Re: ALTER, ASSIGN and labels-as-values (was: Unicode in strings)

On Wed, 29 May 2024 04:53:26 -0000 (UTC), Lawrence D'Oliveiro
<ldo@nz.invalid> wrote:

This is why the source code didn’t go beyond column 72: so that the last 8
columns could be used for a sequence number.

The cards were 80 columns wide because this improved on the old 45
column cards, allowing more information to be  stored per card when
used with tab equipment.

Then the IBM 704 computer came along, which had a 36 bit word length.

IBM, in its infinite wisdom, decided that computer users, unlike tab
equipment users, could get by without being able to use the whole
card. So they made their card reader read the card by rows, with the
holes in the first 36 columns going in one word, and the holes in the
next 36 columns going in the next word.

The card readers probably had plugboards in them, so you could choose
a different eight columns to skip if you wanted. This would be handy
if you wanted to port programs written in ALTAC for a Philco 2000
computer.

So when FORTRAN was written, they just put the program in the columns
on the card that the computer could read, and being able to have
sequence numbers was just a happy accident. But it was found to be
sufficiently useful that it was kept in other machines that could and
did read the whole card.

So the sequence number was the effect and not the cause.

John Savard