In programming, “++i” and “i++” are both used to increment the value of a variable by 1, but the difference is in the order in which the increment operation and the use of the variable occur.

When it comes to the difference between “++i” and “i++”, it’s important to understand how each operator works. “++i” is known as the pre-increment operator, which increments the value of ‘i’ immediately and returns the incremented value. On the other hand, “i++” is known as the post-increment operator, which increments the value of ‘i’ but returns the original value that ‘i’ held before being incremented.

Example:

#include <iostream>
using namespace std;

void print(int x)
{
    cout << x << endl;
}

int main()
{
    int n = 5;

    print(n++);
    print(n);
    print(++n);

    return 0;
}

/* Output:
5
6
7
*/

In terms of performance, “++i” is sometimes faster than “i++” and is never slower than "i++". For intrinsic types like int, it doesn’t matter: “++i” and “i++” are the same speed. However, for class types like iterators, “++i” very well might be faster than “i++” since the latter might make a copy of the this object.

In conclusion, while there may be some performance differences between “++i” and “i++”, it’s generally recommended to use “++i” unless you specifically want the postfix semantics.

I hope this information will be helpful to you.