Although computers are becoming almost ubiquitous these days, it's important to remember that in the middle 1970's, a mainframe computer was still pretty rare. Machines were still displayed in secure glass "fishbowls" that mere mortals were rarely allowed to enter. One was forced to deal with the computer indirectly, most often via punch cards and printouts. Magnetic tape was used for long-term machine-readable storage; original card-decks were retained in case you ever needed to revise or resubmit a program. Printouts were bound and retained for later reference.
Users typically prepared their programs on PUNCH CARDS -- nothing more than a perforated piece of stiff paper, 83 mm high by 187 mm long and divided into 80 vertical columns of 12 zones each. Hollerith code was used to represent data on the cards themselves -- internally, the UNIVAC used either ASCII or EBCDIC codes to record a "card image" of eighty characters in length.