It was in the 1940s, however, that the first electronic, digital computers started to appear -- that is, computers as we know them today. These computers were massive machines, filling a large room (in some cases, a whole building) and yet having less computing power than a simple calculator does today. Reprogramming them often required extensive amounts of physical rewiring, as the only way the computer knew what to do was by how it was connected together.
In the 60's practically overnight the size of a computer was changed enormously, the wires and tubes replaced with the transistor, and replacing the vacuum tubes. By the start of the 70's, it was possible to make computers small enough for people to have in their homes. This is generally regarded as being the beginning of the 'computer age', as the popularity of home computers quickly drove prices down and made them very affordable.