Whether you’re a parent or a teacher, you probably want to limit not only where your kids can go on the Web, but also what they can do on your computer. After all, what good does it do to limit their Web surfing if they can just load Microsoft Internet Explorer or Apple’s Safari browser and get around the limits that you’ve set up? And if you’re a teacher, you may want your students to only use BumperCar while you’re teaching, or you may find them going off on non-educational tangents.

Luckily, Apple built a feature into Mac OS X that gives you the control you need. It’s the user function. When you installed Mac OS X, you probably set yourself up as the default user, which is also known as the admin. This is the account that gives you complete control over your Mac, and it’s probably not the one you want your kids to use.

Instead, you’ll want to set up new user accounts for them; those accounts will keep them out of your personal information because everything in your Home folder will be off-limits. To create new accounts, open System Preferences and click on Accounts. You’ll see the list of accounts on your computer on the left and a series of panes on the right. At the bottom of the list of windows you’ll notice plus and minus buttons. Click the plus button.

Now you’ll notice that a new user appears in the window above. To the right, you can enter that person’s name and give them a password. You can also click on the Picture pane to give them a picture that’s shown next to their name in the Mac OS X login window.

Next, click on the Limitations pane. (We’ll get to Security in a moment.) Click on “Some Limits” under “This user needs:”. Under “This user can:”, uncheck any of the functions that you don’t want them to perform. You probably won’t want them to open the System Preferences, and you may want to keep them from changing their password in case you want to log in under their account occasionally.

In the box under that, you can limit which applications this new user can access. Click the box next to “This user can only use these applications:” and check the boxes next to the applications they can use, including BumperCar. If you installed BumperCar somewhere other than the Applications folder, click the “Locate...” button and find the application; now it will show up in the “Others” folder in the application list.

You can select the check box under “Allow” to give the user access to everything in the folder on the right, but you probably won’t want to do that with the Applications folder, so click the “Uncheck All” button at the bottom to deselect everything in that folder. Now check each application that this user should be able to access. Do the same for the other folders.

You’ll notice that this new user has the word “Managed” under their name in the list to the left. That means they’re not an admin and they can’t make crucial changes to the computer. Finally, click “Login Options” at the bottom of that list and take the check mark off the box next to “Automatically log in as.” Now anyone who starts the computer will see a login window and they will have to choose their user name and enter their password to use it.

To make sure no one else can get into the Security pane and possibly set a master password without you knowing it, (if you accidentally leave your computer logged in, for example,) click the lock in the bottom left corner. Now if someone tries to unlock it, they will need an admin password.

Finally, when you’re done using your Mac, click on the Apple menu and select “Log Out [user name]...”. That will log you out and bring your computer to the login window, where you can put it to sleep if you want. The next person to use it will have to click their user name and enter their password.