Once the card was read, where in memory are the 80-columns of data placed, you wonder? In positions 1 through 80, of course. The 1401 mapped the first 333 positions of memory for card input (1-80), card output (101-180), and a print line (201-332). The 333rd position of memory could be used for printer channel control. If you are scheming how to use those leftover positions from 81-100 and 181-200, you are ahead of the game.
08 August 2008
Dan Wohlbruck has started a series of columns on his early days as a programmer in the 1960s, starting with training on the IBM 1401 system. The 1401 used a model 1402 80-column card reader-punch for input and a 1403 printer for output.