26 Feb
2009
26 Feb
'09
2:54 p.m.
Mike Loewen wrote:
On Thu, 26 Feb 2009, John Floren wrote:
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
http://www.cs.uiowa.edu/~jones/cards/codes.html
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)?
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. :-)