Become a Guest on Your Own Computer

A: Administrator accounts on a Windows, Mac or Linux computer have the ability to adjust settings, install new programs, change passwords and perform other functions that affect the entire system. Accounts designated as “standard,” “limited” or “guest” have much less control over the entire system and can make only minor changes that are specific to that account, like changing the desktop wallpaper. Malicious software that invades a computer through the user logged in as the administrator can usually burrow in deeper to do more damage.

To set up a limited account for yourself (or a child) on a Windows 10 Home or Professional system, go to the Start menu and select the gear-shaped Settings icon. On the Settings screen, choose Accounts, then “Family & other people” to “Add someone else to this PC.” Follow the instructions on the screen to create the account. As with most account creation, you may need to enter the administrator password at some point.

On a Windows 7 system, go to the Start menu and select Control Panel and then “User Accounts and Family Safety.” Click User Accounts and then “Manage another account.” Click “Create a new account” and follow the steps on the screen.

Mac administrators can set up the less powerful Standard accounts, Managed accounts with Parental Controls, or Sharing-only accounts for screen- and file-sharing. To get started, go to the Apple menu and choose System Preferences. In the System Preferences box, click Users & Groups. In the Users & Groups box, click the padlock icon, enter the Mac’s administrator password and click the plus (+) icon to get started.

— Why a Digital Photo Can Look Fuzzy

A: The “pixel” (short for picture element) is a tiny segment of visual data and the basic unit of measurement when talking about digital-photo resolution. Rows of pixels create the image. In general, the more pixels per inch (ppi), the sharper that image tends to be, thanks to the “higher” resolution.

On a Mac, you can quickly see the pixel dimensions and resolution of an image by selecting its desktop icon and pressing the Command and I keys to open the Info box; Windows users can right-click the icon and look in the Properties box. You can also find the information by opening the image in a photo-editing program.

Printers measure resolution in (ink) dots per inch, or dpi. While pixels-per-inch and dots-per-inch are not the same, the higher the dpi, the finer the quality of the printed photo. A standard resolution for printed photos is 300 dpi.

When preparing to print a digital picture, consider the size of the print itself, like 4 inches by 6 inches. The ScanTips site has a calculator at www.scantips.com/calc.html that you can use to convert pixel dimensions for printing at 300 dpi on a specific paper size.

For a rule of thumb, if you want to know the maximum size that a file can be printed and maintain its visual quality, divide its pixel dimensions by 300. A picture with pixel dimensions of 640 pixels wide by 480 pixels high will print at slightly more than 2 inches wide by 1.6 inches high, while an image with a higher resolution of 3,768 pixels by 2,512 pixels should look fine as a 12-by-8-inch print. Commercial shops for scanning and printing may have their own guidelines, as do many photography websites.