The following message is a courtesy copy of an article that has been posted to bit.listserv.ibm-main,alt.folklore.computers as well.
[EMAIL PROTECTED] (Tony Harminc) writes: > The 2540 was quite happy to read so-called column binary cards, that > is cards with any 12-bit combination of holes punched. (Well, happy > may be the wrong word, but the problems were mechanical rather than > logical, and it was mostly the punching rather than the reading that > gave trouble.) Later readers also had an optional column binary > feature, and the mark sense and later OMR features used the same > scheme. The S/360 interface (implemented in the 2821 control unit > rather than the reader itself) could deliver the 2x6 bits embedded in > two 8-bit bytes. I imagine a 2540 connected to a pre S/360 machine, > would deliver 6-bit characters across the interface. re: http://www.garlic.com/~lynn/2008k.html#42 IBM 029 keypunch -- 0-8-2 overpunch -- what hex code results? http://www.garlic.com/~lynn/2008k.html#43 IBM 029 keypunch -- 0-8-2 overpunch -- what hex code results? on 360 reading column binary, read 80 columns into 160 bytes (i.e. column with effectively 12bits mapped into two 8bit bytes). pre-360 used BCD that mapped a single column into single 6bit value (EBCDIC subset). This was different from "binary" which mapped a column into two 6bit values. from gcard.html ... /3525 card-reader/punch CCW http://www.garlic.com/~lynn/gcard.html#23 read, feed, select stacker CCW: SSD0 F010 3525 just shows "SS" as stacker 1 or 2; a real 2540 ... had 5 pockets, two that were punch only, two that were reader only ... and a middle pocket that could intermixed cards read & cards punched ... so "SS" could be stacker 1, 2, or 3. "D" is either EBCDIC or "card image" (aka column binary ... two bytes per column). My first student programming job was porting 1401 "MPIO" program to 360/30. MPIO was card-to-tape & tape-to-printer/punch utility where the university used 1401 as unit-record front-end to 709 (physically moving tapes back & forth between 1401 and 709). 360/30 was brought in as part of migration that eventually replaced 709 with 360/67. The 360/30 could operate in 1401 hardware emulation mode ... and run the 1401 "MPIO" directly. However, I guess as part of migration to 360 ... I got the task of reimplementing MPIO utility in 360 assembler. I got to invent my own interrupt handlers, storage manager, task manager, device drivers, error recovery, etc. Part of the implementation was differentiating between BCD and binary cards on reading from 2540 ... and also differentiating between BCD and binary from tape ... for punching (punch 80 bytes as BCD or 160 bytes as binary). I also did a program for student registration that used the middle pocket. Normal student registration was sense marked cards on solid manilla colored cards. These were read one at a time from 2540 with stacker (middle) three selected. There was some amount of validating checking done ... and if there was some sort of error ... a blank card would be punched into the middle pocket (behind the registration card in error). The 2540 punch was loaded with cards that had colored stripe on the top edge. When all the cards were pulled from the middle stacker and placed in card tray ... all the registration cards in error were easily identified by an immediately following card with top colored stripe ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
