Will computers squeeze out books by 1990?

What will happen to our memory, now that we can keep it on paper?'' the Egyptian Pharaoh Ramses supposedly asked Thoth, the inventor of writing. At least, this is a story Plato told.

In the intervening millenniums, human memories may have suffered some, first as a result of writing and then because of printing. But, in exchange, the printed word has added immeasurably to the breadth and depth of human culture. In fact, modern civilization would not exist without the underpinning of paper and ink.

Today, however, some people are raising a question similar to that of Ramses. In this case, the invention is the computer. And the question is, ''What will happen to the printed word, now that computers are becoming commonplace?''

Some zealous pro-computer prophets are calling this the twilight of the era of print. For instance, Christopher Evans, in the book ''Micro Millennium,'' states: ''The book has been such a long-loved and useful companion to mankind that one should not speak lightly of its decline and ultimate disappearance. Nevertheless there are a number of reasons why this is imminent.''

Evans goes on to argue that computers will totally outstrip the traditional book by the end of the decade, because they will possess several key advantages:

* They will soon be able to store a whole library in a space the size of a book.

* Computer chips containing the text of a book will cost 20 cents to produce.

* Computer books will be dynamic, rather than passive, sorting and processing text in various ways impossible with the printed word.

As persuasive as some of these arguments seem, they may be overly facile. Some important differences between reading on a computer monitor and reading in a book are not taken into account. And many people within the publishing industry are highly critical of such prognostications.

One such is Barry Richman. He is a man with one foot in the computer industry and the other in the world of books. An engineer turned book editor, he is general manager of Osborne/McGraw-Hill, a publisher of computer books.

''I love both books and computers, but there is a functional difference between the two media,'' Mr. Richman says. ''The electronic media is most engaging for dynamic processes - writing, for instance. But for reading, print is much more accessible.''

Noted mystery writer John D. MacDonald also objects to giving the book its last rites prematurely. In a recent article on the subject, he argues that books ''will be books just as before, for a long time to come.''

For some reason, people have difficulty concentrating for long periods of time on text that scrolls down a TV TV screen. Perhaps this is why use of large computers in business and government generally has been accompanied by an increase in the consumption of paper, rather than a decrease. This drawback might be alleviated by the development of a new computer display technology. But a more readable computer screen has yet to put in an appearance.

Thus, even if the advances in computer technology which Evans predicts do take place, there still may be a place for the book beyond the year 1990. One thing is clear, however: Even if computers aren't going to replace books, they are revolutionizing the way words are printed.

Today, an increasing number of authors, like Mr. MacDonald, are writing on computer word processors. Other well-known writers who have foresaken the pen and typewriter include science-fiction writer Arthur C. Clarke and novelist Stanley Elkin. A few publishers are already accepting manuscripts on computer disks.

Naturally enough, such publishers of computer titles as Osborne/McGraw-Hill have moved farthest along in this process. Osborne has developed equipment that allows the company to accept manuscripts on diskettes from 50 different computers.

Once the manuscript is transferred electronically into the Osborne computer, a printout is made so editors can make changes with pencil. They do it this way rather than electronically for two reasons, explains production manager Paul Butzler: The editors prefer working from printed copies, and a paper copy allows the company to keep an ''audit trail of editorial changes'' - in other words, to have a record of who made which changes, something that is hard to do in computerized systems.

After a manuscript has been thoroughly edited, the changes are made in the electronic copy. Then it goes to the typesetters. Here, codes indicating the size and type of print, width of printed columns, and other typographical necessities are added. The computers then produce ''cold type'' - finished type printed on heavy paper, which is cut and pasted onto pages. Artwork is added, and the pages are photographed. The film is then used in a photo-etching process that makes metal plates, from which the book is printed.

''This is better in every way,'' explains Cheryl Creager, chief typesetter at Osborne. ''We can pay more attention to making the book look really good.'' Computers have more than doubled the speed at which books can be typeset, and, by putting different formats under single keys, the number of typesetting errors has been slashed significantly.

Mr. Richman enumerates the advantages: ''The cost is a complete wash. What we're getting is speed. Speed is incredibly enhanced. We also gain the leeway to produce quality.''

It is difficult to estimate how rapidly these methods will spread throughout the publishing industry. So far, publishers have not exactly raced to embrace the new technology.

Says novelist MacDonald, ''If you would be thrilled by watching the galloping advance of a major glacier, you would be out of your mind watching changes in publishing.''

According the Richman, there is a reason for what he terms an ''underground resistance'' in the publishing industry.

In the 1960s, publishers were approached by computer salesmen.

They responded eagerly and bought computer equipment that they were told would revolutionize their business. But it didn't work well.

A number of people in senior positions today were badly burned. Now they are cautious.

Yet, however slowly, the publishing industry is responding to the new technology. The Association of American Publishers, for instance, has a project under way to establish a set of standards for writers who use computers. Within the next few years most of the major publishing houses are expected to have the capability to accept manuscripts in electronic form.

It is also clear that this is just the beginning of the transformation of publishing. Sybex, another heavily automated publisher of computer books, will soon be replacing standard techniques of illustration with computer-graphics systems. And at Osborne, Mr. Butzler is investigating the equipment necessary to bypass the photographic steps entirely by burning printing plates directly from disk. The latest Montgomery Ward catalog was done in this fashion, and it eliminates half the production costs, he says.

Further in the future, advanced-laser printers are likely to replace the printing press entirely. One small Illinois publisher is using such a printer to turn out on demand copies of a book on technology consultants. The printer is so fast it produces the 124-page book in a minute. Similarly, a company in New York's Wall Street district offers a laser-printing service that turns out high-quality printed material in 24 hours, rather than the standard week.