In a typical display of corporate and government cooperation, Japan is engaged in a determined search for the technological breakthrough that could make it the world's leader in the coming era of giant computers.

Financed in part by a comfortable government subsidy, five Japanese companies have pooled their research talent in an expensive race for the key to making large computers marketable in the 1980s.

If they succeed, Japan's manufacturers would be in a position to challenge the worldwide domination of IBM. So far, the scientists are publicly cautious in their expectations, but prospective competitors are worried.

"When this whole country gets behind something, it usually does what it sets out to do," said one foreign businessman familiar with the high stakes involved.

The secret is to develop the very large-scale integrated (VLSI) circuitry which will enable the next generation of computers to perform millions of functions instantly and economically. IBM is believed to be hard at work, aiming, like the Japanese, for the same vast proliferation of computer work in banking, credit sales, postal work and other fields.

Many observers see in the Japanese effort the same patterns of concentrated research and development that produced from scratch two decades ago this country's formidable steel industry.

The Japanese formula goes something like this: harness industry and government for a specific product; import the basic technology from abroad; refine it and adopt it through domestic research to reach a higher quality and lower costs. And sell, sell, sell.

All of this is geared to the marketplace and the prospect of early commercial success. Relatively little technological research in Japan is for long-range, noncommercial purposes.

This philosophy was summarized recently by Atsuyoshi Ouchi, senior vice president and director of one of the computer corporations involved, Nippon Electric Co., Ltd.

"Our tactic is to stay half a step ahead of the rest of the industry in technology," he said. "One full step is too far ahead, because the market may not be mature and the investment involved is too large and the risk is too great. But we can't win being behind. So we stay half a step ahead."

That formula has propelled Japan to the leadership in exports of manufactured goods. It took American steel-making technology and then fashioned automated plants so high in productivity that they can out-sell manufacturers in many parts of the world. It took transistors and digital technology, added automation and superior quality control, and transformed those innovations into profitable exports.

Video tape recorders were first developed in the United States in the 1950s. But the two corporate giants competing for dominance in that field today, are Japanese, Sony and Matsushita.

"It is still true that Japan is not an innovator technologically," a well-informed American source said recently. "In some of the fields where they have become famous, they obtained the technology from the United States by buying patents or making licensing agreements." What the Japanese added, often with government assistance, were improved manufacturing processes -- the quality control and automation that makes goods marketable abroad.

That is the route being followed today in Japan's computer industry. So far, the companies have been relatively successful in holding their domestic market against American competitors. IBM and other foreign companies have only about 45 per-cent of Japan's market, a much lower share than in other countries.

But Japan has not been able to obtain the export advantage in computers that it has in electronics and digital manufacture. The best available statistics indicate that its companies hold only about four per cent of the world market outside of Japan.

It was this shortcoming in exports that the Japanese government set out to change several years ago when the powerful Ministry of International Trade and Industry (MITI) decided that in the 1980s domestically-made computers should become market leaders around the world.

Japan saw then that its strong grasp of electronic exports would be challenged by low-wage countries, such as South Korea and Taiwan. To MITI, computers seemed the type of "knowledge-intensive" industry at which Japan should excel. About the same time IBM announced it would develop its new "future system," aiming toward the fourth-generation of computers for the 1980s.

Acting in its frequent role of midwife to private companies, MITI assembled Fujitsu, NEC, and other large manufacturers in what is called the Cooperative Laboratory. VLSI Technology Research Association, and gave them a subsidy of $125 million in interest-free loans to develop the new technology jointly by 1979. Later they market the results independently.

Much of the basic technology had been purchased in the United States over the years and the rudiments of VLSI circuitry are common knowledge around the world. The trick is to develop a way of perfecting it for commercial purposes and that is what the Cooperative Laboratory in Kawasaki, an industrial suburb south of Tokyo, has set out to do.

The secret of large computers is the ability to etch large numbers of microscopic circuits, called "bits," on the small chips of silicon that are the heart of modern computers. The largest commercially successful computers today are based on chips with about 16,000 "bits" etched on them by a photo-light process. Fujitsu has developed an experimental model using up to 65,000 bits, now thought to be the maximum by that process.

The Japanese -- and presumably also IBM -- have embarked on lab research using electron beams that would make possible the etching of hundreds of thousands, perhaps a million, or more. By one authority's estimate, that would permit production of computers about 100 times as powerful as the largest IBM model now on the market.