The tips of the vacuum tubes in the ENIAC accumulators, which were arranged in 10 x 10 grids, poked through holes in the machine’s front panel. But the faint light from the neon bulbs, which served as indicator lights, was barely visible. So Eckert got Ping-Pong balls, cut them in half, wrote numbers on them, and placed them over the bulbs. As the computer began processing the data, the lights in the room were turned off so that the audience would be awed by the blinking Ping-Pong balls, a spectacle that became a staple of movies and TV shows.
