Home computer primer

Here is a brief look at what makes personal computers tick -- plus a price list of leading home computers.

OK, the brain of a personal computer is a tiny microprocessor, a small chip that handles the functions performed by the central processing unit (CPU) in a large computer. The microprocessor uses information stored in two kinds of memory chips: ROMs (read-only memory) and RAMs (random-access memory). ROM is permanent; when you turn the power off, its memory doesn't disappear. It carries the very basic operating instructions for a computer. RAM is extra memory capacity. If the power goes, so does anything in RAM -- forever.

Memory is measured in bits and bytes -- different names for characters. Eight bits equal one byte. Thousands of bytes are measured in kilobytes, ''K'' for short. One page of double-spaced type is just about equal to 1K of memory -- or 1,000 bytes.

To avoid losing information from your RAM, you will need to store it on a tape cassette or a floppy disk which looks like a small flexible record. To get information from your computer to your cassette or disk, you will need a cassette recorder or a disk drive.

You will probably also want to consider such hardware as a printer and a modem, which allows you to hook up to data bases via the phone.

Now that you've mastered the vocabulary, here's a brief look at what awaits the consumer looking for home-oriented computers.

Apple: The Apple II Plus has the most software available, excellent color graphics, 48K of memory, and decent word processing. It's got a "hood" you open and in there lies the best thing going for it -- more room to add memory and features. This makes the Apple versatile.

Apple II Plus: $1,530 to $5,000.

IBM: The IBM personal computer has a CPU that handles information in chunks twice as large as other personal computers, giving it a speed advantage. It is tops in this respect. Like Apple, it has tremendous versatility due to add-on room.

IBM personal computer: $1,565 to $6,000.

Radio Shack: Radio Shack offers four personal computers. The TRS-80 model III has limited black and white graphics capabilities, and a built-in video screen. The TRS-80 Color Computer is the only Radio Shack computer with color graphics.

TRS-80 Model III: $699 to $5,000.

TRS-80 Color Computer: $399 to $2,000.

Atari: The Atari 400 features a smooth, touch keypad -- useless for fast touch typers but great for kids' sticky fingers. The Atari 800 has the standard raised keyborad. Both use you TV for a video screen.

Atari 400: $399 to $2,000.

Atari 800: $899 to $4,000.

Sinclair: The British Sinclair ZX81 is a great way to acquaint yourself with computer progeamming, but with 1K of memory (expandable to 16K) and smooth keypad, it's of limited use.

ZX81 assembled: $149.95.

ZX81 unassembled: $99.95.