<span>Operating System is the software that gives the computer instructions on how to run applications. It is considered the most important program that runs on a computer because it manages all the hardware and software on it. It also controls the display/keyboard. </span>
The purpose of the conclusion paragraph is not only to wrap up the essay, but also to show the strong and central points in the essay alone. Since you are wrapping up the essay, it's your final paragraph and you have to clearly state all of your points and what and why the essay is written (depends on what you are talking about). But, the one purpose of an essay's conclusion is to clearly state the central points of the essay.
You'll need a helper variable for this, so depending on your programming language, the solution becomes:
int helper;
helper = arr[i];
arr[i] = arr[j];
arr[j] = helper;
