1" paper tape buy ?

Brent Hilpert hilpert at cs.ubc.ca
Thu Feb 26 16:54:38 CST 2009

Mike Loewen wrote:
> On Thu, 26 Feb 2009, John Floren wrote:
> > I thought 80-column cards were 80 bytes? One byte per column? I've
> > never actually used them, so if somebody could explain to me that
> > would be interesting.
>     There are 80 columns with 12 rows each.  I assumed the worst case of
> using two ASCII characters to represent each byte.  You could punch them
> in binary and get 1 byte in each column with a nibble left over in each
> column.  Or, you could pack 3 nibbles in each column and get 120 bytes,
> but it would play hell with your punches.  :-)

Practically speaking, I wonder if there was a 'good practice' limit on how many
holes could be punched in one column, too many holes and a card might become
flimsy and likely to fold along the column(s), reducing the theoretical maximum
bit density.

The 8-bit EBCDIC punch encoding shown here
still has some holes in the value-space (punch patterns for all 256 values are
not shown), although it could reasonably be expanded to achieve 256 values.

Was there a standard 8-bit binary punch pattern (to get a full 8-bit byte out
of one 12-bit column)?

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