IBM 3270 PC Supervisor Crash
  
PSS ID Number: Q12357
Article last modified on 11-02-1994
 
3.x
 
MS-DOS
 

SUMMARY
=======
 
In Word version 3.00, the use of Interrupt Vector 9 is incompatible
with Control Program version 3.00, the operating system of the 3270
PC.
 
According to IBM, "registers must be unchanged when an application
IRETs back to its caller or jumps to the chainon address." Apparently,
the programs in multiple sessions share interrupt vectors by chaining
to them, but they must actually be hiding some information in the
registers.
 
When Word gets an INT 9, it seemingly modifies the registers, then
calls the next in the chain (the one which was in the INT location
when the program started). Operating the way it does, Word actually
causes the supervisor to crash.
 
This problem was corrected in Word versions 4.00 5.00 and 5.50.
 
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Copyright Microsoft Corporation 1994.