But the magnitude and the suddenness of the loss surprised and puzzled analysts. An after-tax loss of $100 million in the second quarter for the company as a whole translates into a pretax loss on home computers alone of $200 million to $250 million.

Texas Instruments officials last week declined to be interviewed. ''Not a chance. Absolutely not a chance,'' said company spokesman Norman Neureiter. Indeed, even the home computer division's public relations manager, whose job it is to talk to the press about that specific T.I. activity, has not been allowed to talk to some publications in the last few weeks.

Nevertheless, it is evident that the loss was the result of a combination of factors, all of which are evidence of a consistent problem that T.I. has had in the consumer electronics business. In digital watches and calculators, T.I. helped drive prices so low that it ruined the business, even for itself.

One of the other companies severely hurt in the calculator wars was Commodore International, which was dependent on other companies for the chips it used and was therefore limited in how much it could cut costs. Since then, Commodore has vertically integrated. When Commodore and T.I. faced off again in home computers, Commodore was the winner. Mistake number one for T.I., analysts and competitors say, was getting into a price war with a more agile, lower-cost producer.

T.I.'s home computer was first introduced in 1979 for $1,150 and was an embarrassing failure. T.I. discovered in 1982 that it could sell large volumes by cutting the price and offering rebates. But the T.I. 99/4A, which was little different from the machine that was originally designed to sell for $1,150, was no match cost-wise for Commodore's VIC-20. As Commodore and T.I. started their downhill race, it was inevitable that prices would get so low that T.I. would start losing money while Commodore stayed profitable. T.I. ''got suckered by Jack,'' said Harry Fox, president of Spectravideo, a new home computer company, referring to Commodore president Jack Tramiel.

Even that would not have been too bad had T.I. been able to make up for low-priced computers by making large profits on software and peripheral equipment as it had hoped. But there is a flaw in such a razor-and-blade approach to profits in the home computer market.

The history of the personal computer business, brief as it is, has shown that the successful machines are the ones that have the most and best software available for them. It has also shown that no single company can write all the software itself. It must take advantage of the cottage industry of programmers.