In the 1950s, punched-card equip-ment dominated the commercial computer market. These electromechanical devices could perform the full range of accounting and reporting functions. Because they were programmed by an intricate system of plugboards with a great many plug-in cables,and because care had to be exercised in handling and storing punched cards, only experienced persons were permitted near the equipment. Although any of these individuals could have set up the equipment for fraudulent use, or even engaged in sabotage,apparently few, if any, actually did so.
The punched-card accounting systems typically used four processing steps. As a preliminary, operators would be given a “batch” of documents, typically with an adding machine tape showing one or more “control totals.” The operator keyed the data on each document into a punched card and then added an extra card, the batch control card,which stored the batch totals. Each card consisted of 80 columns, each containing, at most, one character. A complete record of an inventory item, for example, would be contained on a single card. The card was called a unit record, and the machines that processed the cards were called either unit record or punched-card machines. It was from the necessity to squeeze as much data as possible into an 80-character card that the later Year 2000 problem arose. Compressing the year into two characters was a universally used space-saving measure; its consequences 40 years later were not foreseen.
A group of punched cards, also called a “batch,” were commonly held in a metal tray. Sometimes a batch would be rekeyed by a second operator, using a “verify-mode”rather than actually punching new holes in the cards, in order to detect keypunch errors before processing the card deck. Each batch of cards would be processed separately, so the processes were referred to as “batch jobs.”
How Punched Card Works used in computer-
The first step would be to run the batch of cards through a simple program, which would calculate the control totals and compare them with the totals on the batch control card. If the batch totals did not reconcile, the batch was sent back to the keypunch area for rekeying. If the totals reconciled, the deck would be sort-merged with other batches of the same transaction type, for example, the current payroll. When this step was complete, the new batch consisted of a punched card for each employee in employee- number order. The payroll program accepted this input data card deck and processed the cards one by one. Each card was matched up with the corresponding employee’s card in the payroll master deck to calculate the current net pay and itemized deductions and to punch a new payroll master card, including year-to-date totals. The final step was to use the card decks to print payroll checks and management reports. These steps were identical with those used by early, small-scale electronic computers. The only difference was in the speed at which the actual calculations were made. A complete process was still known as a batch job.
With this process, the potential for abuse was great. The machine operator could control every step of the operation. Although the data was punched into cards and verified by others, there was always a keypunch machine nearby for use by the machine operator. Theoretically, that person could punch a new payroll card and a new batch total card to match the change before printing checks and again afterward. The low incidence of reported exploits was due to the controls that discouraged such abuse, and possibly to the pride that machine operators experienced in their jobs.
