A 57-year-old engineer from Olney filed suit in U.S. District Court here today charging that an international computer development firm discriminated against him on the basis of his age.

Lyle W. Mader, who claimed in his suit that Control Data Corp. forcibly retired him two years ago, also charged that "a pattern of age discrimination" existed at a Rockville office of the firm, where Mader worked for 16 years.

Mader, a professional engineer and physicist who holds three patents, helped design magentic components for cmputers and also developed optical reading systems when he worked at Control Data's optical character recognition (OCR) plant formerly located in Rockville. The plant was moved to Minneapolis sometime after Mader was laid off.

He was project manager for the firm's page reading machine, which transforms words on printed pages to electrical signals for computers.

A spokesman for Control Data's headquarters in Minneapolis said he would have no comment until he reviews the case.

However, added James Bowe, vice president of corporate relations, on the basis of the company's employment record "it would surprise me if there is merit to this suit."

In the lawsuit, Mader claimed that in 1974, while Control Data Corp! was in the midst of a poor financial year, he was asked to resign or take a $4,000 cut in his $25,000 annual salary.

Mader said that he consented to the salary cut in order to keep his job and take advantage of a new retirement program that was to begin in 1975.

"They were trying to get me to quit," Mader said in an interview today.

Then in December, 1975, he was laid off and never asked to return to work. Mader alleged that since August of that year at least 10 other persons over 50 years of age were laid off or fired.

In most cases, he stated in his suit, "younger people of the same work category with less seniority" were retained as employees.

Mader subsequently appealed to the U.S. Labor Department which informed him that it could find no evidence of age discrimination.

The layoffs at Washington area Contro Data offices numbered in the hundreds, according to a companu spokesman, and in the thousands worldwide during a period of "terrible financial losses" in 1974-75.

Part of the finacial crunch resulted from Comtrol Data's loss of a production contract for Washington Metro's farecard machines, which the firm had designed and had expected to manufacture.

The Labor Department did find that another Control Data employee laid off from the same plant as Mader at about the same time was discriminated against because of age.

The man, who was in his late 40s, claimed he should have kept his job, which was passed to a coworker 20 years younger and with six years less tenure.