You are a Latin American politician being held prisoner by a left-wing group. A sympathizer has just passed you a secret message. If you can break the code, you will be able to escape your captors. Hurry, your abductors will return soon! Clue: Cross out the words that are plurals. Coded note follows . . . ."

With this injunction filling the videoscreen, six lively fifth-grade boys enrolled in an introductory course on the BASIC programming language spring into action. Seated in pairs in front of three micro-computers, they pool resources to race the clock.

The information exchange among the young sleuths is frequent, animated and unexpurgated. "Is sheep a plural?" "No, not that button, you turkey, this one!" "Uh oh, you jerk, you crossed out the wrong word." "Hey, how did you guys do that? Can you show us?" "We did it, we did it! We broke the code!" "Now tell us how we can make our own codes."

That's a capsule of what Mary Mullins, an experienced systems analyst, has been teaching children aged eight to 14 after school in Chevy Chase. This summer, she's offering five two- week sessions in LOGO, BASIC and a junior word-processing course.

"What I strive for in my classes is not so much computer literacy as computer comfort," Mullins says. "Computers will be everywhere when today's children reach college age."

More subtly, she adds, "In working with the computer, there's always a second chance to think through a problem, to break it into its component parts, to experiment with an alternative approach. Exploration is the key. Nobody strikes out the first time at bat."

This "try it again" spirit casts her as adviser and helper, the children as initiators. For the most part, they accept the challenge readily.

The classes are small, the children are seated in pairs at the computers, and a team effort is expected. There are no rote drills; no formal lectures; no written handouts. And there's always time at the end of each session to experiment and explore on your own.

Her students come from diverse backgrounds, so Mullins never really knows how a given class will turn out. Each session starts with a selected concept or program. But once the pupils start to work on it, there's no predicting where it will go. Some will finish the problem immediately and move on; others will continue to work the idea out for the duration of the class; others will create their own programs.

The classes have hit only a few snags: For some reason, the enrollment of girls lags significantly behind that of boys. For those girls who do enroll, teaming with boys can sometimes be a problem: "Have you ever tried to get a third- grade girl to work with a third-grade boy?" Mullins asks. "It helps if you can get them to sit closer than 10 feet!" And even with pairings of the same sex, experimentation with the computer can get a little too rambunctious for a classroom setting.

But all in all, the students show tenacity, curiosity and self-confidence as they explore the computer's potential, and theirs.

In a recent LOGO class in which third- and fourth-graders were to create commands and direct the movement of a "turtle" on the videoscreen, most of the students were soon able to "call up" the appropriate sequence by keying in the new command they had just written. After that, they took off in all directions. Two wanted to define other new commands ("Can we use bad words, Mrs. Mullins?") Others returned to their earlier exploration of the graphics capability of the "turtle." ("If I key in circle 500, will it go off the screen?"). Still another poor soul was struggling to recall his "TO GREET" command, which he had keyed in as "TO GREAT." ("The machine says I DON'T KNOW HOW TO GREAT, Mrs. Mullins!") They had to be reminded to leave when class was over, and even then it was difficult to clear the room. The magic of the computers still cast its spell.

GETTING WITH THE PROGRAM -- Mullins' summer program consists of five two-week sessions beginning June 20. The offerings are BASIC programming language and LOGO programming language (each two hours daily, $200), and junior word processing (one hour daily, $100). For information, call Mullins at 537-0226.

