Performance Difference Between i++ and ++i in C++

There is a big distinction between the suffix and prefix versions of ++.

• In the prefix version (i.e., ++i), the value of i is incremented, and the value of the expression is the new value of i. So basically it first increments then assigns a value to the expression.

• In the postfix version (i.e., i++), the value of i is incremented, but the value of the expression is the original value of i. So basically it first assigns a value to expression and then increments the variable.

Let's look at some code to get a better understanding.

Example Code

#include<iostream>
using namespace std;
int main() {
   int x = 3, y, z;
   y = x++;
   z = ++x;
   cout << x << ", " << y << ", " << z;
   return 0;
}

Output

5, 3, 5

Let's look at it in detail

• Initialize x to 3

• Assign y the value we get by evaluating the expression x++, ie, the value of x before increment then increment x.

• Increment x then assign z the value we get by evaluating the expression ++x, ie, value of x after the increment.

• Print these values