The state of Mississippi and two foundations have linked up to fight one of the country's highest illiteracy rates by putting teaching computers into every public elementary school within four years.

Gov. Ray Mabus said this week that the Riordan Foundation of Los Angeles and the Rord Foundation of New York will make an initial investment of $1.5 million to begin installing computers this fall.He said the foundations would raise an additional $5.5 million over the next three years. He said the state would provide about $1.5 million a year in matching funds.

The computer learning system would be made available to kindergarteners and first-graders in the state's approximately 500 schools.

"We have a goal in Mississippi for everybody to read and write. I think today we are taking a big step in that direction," Mabus said.

Mabus said he hoped to get the computer labs - which include the computer work stations, listening library station and other working areas - in place in about one-third of the state's 150 school districts by this fall.

Mabus and his wife, Julie, have promised to fight illiteracy in the state. Based on 1980 census data, state officials estimate that as many as 400,000 adults in Mississippi have fewer than nine years of formal education and most of them are functionally illiterate. The state's population is 2.3 million.

"Mississippi will be the first state in the country, to our knowledge, to have such an extensive computer literacy system for its children," Mabus said. "Every child in Mississippi should, when this program is in place, leave the first grade knowing how to read and write."

Dick Riordon said his foundation has provided for similar computer learning systems in several California cities, and in Kansas City, Mo., Chicago and New York. But he said this was the foundation's first statewide effort.

The project is to use IBM's "Writing to Read" systems. The computers allow children to write anything they can say and read what they write. It also lets students learn at their own pace.

"If they are slow, it doesn't criticize them," Riordan said.