SSEC Program Card

Photo: [83]. CLICK TO ENLARGE.

Fig 8: Numbers that enter into computations and those that direct the operation of the Calculator are read from punched cards.

The card shown is part of a program for calculating a (mathematical or astronomical) table. All instructions are given in numerical form, punched onto cards such as the one shown; this allows the machine to mix instructions with numerical data in its memory, to modify instructions, and so on. Each line of instruction carries with it a number telling the machine where look (in memory) for its next instruction. At any one time, a new sequence can be started at any one of about 200 places. Any given sequence can be repeated a prescribed number of times or until a given result is derived. This facility is reflected in the title "Selective Sequence." [83]. The SIN table referenced is most likely Herb Grosch's sine/cosine table from SSEC Opening Day, and the card might be from the Moon orbit program deck [59].

Frank da Cruz / / Columbia University Computing History / Sep 2003