It will be much harder to get a federal job after next Wednesday, when a limited hiring freeze will be slapped on most governmental operations.

President Carter (as The Washington Post reported yesterday) will go on national television Tuesday night to announce his new wage and price guidelines program, designed to cut the inflation rate. The President will outline government plans to lead the way by imposing restrictions on new employment.

Insiders say the freeze probably will take the form of an order to agencies allowing them to fill only three of every four vacanies. Job candidates whose applications already have been appproved will not be affected by the freeze. But people with less than solid commitments could find their hiring barred or delayed.

Federal agencies have been anticipating a freeze for several months and hiring has been up in most departments as managers moved quickly to get people on the payroll. Even so, officials say the government still has about 30,000 unfilled jobs. Many of them - as well as new vacanies - will be caught up in the partial freeze.

Several other actions are in the works that would have the effect of slowing government hiring, and producing gradual reductions in the number of federal jobs.As reported here Sept. 27, the president's new budget to Congress will call for a cut of around 2 to 2.5 percent in employment, or about 38,000 jobs.

The so-called Leach amendment to the civil service reform bill mandates reductions - through attrition. Originally the Leach measure anticipated a cutback of around 100,000 jobs. But the net effect of it, officials say, will be a reduction of around 30,000.

Some federal officials predict that the attrition rate being counted on to help reduce employment will drop when the freeze is formally announced. They based that on experience. Whenever government announces a freeze in its own hiring, federal employes contemplating leaving or retiring tend to stay on longer.

Whatever the result of the freeze, it certainly will make it harder for the average person to get a government job. It also could slow down promotions.