In three free workshops coming up this month, computer users can brush up on their computing skills at the Alameda Main Library, 1550 Oak St. The classes will focus on the Windows operating system and how to integrate it with portable devices. The first class takes place Wednesday, March 13; register at the circulation desk. Above, replacing a bad tube meant checking among the ENIAC computer’s 19,000 possibilities. The forerunner of today’s personal computers was introduced in 1946.