The ENIAC (invented at the University of Pennsylvania) and the ABC (short for Atanasoff-Berry Computer) were the first digital computers. However the next big step were stored program computers like the EDSAC (invented at the University of Cambridge, England). The EDSAC was the first computer to run a graphical computer game, named OXO (or Noughts & Crosses).
A lot of effort just to play Tic-Tac-Toe, right? But Alexander Douglas had bigger things in mind: the game was a part of his thesis about human-computer-interaction. That made Douglas one of the first experts of Usability Engineering :-)