In Pictures: ENIAC, world's first digital computer, turns 66

With Remington Rand the inventors helped develop the first UNIVAC computer, which was delivered to the Census Bureau in June 1951. Unlike the ENIAC, the UNIVAC processed each digit serially. But its much higher design speed permitted it to add two 10-digit numbers at a rate of almost 100,000 additions per second. Internally, the UNIVAC operated at a clock frequency of 2.25 MHz, which was no mean feat for vacuum tube circuits, according to the University of Pennsylvania.