Census workers using a tabulator machine, U.S.A., 1920

Inside an office, census workers are seen using what will be known as an IBM 100 tabulator punch card machine, U.S.A., 1920. The tabulating machine was an electromechanical machine designed to assist in summarizing information stored on punched cards. Invented by Herman Hollerith, the machine was developed to help process data for the 1890 U.S. Census. Later models were widely used for business applications such as accounting and inventory control. It spawned a class of machines, known as unit record equipment, and the data processing industry.