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In any programming (Java, C Programming, PHP etc. ), increment ++ and decrement -- operator are used for increasing and decreasing the value of operand by 1 respectively.

Suppose, a=5 then,
++a; //a becomes 6
a++; //a becomes 7
--a; //a becomes 6
a--; //a becomes 5

Simple enough till now but, there is a slight but very important difference that a programmer should remember while using these operators.

++ and -- operator as prefix and postfix

If you use ++ operator as prefix like: ++var; then, the value of operand is increased by 1 then, only it is returned but, if you use ++ as postfix like: var++; then, the value of operand is returned first then, only it is increased by 1.

This is demonstrated by an example in these 4 different programming languages.

Languages
C Programming
C++ Programming
PHP
Java

C Programming Example

#include <stdio.h>
int main(){
int var=5;
printf
("%d\n",var++);
/* 5 is displayed then, only var is increased to 6 */
printf
("%d",++var);
/* Initially, var=6 then, it is increased to 7 then, only displayed */
return 0;
}

C++ Programming Example

#include <iostream>
using namespace std;
int main(){
int var=5;
cout
<<var++<<"\n";
/* 5 is displayed then, only var is increased to 6 */
cout
<<++var<<"\n";
/* Initially, var=6 then, it is increased to 7 then, only displayed */
return 0;
}

PHP Example


<?php
Svar=5;
echo $var
++."<br/>";
echo
++$var;
?>

Java Example


class Operator {
public static void main(String[] args){
int var=5;
System.out.println(var++);
System.out.println("\n"+ ++var);
}
}

Output of all these program is same as below:


5
7

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