I've written a simple program to run in background, but it uses 100% of the CPU kernel. Is there a way to limit its use to 5% or less by modifying the code? I'm using Microsoft VC++ 6 Enterprise. I already know about the Task Manager method of prioritizing. That's not what I'm after.

If you are running in a tight loop, you should either have the app sleep or allow for Windows Messages to be processed. This is the only way to free up the cpu cycles without changing it's priority. Chi They mostly come at night...mostly.

So there's no way to calculate the current CPU use, then increase a sleep timer inrementally to lower the resource use? I need it to loop as fast as possible, but without a significant cost in other application performance. When I modify the source to run in console, it barely uses any CPU. Perhaps it's the Windows API?

It might depend on what you're doing. I have a program I wrote that runs in the background. The main part of the program is a small while(1) loop that breaks when the app receives the WM_QUIT message. To prevent it from eating the CPU I put Sleep(1000); at the end of the loop. Waiting a full second isn't really necessary if you want it to run faster. The smallest value you can use with Sleep() is 1 millisecond and on my 2GHz machine that still keeps the CPU usage at about 0%. Does putting Sleep(1); inside your loop let it run fast enough?

It uses 0% CPU, but it runs a bit too slow.