Lois Engel is a local writer. COMPUTER PROGRAMS A variety of area schools and day camps also offer summer computer classes. DISTRICT OF COLUMBIA AMERICAN UNIVERSITY -- All-day program for gifted and talented children includes 90-minute computer classes. Two-week sessions begin June 20, July 5 and July 18. $270 to $300. Massachusetts and Nebraska avenues NW. 686-6150. BEAUVOIR SCHOOL -- A four-week all-day program begins June 20 for children eight to 14. $800. 3500 Woodley Road NW. 537-6599. CAPITAL CHILDREN'S MUSEUM -- One-week sessions for ages eight to 12 begin on July 11, August 1 and August 8. $100. 800 Third Street NE. 543-8600. D.C. PUBLIC SCHOOLS -- Classes and camp are available to children selected by their schools. 724-4168. GEORGETOWN DAY SCHOOL -- Three-week sessions begin June 27 and July 18 for children in grades 4 to 12. $150 plus supplies. 4530 MacArthur Boulevard NW. 333-8569. HOWARD UNIVERSITY -- Program for gifted children in grades 2 through 9 begins June 27. $315. Pre-testing required. 636-5633. MARET SCHOOL -- Sessions for grades 7 to 12 begin June 20 and July 11. $200 per session. 3000 Cathedral Avenue NW. 483-5710. ST. ALBAN'S SCHOOL -- Various classes for grades 3 to 12. Three- week sessions begin June 20 and July 8; six-week session begins June 20. $175 to $570. Wisconsin and Massachusetts avenues NW. 537- 6450. SIDWELL FRIENDS -- One-week, three-week and four-week sessions begin June 20. $60 to $200. Lower school, 5100 Edgemoor Lane, Bethesda; upper school, 3825 Wisconsin Avenue NW. 537-8133. TIC -- All-day program with three hours of computer training, three hours of sports. Four two-week sessions begin June 24. $300. Mt. Vernon College, 2100 Foxhall Road NW. 241-5542. MARYLAND BETHESDA-CHEVY CHASE YMCA -- All-day two-week sessions for ages six to 14 begin June 20. $300. 9401 Old Georgetown Road, Bethesda. 530-3725. COMPUTER CONCERNS -- One-week half-day and all-day sessions for ages seven to 18 begin June 20. $120-$185. 19366 Montgomery Village Avenue, Gaithersburg. GOOD COUNSEL -- Three-week morning program for students in grades 7 to 12 begins June 22. $95. 11601 Georgia Avenue, Wheaton. 942-1155. HOLTON ARMS -- Three-week all-day camp sessions for students eight to 15 begin June 20 and July 7. $275. 7303 River Road, Bethesda. 365-5300. LANDON SCHOOL -- Two-week sessions for grades 6 to 12 begin June 20 and July 5. $175. 6101 Wilson Lane, Bethesda. 320-3200. MONTGOMERY COUNTY PUBLIC SCHOOLS -- Programs for grades 4 to 8 begin July 6. $32-$42. 942-8304. PRINCE GEORGE'S COUNTY PUBLIC SCHOOLS -- Programs for ages six to 18 begin June 20. $20 per week. 952-4177. TOWN AND COUNTRY DAY CAMP -- Programs through the summer. 11400 Viers Mills Road, Silver Spring. 949-2345. VIRGINIA ALEXANDRIA PUBLIC SCHOOLS -- Programs for grades 3-6 begin June 23. $50. 998-2122. ARLINGTON CAREER CENTER -- Various programs through the summer. 486-2777. BURGUNDY FARM -- Day-camp program for children eight to 12 including elective computer instruction begins June 20. 3700 Burgundy Road, Alexandria. 960-3431. CHILDREN'S COMPUTER EXPERIENCES -- Six-hour sessions classes at various Chuck E. Cheese Pizza Time Theaters. $35. 960-3313. COMMUNITY COMPUTERS -- Four-week programs for ages 15 to 18 begin June 21 and July 25. $100. 2704 North Pershing Drive, Arlington. 527-4600. COMPUTER EDUCATION INSTITUTE -- One-week classes through the summer. $95. 4300 Evergreen Lane, Annandale. 800/368-3710; in Virginia, 800/572-3434. FAIRFAX COUNTY PUBLIC SCHOOLS -- Summer enrollment is closed. McLEAN COMMUNITY CENTER -- Three two-week all-day sessions with elective on-hour computer classes begin June 27 for ages eight to 12. $100. 1236 Ingleside Av., McLean. 270-9248. ST. STEPHEN'S SCHOOL -- Programs for grades 3 to 12 begin June 20 and July 18. $225. 1000 St. Stephen's Road, Alexandria. 751-2700.