A veteran journalist will be working in the Pentagon's public affairs office for the first time in more than a year when Fred S. Hoffman becomes deputy assistant secretary of defense for public affairs next week, the Pentagon announced yesterday.

Hoffman, 61, has built a reputation for accuracy and reliability during 24 years on the Pentagon beat for the Associated Press. His files and historical memory are so deep, in fact, that military public affairs officers have been known to call him quietly for information when questions from other reporters leave them stumped.

Hoffman succeeds Kathleen Troia, a speechwriter who held the job for about a year after former New York Times reporter Benjamin E. Welles left the post. He will work for Michael I. Burch, assistant secretary and a retired Air Force officer. RANK HATH REPAIRS . . .

The Army raised some eyebrows not long ago when it spent $514,600 to refurbish the chief of staff's residence at Fort Myer, now occupied by Gen. John A. Wickham Jr. The renovation included $339,186 for a new heating and cooling system, $17,273 for new carpets and $16,438 for drapes.

Rep. W.G. (Bill) Hefner (D-N.C.), chairman of the Appropriations subcommittee on military construction, questioned whether the spending was appropriate, especially in light of chronic problems in family housing for enlisted soldiers.

"It is clear that I can no longer rely on the integrity of the services to report expenditures on the high cost units or to distinguish between maintenance and construction funds," Hefner said in a letter to Defense Secretary Caspar W. Weinberger.

Weinberger responded that the spending was not imprudent. "This is clearly not a case of ranking military officers abusing their authority in order to provide themselves with gracious houses," he wrote.

The Army explained that the chief's residence is a historical landmark built in 1899 that had not been overhauled in decades. In addition, most of the residence, which has 11,700 square feet of space, is used for official functions and guest accommodations, with personal living area occupying only 3,800 square feet. FOUR MORE YEARS? . . .

Weinberger is behaving as if he expects to be holding his job for some time, according to aides. Weinberger, they say, is gearing up enthusiastically for his annual defense of the military budget, scheduling briefing sessions and planning strategy.

This year Weinberger will argue, as usual, that the top line agreed to earlier for fiscal 1986 -- about $334 billion, compared with this year's $293 billion -- should also be the bottom line. If budget cutters in the administration say he should compromise, as they have suggested in the past, Weinberger will note that the number already reflects last year's so-called "Rose Garden compromise" and should not be cut further.

The Pentagon is likely to push hard for funds to manufacture chemical weapons, the one weapon system that Congress rejected during President Reagan's first term. Spending for the MX missile and the "Star Wars" initiative, which the administration will try to increase substantially, also are likely to spark fights. NAME CHANGE . . .

A piece of news that may not have received enough attention when the Army announced it last August: The Materiel Development and Readiness Command, with headquarters in Alexandria, has been renamed the U.S. Army Materiel Command.

Old-timers may remember that when the agency was established in 1962, it was called the U.S. Army Materiel Command. In 1976, it was "redesignated," as the Army says, as the U.S. Army Materiel Development and Readiness Command (known as DARCOM). The Army said the switch back to the original name "is the culmination of five years of examination and organizational change to strengthen the Army's management of materiel." STARS IN THEIR EYES . . .

Reagan has approved a fourth star for Lt. Gen. Robert C. Kingston, who heads the Central Command, the Pentagon announced this week.

The decision upgrades the command, which is responsible for the Persian Gulf region. The Central Command, based at MacDill Air Force Base in Tampa, is the successor to the Rapid Deployment Force.

The promotion brings the command in line with the other unified commands, such as the European Command headed by Gen. Bernard W. Rogers and the Atlantic Command headed by Adm. Wesley L. McDonald. The Southern Command, based in Panama, went from three stars to four stars when Gen. Paul F. Gorman took over.