General Dynamics Corp., which spent the last month of 1985 under a government suspension barring it from obtaining federal contracts, reported lower fourth-quarter earnings and nearly flat full-year income for last year compared with 1984.

The giant contractor, suspended from Dec. 3 to Feb. 7 because it was indicted for contract fraud under which it allegedly overbilled the Army for billions of dollars, posted fourth-quarter net income of $90.4 million ($2.13 a share), down 15 percent from $106 million ($2.37) in the final 1984 period. Revenue in the latest quarter was $2.3 billion, up from $2 billion in 1984.

For the year, General Dynamics said it earned $383.3 million ($9.05), only slightly above the $381.7 million ($8.08) recorded in 1984. Per-share earnings increased in 1985 because average shares outstanding fell to 42.4 million from 47.2 million in 1984. The company said its revenue rose to $8.2 billion last year from $7.5 billion.

General Dynamics makes the Army's M1 tank, the Navy's Trident submarine, Tomahawk cruise missiles, the National Aeronautics and Space Administration's Atlas and Centaur rockets, and the Air Force's F16 fighter plane.

*Control Data Corp., a maker of large business computers and computer peripheral equipment, experienced a record annual loss for 1985 of $562.7 million, the company said yesterday.

The company, based in Minneapolis, reported its computer operations had a loss of $267.5 million during the fourth quarter.

Analysts, who expected the large loss, said the company's Commercial Credit financial services subsidiary should have provided support for the company's computer operations, but it also had a loss of $4.8 million in 1985 compared with an $82 million gain in 1984.

Control Data revenue for 1985 was $3.67 billion compared with $3.69 billion in 1984.

*ITT Corp. yesterday said it registered a $15 million loss in the fourth quarter of 1985, during which it established a $160 million reserve fund.

The fund included $105 million for the closedown of ITT's project to adapt its System 12 digital switch for the United States and $55 million for the disposal of its message terminal rental and facsimile transmission business.

In the fourth quarter of 1984, ITT recorded net income of $175 million ( $1.16 a share).

The company said its total income for 1985 was $294 million ($1.89), down from $448 million in 1984. Without the fourth-quarter special charge, its annual income would have been $454 million, a $6 million increase.