A computer program listing from the 1970s. Before computers had screens, paper printouts were the only way to correct and adapt programs to new requirements. A program was developed in a series of iterations and printed on continuous form paper with green and white ›zebra‹ stripes. Copyright: ArnoldReinhold, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons