3 ms·
> The punch cards had 80 columns – 72 for the program and 8 for sequencing – so each line of code could be at most 72 characters wide. In case anyone was wonde
by kens 3y ago
> The punch cards had 80 columns – 72 for the program and 8 for sequencing – so each line of code could be at most 72 characters wide.
In case anyone was wondering why the code only used 72 characters, it goes back to FORTRAN, developed on the IBM 701. The IBM 701 was a 36-bit machine. Its card reader loaded 80-column cards one row at a time (sideways to what you might expect), putting the hole pattern in two 36-bit words. Thus, it could only read 72 columns. (A pluggable wiring panel let you select which 72 columns you wanted, but normally it was set to columns 1-72). The 72-character limit has persisted in various places, even though the IBM 701 from 1952 is long gone.
- eyegor 3y agoRiddle me this, where did the magic 132 columns come from? I want to say it was fortran77 when extend source was added to let fortran files use 132 columns.
- kens 3y agoI investigated 132 columns in detail and wrote a blog post about it. It's complicated but essentially, 14 7/8" paper was a standard size going back to the IBM 402 tabulator in 1948, where it was used for 88-column output using a character spacing of 5/32". The IBM 1403 printer (1959) changed to 10 characters per inch, resulting in 132 columns on 14 7/8" paper. https://www.righto.com/2019/01/accounting-machines-ibm-1403-and-why.html https://www.righto.com/2019/01/accounting-machines-ibm-1403-...