The computers are humming in Prince George's high schools in this difficult season of decision. As application deadT lines draw near, seniors must decide whether college days will follow school days. College and university representatives are fanning out across the nation and businesses are searching for recruits.

At Northwestern High School in Hyattsville, as at other county high schools, seniors last week were hunkered down in front of a computer terminal in the guidance center, calling up information on careers and colleges.

"I want to look into a school that will help me into a good law school," said Northwestern senior Wendy Brown as she sat down at the terminal to request information on Tulane University in New Orleans.

At the press of a button, a long list emerged: addresses, telephone numbers, application deadlines, lists of courses, admission requirements and a wealth of other information. Most students live on campus, she was told; it is a requirement for freshmen. Fifty percent of the faculty hold doctorates.

All county high schools have these computer terminals. They are part of a "Guidance Information System" that has 35,000 subscribers throughout the country. Information tapes are changed every six months. Montgomery has used a similar system, with the school district's main computer, for the past three years in five schools on a trial basis. Daryl Laramore, supervisor of counseling for Montgomery schools, said he hopes all schools soon will have guidance computers. But he said he would like a different system because of already heavy demands on the central computer.

The computer is "a good place to start," said Northwestern guidance counselor John Hall. "We have the same information in the books but here they can get a printout and take it home. It's updated twice a year. And a lot more colleges are listed. It really saves time."

"I've used it a lot," said senior Mark Moore. "In the occupational file, it tells you what types of classes you need for particular jobs. You can tell whether you should go for the job. It's really helpful."

Moore asked the computer about a career in welding. He was given a job description, suggestions on useful high school courses, average salaries and a list of states where employment potential was poor. He also was given an address in case he wanted to write for more information.

The computer lists nearly 900 career choices and more than 3,000 colleges and universities. At the Prince George's Career and College Fair last spring, more than 100 institutions were represented.

But the computers are painfully impersonal. Welding, Moore was informed, "involves lifting up to 50 pounds, climbing, balancing, kneeling, stooping, crawling, reaching, handling, feeling, involves talking and hearing, involves ability to see clearly, involves mostly standing."

When it comes to colleges, most students are only browsing. If last year's statistics hold true, only about 40 percent of the county's high school seniors will go to college. Most of those will go to local community colleges or to the University of Maryland. John Hall estimates that half of Northwestern's seniors leave school without plans for the future.

When it comes to personal contact with college representatives, the choice is narrowed further. At the Career and College Fair, no Ivy League institution was represented, said Dorothy Harvey, guidance and counseling supervisor for the county schools. "They're always invited but since they're very selective they don't have to do that much recruiting," she said. "I think it's unfortunate because we do have students who have the capability, and the desire, to investigate some of the more select colleges." Next year, she added, "We're going to make more of an effort to encourage them."

But some organizers of college fairs in the county said "big name" college representatives can be lured with hard work. High Point High School, which is running a fair next week in conjunction with Bowie High, will have representatives from some Ivy League colleges. High Point sent 40 percent of its students to colleges last year, about average for the county, although there was no awesome academic success record to attract the recruiters.

"Last week we had a man from Harvard here," said High Point guidance counselor Dolores Treston. "Several of the Ivy League colleges will be represented at the fair."

Even schools in the south end of the county, which send a slightly lower percentage of students to college than the central and northern areas, manage to attract Ivy League representatives.

Next week the Oxon Hill Public Library, in cooperation with the southern area public schools, is having a "College Convention." Brown, Dartmouth, Harvard, Princeton and Yale will represent the Ivy League, and Bryn Mawr and Vassar will represent the Seven Sisters.

"You have to work hard," said librarian Diana Hirsch. "A lot of it is just keeping track of what's happening." She cites her efforts to persuade Vassar to send a representative. She sent an invitation to the college and was told it would be sent to its Baltimore representative. The Baltimore representative couldn't come, she said. Then she realized the invitation should have gone to the Washington representative. "So I just kept calling the Vassar Club in Washington," Hirsch said. And now a Vassar representative will be there.

Jay Finkelstein, a 1971 Laurel High School graduate who now lives in the District, is Princeton's Prince George's representative. He said he will go to any school in the county that expresses an interest and wants him to come at a time he can make it. "College fairs, even on a one-school basis, are the best means. I wish more schools would do it," he said. "Especially at night."

He said his closest ties as a representative were to the Eleanor Roosevelt High School, the public school in the county with the strongest academic record. He said Princeton was interested in Roosevelt simply because it sent more applications to Princeton than any other county school. A strong success record isn't essential to get a representative to attend, he said: "Roosevelt had its first student accepted to Princeton last year."

But he says many public schools sell themselves short when it comes to applying to highly selective colleges.

"In Ivy League colleges, or all highly selective colleges, they tend to want more information," he said. "The more information that can be provided by the schools, the better the applicant's chances." But in most public schools, he said, "the guidance offices are so overworked that it is difficult for them to provide the detailed information the colleges are looking for." Private schools generally do a better job at this, he said, "probably because the student body is more oriented to selective colleges."