3 ms·
Many of IBM's early mainframes could only read 72 columns from a punch card, which is why Fortran (and I assume COBOL) only used 72 columns. Specifically, the I
by kens 6y ago
Many of IBM's early mainframes could only read 72 columns from a punch card, which is why Fortran (and I assume COBOL) only used 72 columns. Specifically, the IBM 704 was a 36-bit machine and read punch cards one row at a time, filling two 36-bit words. There was a wiring panel that let you select any 72 columns to read, but obviously using the first 72 columns was most sensible.
If you punched sequence numbers in the ignored columns 73-80, you could use an electromechanical card sorter to put the cards back in order if you dropped them.
- fortran77 6y ago> if you dropped them. Or if someone shuffled them (as we used to do in the computer room to people who annoyed us.)
- praptak 6y agoMy professor told us of a technique he used to recover from stack drops. Draw a pattern with a felt tip pen across the side of the stack (on the edges of the cards). This way a quick glance can tell you if the stack is out of order and it's also faster to sort manually.