Federal agencies are busy trying to figure how to live with - or duck - the presidential directive that says that no government worker can be fired because his or her agency is reorganizing.

In the battle of semantics and legal interpretation, some agencies will try to push ahead with plans to fire substantial numbers of workers as part of reorganization programs already set in motion by Cabinet officers and agency heads.

Although the big Carter reorganizations won't come until next year - Congress willing - half a dozen federal units already we rearranging manning tables, organizational charts and planning to move or eliminate various jobs.

The Office of Management and Budget and the Civil Service Commission sent agency heads a three-page directive yesterday spelling out the President's desire that nobody in government would be "adversely affected" by reorganization.

It includes a presidential promise to push for legislation to restore most federal workers who have been downgraded this year to their old pay and grade level, and advises agencies that employees cannot be fired because of reorganization unless a valid job offer "preferably at the same grade" level is made to them, and they refuse.

Several federal agencies, including the CIA, Defense headquarters, Agency for International Development and Housing and Urban Development either are cutting jobs, or plan to because of reorganizations of one sort or another. Both Defense and the CIA have been careful not to use the term "reorganization" in discussing their job cutback plans.

At the moment, it appears that both the CIA and the Office of the Secretary of Defense believe they are exempt from the President's pledge. But they are checking to be sure.

CIA plans to fire more than 800 senior Washington workers because of a change in mission. That reduction - reliance on satellites rather than human operatives - might escape the nobody-gets-hurt order which exempts agencies undergoing "program and budgetary adjustments . . . (and) office closings or other reductions for efficiency."

The OSD has ordered a 25 per cent cutback in headquarters jobs, a move that originally hit 782 civilian and military jobs. Now, Defense officials say, it looks as though fewer than 65 people will be fired by Jan. 6, the date of layoff notices. That number could drop even more if additional employees retire or find other jobs.

HUD, which is undergoing a major reorganization in the field, has contemplated firing and/or transferring several hundred workers (some coming back to Washington). HUD, like some other agencies, has frozen hiring. Yesterday it presented a plan for "consultation" about the reorganization to the presidents of the American Federation of Government Employees and the National Federation of Federal Employees. Both unions represent HUD workers in the field. The consolidations planned could affect the union's representation rights - as well as cost members' jobs.

Meantime, the Office of Management and Budget and Civil Service Commission say they will keep close tabs on agencies to make sure that they observe both the letter and the spirit of the Carter directive. OMB in particular takes a dim view of agencies that call reorganizations by another name in an attempt to skirt the presidential promise.

Insiders say that acting OMB director James T. McIntyre Jr. worked very hard to get the presidential promise into a workable form that agencies could understand and adhere to. The word is that OMB, which controls budget requests, will be very tough on agencies that try to fudge on the president's nobody-gets-hurt-pledge. CSC Chairman Alan K. Campbell, the chief administration salesman for reorganization, also is very eager to keep the bureaucracy - which is nervous over reorganization - as calm as possible.

Campbell presided at an afternoon meeting Wednesday of the Interagency Advisory Group. The TAG is made up of most of the government's personel directors. Word is that they got copies of the OMB-CSC guidelines, and a reminder from Campbell that they represent the President's thinking.