Jaggies

Slang term for the jagged edges that you'll see along the sides of curves, graphics or round characters. Jaggies occur because the printer can only print individual dots rather than smooth lines .

Jitter

A fault on a monitor that causes annoying, tiny movements of characters .

Joystick

A device that lets you control the movement of a cursor by tilting an upright rod. To use a joystick, you'll need to fit a joystick controller card inside your PC. The first PCs had joystick ports fitted, but now it's common for the soundcard to provide the joystick ports. The port itself looks like a serial port connector with nine pins in a D-shaped surround.

JPEG

A standard you may come across if you use graphic images. JPEG is a complex way of storing images in a compressed format so they take up a much less disk space .

Jukebox

A jukebox is a sophisticated CD-ROM drive that can hold several CD-ROM discs and select the correct disc when required. Jukeboxes are not meant for just one user; they connect to a network and can contain hundreds of standard CD-ROM discs that many users need to access .