If you're a regular reader of this column, the term "memory-resident" may be resident in your memory. If not, it's time to freshen the memory, because "memory-resident" is THE hot buzzword in business software right now.

"Memory-resident," you may remember, refers to a software program -- SideKick and ProKey are well-known examples -- that is loaded into RAM memory before it's actually needed; normally, you load in memory-resident programs automatically when you first turn on the computer. The program then sits there until called (usually with one or two keystrokes), at which point it leaps instantly to the screen, right on top of whatever else you were doing on the computer.

It's this instant-access feature that makes "memory-resident" software desirable for desktop utility programs, such as those that turn your computer into an appointment calendar, Rolodex or calculator. If you had to get out a disk and load in one of these programs each time you wanted it, the software wouldn't make sense; it would be simpler just to use an ordinary, low-tech desk calendar. But when the programs are "memory-resident" -- just one keystroke away, no matter what you're up to -- it's much faster and easier to let your computer be your calendar.

The first memory-resident programs, which appeared in early 1984, fell into two categories. There were desktop utilities, like SideKick, with their calculators, calendars, notepads, etc. (As noted here previously, these programs so greatly enhance your daily work that you're nuts if you don't have one.) Then there were the keyboard "Macro" programs, like ProKey, that let you enter a long string of frequently used commands or text with a single key.

The next generation of memory-residents expanded a little on these categories. There were clock programs that flashed the time on your computer screen and rang alarms so you wouldn't miss a meeting. There were "Help" programs like MAXAM, which puts a complete MS-DOS manual in memory, with instructions on any command just a keystroke away.

But this fall has seen a virtual explosion of new memory-resident software. This was an inevitable result of the rapid decrease in the cost of RAM memory chips.

Competition and increased productivity in the chip industry have made RAM memory so cheap that it is virtually free; the difference between a memory board with 256 kilobytes of memory and one with 640 kilobytes is about $40 these days. As a result, today's personal computers tend to have lots of RAM memory, and the software industry, in turn, is pouring out all sorts of new memory-resident programs to reside in those wide-open RAM spaces.

For example, several companies now offer memory-resident spelling checkers. That is, rather than taking the time and trouble to load a dictionary and program to check the spelling in your two-paragraph letter to Mom, you can just hit one key and a memory-resident spelling program goes instantly to work. In a related vein, there are memory-resident thesaurus programs. With these, you put your cursor on a word in the report you're typing, touch "ALT-T," or some such combination, and a thesaurus waiting in memory offers a dozen synonyms for the word at the cursor. Again, the great virtue is that it all happens in the blink of an eye.

Combining both of those functions is the new $100 "Turbo Lightning" memory-resident from Borland International. It is a fast, well-designed program that puts a dictionary and thesaurus literally a keystroke away. But Borland has much greater plans for this Lightning program.

Borland has bought "electronic rights" to a collection of reference books -- Bartlett's Quotations, the Columbia Encyclopedia, Black's Law Dictionary, etc. -- and says it will offer them, too, in memory-resident form along with "Lightning." If this comes to pass, then any personal computer with enough memory and storage -- we're talking a million kilobytes of RAM and a fairly hefty hard disk -- will hold as much information as the reference room in the public library. And all of it retrievable in seconds.

Finally, we're starting to see some standard applications programs -- word processors, spreadsheets, etc. -- coming out in memory-resident form. An impressive example is the $100 program "Ready" from Living Videotext, which is a souped-up version of the same company's "ThinkTank" outlining program. You make an outline or just bang out some notes with "Ready" and then load up your word processor. Your notes and/or outline are always waiting for you in RAM memory, ready to pop up instantly in a window on your screen.

The coming of 1986 will see a flood of additional applications programs coming out in "memory-resident" form. I'll probably buy them all, too; I'm really a sucker for that magic moment when I hit the appropriate key and a whole new program jumps up on the screen.