In 1928, American company IBM redesigned the punch card to have 80 columns of 12 potential holes. A light shone on each card as it was fed into the computer. If there was no hole, the light was blocked and the machine read in a 0. If there was a hole, the light shone through and was detected by an optical sensor and the machine read in a 1. Each column of potential holes therefore became a 10-digit binary number.