way to the ++ operator except -- decreases the value by 1.
Let's see the use of ++ as prefixes and postfixes in C, C++, Java and JavaScript.
Example 1: C Programming
#include <stdio.h>
int main() {
int var1 = 5, var2 = 5;
// 5 is displayed
// Then, var1 is increased to 6.
printf("%d\n", var1++);
// var2 is increased to 6
// Then, it is displayed.
printf("%d\n", ++var2);
return 0;
}
Example 2: C++
#include <iostream>
using namespace std;
int main() {
int var1 = 5, var2 = 5;
// 5 is displayed
// Then, var1 is increased to 6.
cout << var1++ << endl;
// var2 is increased to 6
// Then, it is displayed.
cout << ++var2 << endl;
return 0;
}
Example 3: Java Programming
class Operator {
public static void main(String[] args) {
int var1 = 5, var2 = 5;
// 5 is displayed
// Then, var1 is increased to 6.
System.out.println(var1++);
// var2 is increased to 6
// Then, var2 is displayed
System.out.println(++var2);
}
}
Example 4: JavaScript
let var1 = 5, var2 = 5;
// 5 is displayed
// Then, var1 is increased to 6
console.log(var1++)
// var2 is increased to 6
// Then, var2 is displayed
console.log(++var2)
The output of all these programs will be the same.
Output
5 6