The sequence field was often left blank on manually keypunched cards,
but was almost always filled with some combination of a "deck" ID and
a sequence number on machine-punched decks, as were "binary" decks.
I remember many times using an IBM 82 card sorter to restore order
to a deck containing gravity-induced entropy. ;-)
There is an interesting historical reason for the FORTRAN compiler
to ignore columns 73-80. FORTRAN was first implemented on the IBM 704
computer, and that machine and its successors, the 709, 7090, 7040,
and 7094, all used a binary card console card reader that read in
"row binary". Since these machines had 36-bit words, the standard
binary card format was 12 pairs of 36-bit words, read from successive
rows of the card, and therefore covering only the first 72 columns.
As a result, the computer could not read columns 73-80 from the console
card reader, and those columns were already conventionally used for
deck sequence numbers. FORTRAN merely continued that convention.
And, of course, what the computer could not read, the compiler must
ignore. ;-)
For example, see:
www.atkielski.com/PDF/data/fortran.pdf
-michael
Parallel computing for 8-bit Apple II's!
Home page: http://members.aol.com/MJMahon/
"The wastebasket is our most important design
tool--and it is seriously underused."