Stop running processes
Mac: View open processes with Activity Monitor
Sometimes, an application or process may be eating too much of your computer resources, slowing down your machine to a crawl.
To view open processes and computer resources usage, use the Activity Monitor.
To quickest way to access the Activity Monitor is by using Spotlight Search. Click the magnifying glass on the right side of the menu bar at the top of your screen, or press Command + Spacebar to open a Spotlight window and start typing the first few letters to auto-complete "Activity Monitor." Just press enter to access the tool.
Another way of accessing the Activity Monitor is through the Launchpad. The Activity Monitor is in the "Other" folder. Optionally, you could then drag its icon to the dock for easy access in the future.
Similar to Window's Task Manager, Mac's Activity Monitor displays a list of all your open processes with tabs for CPU, Threads, Idle Wake Ups and Network usage.
Force quitting open programs
To close any errant applications or applications that are not responding, you will have to Force Quit them.
To force quit open applications, click on the Apple logo on the top left side of the menu bar, then click on "Force Quit." This will show a window of all the open applications currently running on your Mac. Highlight one from the list then click the Force Quit button to close that particular application.
Alternatively, you could use the keyboard shortcut Command + Option + Escape to open the "Force Quit" window.
PC: Task Manager
There are a few ways to see what processes your computer is running. The easiest is to bring up Windows' built-in Task Manager. Just use the keyboard shortcut CTRL + SHIFT + ESC and go to the Processes tab.
Note: Windows 10 and 8 present process information in a much friendlier way than Windows 7 or Vista. If you're on Windows 7 or Vista, you'll probably want to pick up the program Process Explorer.
You'll see the process name, how much of your computer's processing power it's using, how much memory it's hogging and - sometimes - which programs use it.
So where do processes come in handy? Well, your computer might be feeling sluggish on a regular basis. Open up Task Manager and check the CPU and memory columns for each process.
You might find one process is using 100 percent - or close to it - of your CPU for a long period of time. Open up the program associated with the process and see what it's doing.
If it doesn't appear to be doing anything, restart it and keep an eye on it for a while to see if it starts hogging your processor again.
For essential programs performing important tasks, like security software, see if you can schedule the task for a time when you aren't using the computer.
For programs that don't appear to be doing anything but are using up resources, try updating the program to see if that helps. In the worst case, you might need to find a replacement that works better on your system.
Sometimes, programs that are acting up won't respond if you close them, so you have to stop the process directly. In Windows 10 or 8, select the process and click the End Task button.