High interest rates and foreign exchange problems depressed Black & Decker Manufacturing Co. earnings by 97 percent in its fourth quarter and 27 percent for the year ended Sept. 27.

The Towson-based hand-tool maker posted fourth-quarter earnings of $681,000 (2 cents a share), down from $19.56 million (46 cents) for the same period last year. Sales for the quarter totaled $312.07 million, down 4 percent from 1980. The 1981 earnings reflect a 43-cent-a-share reduction because of foreign-currency effects compared with a 2-cent reduction in 1980, the firm said.

Earnings for the full year declined to $65.7 million ($1.56) from $90.1 million ($2.14) in 1980. Sales fell just one percent, to $1.431 million in 1981 from $1.438 million in 1980.

Improved earnings were reported by C3 Inc., a Reston microcomputer company. Profits for the second quarter ended Sept. 30 climbed to $2 million (23 cents a share) from $1.1 million (16 cents) in the same period a year ago, as revenues jumped to $11.3 million from $7.3 million.

For the first half of its fiscal year, C3 earned $3.8 million (44 cents) on revenues of $21.9 million compared with profits of $2.2 million (31 cents) on revenues of $14 million in the first half of 1980.

Survival Technology Inc. of Bethesda has announced earnings for the fourth quarter and the year ended July 31. For the quarter, profits increased to $394,000 (16 cents a share) from a loss of $149,000 in the fourth quarter of 1980.

For the year, the medical devices and services firm posted earnings 35 percent above 1980, rising to $883,600 (35 cents) from $652,600 (26 cents).

The firm attributed its financial improvements to cost-reduction programs and productivity-improvement measures.