Memory vs. storage: Users try to figure out difference


February 22, 1993|By MICHAEL J. HIMOWITZ

New computer users are often confused by their machines, and one of the things that confuses them most is the difference between a computer's memory and storage capability.

For example, a friend once told me that he couldn't use his computer for word processing because it had "run out of memory." Actually, the machine had plenty of memory; he had just filled up the hard disk and couldn't save any more documents. An easy fix.

Another acquaintance complained that he couldn't run a program that required four megabytes of memory, when he knew quite well he had 40 megabytes available. He had 40 megabytes, all right, but that was on the hard disk. He had only one megabyte of memory available for programs, and he was stuck.

Actually, the confusion is easy because your computer stores data in two ways, and ads for computers will often talk about both types of capacity. Sometimes the people who put the ads together get them confused, too.

When most people refer to a computer's memory, they're referring to the chips inside the computer that are used for temporary storage of programs and data. This type of memory is also called RAM, or Random Access Memory.

The basic unit of storage is the byte, which is an electronic cubbyhole that can hold the equivalent of a single character

See HIMOWITZ, 16C, Col. 4 HIMOWITZ, from 13C

of text. A few years ago, when memory was relatively expensive, most people measured memory in kilobytes, units of 1,024 bytes. The first computer I bought back in 1983 had 16 kilobytes (16K) of RAM. The programs available for it were fairly crude.

Today, manufacturers install memory by the megabyte (roughly a million bytes). The computer on which this column was written has eight megabytes of RAM.

With more RAM, you can run more sophisticated programs, or multiple programs simultaneously. Today's graphical environments, such as Microsoft Windows, require gobs of memory. You won't find many computers on the market today with less than two megabytes of RAM, and most experts consider four megabytes the minimum for serious work. Luckily, memory is cheap today, generally less than $50 a megabyte.

The problem with RAM is that everything in it -- your programs, the letter you wrote to Aunt Rhode, or the budget figures you just ran through your spreadsheet -- disappear in a puff of electrons when you turn off the power switch. So you need someplace to store your programs and data permanently so you can load them into memory when you want them.

That's why computers have disk drives. They store your programs and data permanently -- or until you erase them. When you start your computer, it reads its underlying software -- known as the operating system, from the disk drive.

When you run a program such as a word processor spreadsheet, you're transferring it from a disk drive to the computer's internal memory, where it comes to life.

By the same token, those programs can then use the letters, budget figures or other data that you've stored on your disk. And when you're through working, the program will store your document, with all the changes you've made, back on a disk.

Drives come in two basic types, floppy drives that hold removable disks, and hard drives which are installed inside your computer. The floppy disks used in most computers today store a little over a megabyte of data. Hard disks typically store 40, 80, 100 or 200 megabytes of data, depending on how much you're willing to pay.

If you want to spend the money and you're a real pack rat, you can

buy drives that store more than a gigabyte (that's a billion bytes) of information.

To get some idea of how much storage this is, consider that the text of a decent-size novel will occupy less than one megabyte of disk space.

So 40 megabytes may sound like a lot at first. But software and graphic data files are so large today that a standard word processing program can occupy up to 15 megabytes of disk space. Even computer games can easily eat up five to 10 megabytes of storage.

As a result, floppy drives today are used primarily for transportation and archiving. When you buy a program, it comes on one or more floppy disks. You'll copy the program to your hard disk and run it from there.

Careful users will also use floppy disks to make backup copies of their

important data files in case the hard disk crashes (and every hard disk will eventually crash). Floppies are also used to transfer files from one computer to another.

If you start a report at work, you can store a copy on a floppy disk and take with you so that you can work on it with your home PC.

Another confusing issue is the physical size of a floppy disk, which is a separate issue from the amount of data the floppy can hold.

Most computers today come with drives designed for 3 1/2 -inch disks. Apple Macintosh computers use only 3 1/2 -inch drives. But until a few years ago, IBM-compatible computers came with 5 1/4 -inch drives as standard equipment, and many programs are still packaged on 5 1/4 -inch disks. If you're buying an IBM-compatible machine, it's a good idea to get both types of disk drives.

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