Most programming languages (such as C#, Java, …) allow you to sort lists. Most of them also allow you to specify a sorting function so that you can customize the sort order. These functions usually take parameters a and b and define the return value as follows:

Return value	if
less than zero	a is less than b
equals zero	a is equal to b
greater than zero	a is greater than b

Usually you would do something like this (code in C#):

int Compare(int a, int b) {
  if (a < b) {
    return -1;
  }
  else if (a > b) {
    return 1;
  }
  else {
    return 0;
  }
}

However, when comparing int values, there’s a much quicker way to do this:

int Compare(int a, int b) {
  return a - b;
}

That’s it.