Pittsburgh — When you buy a personal computer, it's tempting to show it off. The monitor, CPU, and keyboard look so impressive sitting there on the desk. Unfortunately, it doesn't mean much. It's the software inside your computer that counts.
Software tells the hardware what to do. Word-processing software translates my keystrokes into these words. Operating-system software gives computers their ''feel.''
So the software you put inside your computer is going to play a key role in whether you have a good experience with the technology. Pick it carefully.
In all likelihood, your new computer will come with some software installed. Typically, it will have an operating system and some basic programs to get you started.
Sometimes this will be all you need. Still, it doesn't hurt to make a checklist of the programs you expect to use. That way, you can buy the hardware and the software at the same time and have the dealer install it for you.
The key software, of course, is going to be the program that you can't wait to use. Maybe it's a word-processing program to help you write letters; or that special look at Beethoven's Fifth Symphony. Whatever it is, you've pinned it down by now. That piece of software is the main reason you're buying a computer.
Of course, you'll need other software too. This article will take you on a tour of software that makes sense.
The one program that's absolutely necessary on every computer is operating-system software. For an IBM-compatible, this software is called Windows or DOS. Windows is rapidly replacing DOS, and if you have an older DOS-based machine, by all means try to upgrade to Windows, which is simpler and more natural to use. With Windows, you can point-and-click your way through programs rather than typing obscure commands. Windows will also run older DOS programs.
Of course, you can make do with DOS, especially if you're getting an older machine that can't handle Windows. The drawback is that you won't be able to run future versions of software, which will be Windows-based. Today, Microsoft Corporation released the latest version of its program, Windows 95, which does away with DOS completely. We won't spend any more time dealing with DOS here.
If you're buying a Macintosh, it will probably come loaded with System 7.5. (The numbers refer to the version of the software. Since most software companies upgrade their programs every year or two, they need some way to distinguish them. If a new version is a significant upgrade, companies typically jump a whole number - from ClarisWorks 3.0 to 4.0, for example. If it's a small upgrade, the version usually moves up one-tenth: WordPerfect for Windows 6.0 to 6.1.)
Advocates for Windows and System 7.5 argue endlessly about which is better. But the real trend is that they're becoming more alike. Both are picture-based rather than command-based. You will most likely use a computer mouse to move around the screen and issue commands. Don't worry if the mouse seems to zig and zag crazily at first. It takes several days to get coordinated.
Whichever system you get, the pictures will be supplemented by a menu at the top of the screen with words such as ''File'' and ''Edit.'' Click on them and a menu appears with even more commands. Gradually, you will learn your way around. Both Windows and System 7.5 try hard to be so easy that you don't need to read the manuals. But they're available if you need them.
The operating systems also include basic programs, such as simple word-processing and communications software. That means you can write a letter without buying extra software. Such programs probably won't allow you to format a doctoral thesis - they don't have all the bells and whistles. But they are adequate for simple communications.
Of course, your favorite program will be where you spend your learning time. You'll find that with either System 7.5 or Windows, one program works pretty much like another. You'll use the same procedures to open and close them. Their menus will be in the same place. Once you master one program, the next one will be easier to learn.
This is not the case with some DOS-based games and programs for IBM-compatibles. These may not even run without tweaking the operating system a little. This is the time to call on your computer buddy.
There's one type of software program you should strongly consider getting. It's called a utilities program, but it's actually a package of utility programs. These keep your hard drive in good working order. They check out the system to make sure nothing is going awry. Most importantly, they can help you recover from glitches, which remain all too common in the computer world. I can't tell you how many times the power has gone out suddenly or I've accidentally deleted something and been able to recover it using a utilities program. My favorite is Norton Utilities, which has saved me hours of rewriting.
Such software companies sell additional programs that you may find valuable. One is backup software. It can be set to make daily or weekly copies of your most important files. If you have lots of files, the software can make back ups to special data cassettes that run in a tape drive. (See story in yesterday's Monitor for a discussion of the hardware to use for backups.)
The other utility add-on is anti-virus software. These programs protect your machine from computer viruses, nasty man-made software that aims to replicate itself onto many machines. If you or your children are loading floppy disks of dubious origin (like a pirate copy of a game) onto the computer, your machine is vulnerable to a virus. Anti-virus software would also be advisable for users who download many program files from an on-line service or the Internet. Downloaded data files can't hurt you, but program files that perform some function can be dangerous.
One of the best ways to buy software is in special bundles. Software resellers will put together CD-ROM packages. If you're looking for business software, companies such as Microsoft and Novell sell ''suites'' of their most-used office programs.
Eventually, you may find you've outgrown the software originally loaded onto your machine. Maybe you've found a new program you want to try. Then it's time to buy a software program and install it yourself.
This is an important step. I remember being afraid the first time I did it. What if something went wrong? What would I do if the screen went blank? Would I damage the machine irreparably?
Such fears proved groundless. It may be reassuring to have your computer buddy on standby. But most installation programs walk you through the process so you can't make a mistake. Even if you do, the worst that can happen is that you turn off the machine and start over again.
* Parts 1 and 2 appeared Aug. 22 and 24; Part 4 will run Monday.