Hoping to attract more novice computer users, both International Business Machines Corp. and Apple Computer Inc. are beefing up their lower-cost personal computer offerings.

IBM said its two-month-old line of home computers became available nationwide yesterday. The firm had launched the Personal System/1 line in June in just three metropolitan areas: Chicago, Dallas-Fort Worth and Minneapolis-St. Paul.

Meanwhile, Apple Computer is gearing up to introduce three new computers in October.

In an effort to blunt criticism of its high prices and to stimulate sluggish sales, Apple is expected to introduce the so-called Mac Classic, which reportedly will sell for less than $1,500, compared to today's lowest-priced Mac at $1,799.

IBM, whose PS/1 line begins at $999, said it will promote the PS/1 nationwide rollout with television and magazine advertisements featuring the theme "IBM Brings It All Home."

The computers will be sold at more than 800 Sears stores, 32 Dayton-Hudson and 62 Dillard's department stores, as well as at selected IBM-authorized dealers.

Selling its products at general retailers represents a strategy change for the world's largest computer company, which previously only sold its machines at computer stores.

James A. Cannavino, IBM's vice president in charge of the home computer line, said the two-month kickoff in the three metropolitan areas "exceeded our expectations."

Another executive, Tony Santelli, said IBM had sold fewer than 10,000 machines.

IBM said that the PS/1 machines are finding a broader audience than expected among both advanced and first-time computer users.

Half of the customers interviewed by IBM bought the machine for running a small business or bringing home work from the office, Santelli said. Three out of four buyers were first-time home computer owners.

Also, buyers have shown greater-than-expected preference for the top-of-the-line PS/1 model, which has a list price of $1,999.

Eight out of 10 buyers so far chose that model, which includes a color screen and a hard disc drive, a type of memory device with a large capacity.

Among the accessories IBM announced for the computers is a printer that it said offers letter-quality printing and four typefaces for $499.

IBM also announced a device that allows users to hook up an electronic keyboard to the computers. IBM said the device will allow users to compose music much the way they work with words on the machines.

This is IBM's second attempt at a low-priced computer tailored for home use.

Its first, the PCjr, failed to catch on and IBM halted production of the machines about a year and a half after their introduction in 1983.

Besides the Mac Classic, Apple will introduce two other higher-priced computers, according to reports in trade journals.

The Mac L will be the lowest-cost Macintosh with a color display, and the Mac IIsi will be aimed at users who want more power.

Although the machines will be unveiled in October, some models may not be available in time for the Christmas selling season.