Former General Electric Co. executive Anthony L. Craig will succeed Joe M. Henson as president and chief executive officer of Prime Computer Inc. after a transition of a few months, Prime said Tuesday. The company also said its board of directors has approved a stockholder rights plan aimed at thwarting any hostile takeover attempt. Henson, 55, has been chief executive of the Natick-based computer maker since November 1981. Company officials described his departure as amicable, voluntary and expected, saying he had informed the board privately last year of his intention to leave. Craig, 43, has been president of GE's Information Services Division. He is stepping in immediately as Prime's chief operating officer, executive vice president and a member of the board. After a transition of a few months, he will assume Henson's posts, according to Prime spokesman Richard Eckel. Henson said he had no personal plans except to take a long vacation and possibly to pursue interests in government and community service. Prime has been facing some problems and has not been immune to the uncertainties affecting the industry as a whole. Prime's profits rose 38 percent to a record $64.8 million in 1987, but the company stumbled this year when aggressive pricing by its competitors forced it to pull out of the mini-supercomputer market and take a $5 million charge against earnings. In addition, Prime's $435 million takeover of Computervision Corp. in February has brought pressure from Wall Street to reduce operating costs. Henson announced in May that Prime would eliminate 700 jobs _ about 5 percent of its worldwide workforce of 13,000 _ through attrition and layoffs. Prime also has been caught in an awkward position in the industry-wide battle between AT&T's UNIX software and a new software standard under development by a coalition of rival computer makers, including International Business Machines Inc. and Digital Equipment Corp. Prime's products are built around the existing UNIX standard, and Henson termed the industry battle unfortunate. ``I'm hopeful that the industry will resolve this debate before long,'' he said. ``Today, clearly, our products support the only available Unix standard, which is AT&T's system 5. But we have expressed an interest in supporting a unified industry standard. What we don't want to see happen is a fragmentation.'' Craig did not signal any major changes in corporate direction. He said he would continue to pursue Prime's current strategy, which he defined as ``focusing on integrated solutions that deal not just with hardware, but go beyond that to the applications...and deal with the support, the design, the training of personnel ... to bring more value to our customers.'' Craig has been president of GE's information services business since September 1986. He joined that division in 1983 as vice president of international sales after 17 years as a product manager and marketing executive for IBM. Taking over Computervision, which is based in Bedford, Mass., has made Prime second only to IBM in the market for computer-aided design and manufacturing systems. Prime is projecting revenue this year of $1.6 billion, up from $961 million last year, with much of the increase resulting from the Computervision merger. Computervision reported earnings of $19.4 million on revenue of $564 million in 1987. Prime reported earnings of $21.7 million on revenue of $772.1 million for the first six months of this year. Prime said its new takeover defense would provide stockholders rights to purchase additional shares in the event of a hostile takeover. A dividend of one purchase right was declared for each outstanding share of common stock, payable to stockholders of record on Oct. 18.