By this reckoning ENIAC and the tabulating equipment which preceded it were first generation systems--set up to solve specific problems by specialists with detailed and precise knowledge of the operation of the hardware. Many of the popular images of computers in the 1950s, seen in cartoons from the period, of the computer stretching from floor to ceiling and covered with knobs, dials, and oscilloscope screens, attended by mad scientists derive from the reality of first generation operation.
In the first generation, the user went one-on-one with the computer, in the computer room, operating the computer at the switch and knob level. Since the user was the operator of the machine and controlled it with little or no abstraction, there was essentially no mediation between the computer and its expert user.