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What are 'overpunched signed fields'?

I know it's something to do with ASCII and EBCDIC, but I can't find anything online which gives me a concise explanation.
Could someone give me a clue?
Not old enough Send private email
Wednesday, March 29, 2006
Look up in a COBOL reference manual for the SIGN clause.  When describing the layout you specify whether the sign is separate from the numeric represention or whether it is part of the numeric represenation.

-1234  <-- separate sign leading
123F    <-- trailing sign overpunch
Wednesday, March 29, 2006
Here is some genuine Turbo Pascal code that'll give you a hint.  Now I've done my good deed for today...

function ConvertPackedNumber(PassedString : String) : String;
 WorkString : string;
 i          : word;
 if length(PassedString) <= 1 then
    ConvertPackedNumber := PassedString;

 if PassedString[length(PassedString)] = '-' then
  PassedString := '-' + Copy(PassedString,1,length(PassedString)-1);

 for i := 1 to length(PassedString)-1 do
  if not (PassedString[i] in ['0'..'9']) then
    ConvertPackedNumber := PassedString;

 WorkString := Copy(PassedString,1,length(PassedString)-1) +
 if PassedString[length(PassedString)] in ['}','J','K','L','M','N','O','P','Q','R'] then
  WorkString := '-' + WorkString;

 ConvertPackedNumber := WorkString;
Wednesday, March 29, 2006
Cheers guys. I've got it now.
Not old enough Send private email
Wednesday, March 29, 2006
Those are artifacts of the actual practice.  See et al. which should make it clear that the X and Y rows (11 and 12 rows) of the Hollerith card are where "overpunches" really exist(ed).

By using "overpunched" signs one was able to save a card column per field on numeric data.  Hard to believe so few people seem to be left who remember using these things on a daily basis.
Artad Gobeski
Wednesday, March 29, 2006
So few people in this forum - in the trenches of mainframe America where all the airline reservations and bank statement processing happen, we use them all the time, and wonder what the Internets are all about and why you'd want one.
NetFreak Send private email
Thursday, March 30, 2006
Crop circles?
Vaughan Bromfield Send private email
Monday, April 10, 2006

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