Despite a fourth-quarter slowdown, Hechinger Co. sales topped the $200 million mark for the first time last year and profits jumped 26 percent, the Washington do-it-yourself home-center chain reported yesterday.

Hechinger officials described the gains as "significantly better than those of most retailers during this period of high unemployment and economic uncertainty."

Hechinger earnings climbed to $8.6 million ($1.17 a share) from $6.8 million ($1.03) for the year, while sales increased 24 percent from $170.4 million to $210.6 million for the 12 months ended Jan. 30.

The rate of gain slowed somewhat in the final three months of the fiscal year, however, with sales increasing 12 percent to $46.6 million from $41.6 million and profits moving up to $2.4 million (33 cents) from $2.1 million (31 cents).

Roughly half the sales gain came from opening new stores, but sales of existing Hechinger outlets were up 12 percent for the year and 3 percent in the fourth quarter.

The chain will open its newest store April 24 at Security Square Mall in Baltimore County, then plans to add its third store in the Philadelphia market and a new unit at Dobbin Road Shopping Center in Columbia later this year.

Systematics General Corp. earned its first quarterly profit in 15 months, but ended the year with a loss of $1.18 million (86 cents) on sales of $12.2 million, compared with a profit of $611,000 (44 cents) on $11.3 million worth of business in 1980.

Systematics reported net income of $23,000 (2 cents) on sales of just over $3 million for the three months ended Dec. 31, compared with a loss of $2,000 (one cent) on volume of $2.9 million for the same period of 1980.

The Sterling-based computer engineering, services and equipment firm said the turnaround was "the result of restructured manufacturing operations and a 30 percent increase in systems engineering and services work."

Arundel Corp., the Baltimore-based building conglomerate that was forced to cut back its operations last year, reported it cut in half its loss for the year and said continuing operations turned a small profit.

The company posed a net loss of $3.4 million ($1.95 a share) for the year compared with a deficit of $7.4 million ($4.22) in 1980. Arundel attributed the loss to the shutdown of its construction division and the sale of the company's interest in four California projects.

Arundel said it earned a profit of $185,000 (8 cents) on continuing operations totaling $53.8 million, compared with a loss of $823,000 (49 cents) on $51.9 million on those operations a year earlier.

For the fourth quarter, Arundel's revenues slipped to $14 million from $14.9 million producing a loss of $1.1 million (62 cents) compared with a profit of $1.3 million in the same period a year earlier.