Program Logic Manual - All about the IBM 1130 Computing System

Significant variables:Symbolic locationCZ904CZ904+1CZ902CZ923Contents/UseStart read or punch IOCC, set by program depending on function used toinitiate operation.If read, CZ904 + 1 = CZ906 + 1If write, CZ904 + 1 = CZ908 + 1Read or Punch IOCC, set by program depending on function to read or punchcolumns.If read, CZ902 + 1 = CZ906If write, CZ902 + 1 = CZ908Address pointer to I/0 area, incremented on each column interrupt.CZ925 Original I/O area address -1.CZ920CZ010$RWCZDSW is saved here on an operation-complete interrupt.Switch used for waiting for interrupt:Set positive when waiting for any interrupt.Set zero when column interrupt occurs.Set negative when op-complete interrupt occurs.Previous operation switch:/0000 = previous operation was a read./0002 = previous operation was a write.If a write function is to be performed and the previous operation was a write,this switch causes CARDZ to read a card and test for // in columns 1-2.CZ918CZ918-3thruCZ918Switch used to test for /1 card before writing on it; zero means only readingor previous operation before write was a read.Buffer area for saving first 3 columns; rest of card is read into fourth wordwhen reading before write.Program Analysis Procedures 141