Article: Q40587
Product(s): See article
Version(s): 5.10
Operating System(s): MS-DOS
Keyword(s): ENDUSER | | mspl13_c
Last Modified: 25-MAY-1989
Even if you only want simple arithmetic operations, the 80x87 chip
doesn't provide a means for saving and restoring all of its registers.
Microsoft wrote its library routines for DOS, which for the most part
handle single-process routines, and therefore do not provide the
routines necessary for achieving this effect with the coprocessor
chip.
If you want to develop a program that requires the coprocessor to be
reentrant, you must provide your own routines that save and restore
the registers of the coprocessor.