Keyboards

After the operating system prepares the computer for use, you have to tell it what to do, usually by sending commands through the keyboard or mouse.

A keyboard is equipped with letter keys like a typewriter, plus a variety of special controls, such as cursor directional keys, page up/down to scroll documents, and "home" to move a cursor to the top of a document. When a mouse is installed, many cursor control keys may rarely be used.

Most keyboards have a numeric keypad on the right-hand side. Look for this if you will use your computer for bookkeeping or statistical work.

Function keys, aligned across the top of the keyboard, enable commands such as save, print, copy and delete. These keys, numbered from F1 to F12, are preprogrammed by different software programs to perform different jobs. The program may include a plastic template that fits over the function keys to identify those jobs.

Extended keyboards offer additional keys and features to use with specialized software.

You can program a sequence of keys yourself to automate certain functions. These keyboard shortcuts are called macros.

Mouse Variations

The mouse is connected by wire to your desktop PC. Laptops and notebook computers come with miniature track buttons or scratch pads, though there is often a port that allows connection of a mouse.

• Mouse. A small, palm-sized object with a ball imbedded on its underside, the mouse can replace the function and control keys for many activities. Rolling the mouse downward moves the cursor correspondingly downward on the screen. Clicking a button on the mouse activates commands such as selecting print size or formatting documents. Holding down this click button while moving the cursor allows you to drag sections of a document and place them elsewhere.
• Track ball. Essentially an upside-down mouse, the track ball is a billiard-sized ball that sits in a permanent base. You roll the ball to move the cursor. A track ball is useful if you do not have enough desktop space to move and manipulate a mouse.
• Scratch pad. With your finger, you trace a path on this pad to move the cursor, then tap the pad to activate a function.

Scanners

A scanner digitally copies a flat image like a photocopy machine, but translates it into a format your computer can display instead of creating a paper copy.

Once you scan an image, special software lets you manipulate it by adding or removing elements, changing colors, resizing, reversing and retouching.

A scanner also can scan text from a book or magazine, special software translates the image into text for word processing.

Scanners read images in pixels (picture elements). The most basic scanner scans at 300 dots per inch, but many scanners have higher resolutions.

The higher the resolution, the better the reproduction.

Digital Cameras

A digital camera captures photographs on magnetic media instead of film. The media can be used over again and there is no film to develop.

Images can be downloaded into a computer by a cable connecting the two devices, or by placing the camera's floppy into the computer.

Computer images are often stored as JPEGs (pronounced JAY-pegs), an acronym for Joint Photographic Experts Group.

Most cameras allow you to choose from varying JPEG resolutions; the lower the resolution, the more pictures you'll be able to store on a disk.

Multimedia Input Devices

Most computers can now manipulate complex image and sound files, and there are various ways to input them to your computer.

• Microphone. Multimedia computers can manipulate sound in much the same way they manipulate text and graphics. You can input music, amend files and documents with voice messages, and use your computer as a telephone answering machine.
• Graphics tablet. A special surface on which you can draw with a stylus. Your work appears on the monitor screen and can be saved.
• Camcorder. Your computer can capture video and sound via standard A/V jacks. The processing power of your computer determines the quality, size and length of these movies, and your ability to edit them.