At 16:57 -0400 on 07/08/2005, Bruce Black wrote about Re: Vintage IBM
Mainframe Stuff:
For those of us who long for the punchcard days, here is the virtual
punchcard site
http://www.facade.com/legacy/punchcard/
That brings back memories although it seems to be a BCD (Pre-360) not
a EBCDIC (360 class) Card Punch since it does not understand Lower
Case or other EBCDIC only Characters.
I remember once when I had to write a program to convert from
Card-Image EBCDIC (ie: The list of what holes are punched) into
Internal EBCDIC (which bits are on) due to a need to read a card in
Column Binary Mode and convert it to what would have been read if the
normal read command had been used. The cards were punched with both
Column Binary and standard EBCDIC columns and were being read though
a 2501 (one pass of the card) reader not a 2540 (where the card was
buffered and you could read the data from the buffer without ejecting
the card so you could read it first in Column Binary Mode and then in
Standard Mode [ejecting the card] with the invalid combination
support masked [so it would not choke on the CB columns]).
The major effort turned out to be creating the conversion tables.
Once that was done it was a number of TRs to create an internal
mapping of the holes followed by an OC to merge the top and bottom 6
rows of each column into single bytes followed by the actual TR to do
the conversion. Error checking was the same code (using different
tables) ending in a TRT in lieu of the final TR (to check for more
than one punch in the 1-7 rows [any combination of 12/11/0/8/9
punches were valid but only one punch was allowed in the 1-7 rows for
valid EBCDIC]).
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