I'm asking for a homework tip (not [color="#ff0000"]help, emphasizing the word "help".) on how to complete this assignment.

I would rather be asking my professor why would you do this to a computer, and not take this assignment, but unfortunately he's out of state. Even unfortunately, it's for 5 grade points in his Operating System Concept class added to the entire semester. (That means, if you finish this assignment, you will earn 5 grade points on your total class grade. If you have 55 grade points, add 5 to it, and pass the class. I don't know what people called them, but the principles are the same.)

I was thinking of using a simple while loop, to allocate all of the RAMs given on an average computer and then try multithreading to achieve a busy 100% stable CPU, as according to the assignment tasks. But then, a classmate of mine said multithreading won't work that way, and was considering on idling the CPU to the maximum. But he doesn't know how to do it from there.

Usually, professors and other developers will try to avoid these programming tasks as much as possible. To be honest, I have no clue why he wanted to do this. So, I supposed it wouldn't hurt anybody to ask for help on this problem.

Yes, yes, all of you. I know to consequences of writing such a terrible terrible program, even if the program is the homework of our assignment here. But please do forgive me.

Note that if you want to get at all the RAM on a PC with more than about 2GB installed you'll need to use multiple processes or a 64-bit program.

You might find http://blogs.technet.com/b/markrussinovich/archive/2008/07/21/3092070.aspx useful.

Seconding the forkbomb. I wrote up a very simple forkbomb just now that completely locked up the computer in less than five minutes. Only took 5 lines of code. It didn't suck up all the CPU, but it sure ate up the RAM quick enough...

If you have a 64 bit OS then compile x64 so you can access all avaliable RAM. If you're compiling 32 bit, I'm pretty sure the OS will complain if your program tries to allocate more than 2GB total, so you'll need to spawn multiple processes (not threads).

I'd suggest running at least as many *logical* threads as your computer has, or you won't max out machines with hyperthreading. These threads can run infinite loops. If that doesn't keep you at 100%, then try allocating a *lot* of threads and have them all do the same. Context switching will incur considerable overhead.

If you really want to bring the system to it's knees, have these threads acquire critical sections in a chain which results in non-stop blocking and context switches. Your aim is not to cause deadlock, but have each thread being constantly blocked and unblocked.