I'm not going to go into great detail. I expect everyone to read and understand the section.
Simple math is slow and error-prone for humans.
Many devices have been developed throughout history to deal with these problems. Hardware Initially, the solutions were simple mechanical devices - abacus, Napier's bones, knotted string, and the slide rule. Later solutions involved clever and finely crafted machinery. The programs were punch cards. Delicate, inflexible, but stored programs nonetheless.