A new form of computer input arrived at CRNL with the G-20 computer in the early 1960s – paper punch cards that could be read rapidly by an optical reader. These 8.4 cm by 18.6 cm cards were used both to input programs and data. The input for a single computer run might consist of several thousand of these cards and the greatest fear for all who handled them was dropping one of the boxes containing the cards and somehow shuffling the order in which they needed to be read. Various colours were used to indicate program code or data input as well as the start and end of jobs. At the Whiteshell Laboratories, before a large computer was installed on-site, the cards were read by a reader on-site and the data was transmitted via telephone line to a computer in Winnipeg.
