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_control87
==========

Syntax
------

     #include <float.h>
     
     unsigned int _control87(unsigned int newcw, unsigned int mask);

Description
-----------

Sets or resets bits in the FPU's control register.  The bits are
defined by macros in float.h, and by this table:

     ---- ---- --XX XXXX = MCW_EM - exception masks (1=handle exception internally, 0=fault)
     ---- ---- ---- ---X = EM_INVALID - invalid operation
     ---- ---- ---- --X- = EM_DENORMAL - denormal operand
     ---- ---- ---- -X-- = EM_ZERODIVIDE - divide by zero
     ---- ---- ---- X--- = EM_OVERFLOW - overflow
     ---- ---- ---X ---- = EM_UNDERFLOW - underflow
     ---- ---- --X- ---- = EM_INEXACT - rounding was required
     ---- --XX ---- ---- = MCW_PC - precision control
     ---- --00 ---- ---- = PC_24 - single precision
     ---- --10 ---- ---- = PC_53 - double precision
     ---- --11 ---- ---- = PC_64 - extended precision
     ---- XX-- ---- ---- = MCW_RC - rounding control
     ---- 00-- ---- ---- = RC_NEAR - round to nearest
     ---- 01-- ---- ---- = RC_DOWN - round towards -Inf
     ---- 10-- ---- ---- = RC_UP - round towards +Inf
     ---- 11-- ---- ---- = RC_CHOP - round towards zero
     ---X ---- ---- ---- = MCW_IC - infinity control (obsolete, always affine)
     ---0 ---- ---- ---- = IC_AFFINE - -Inf < +Inf
     ---1 ---- ---- ---- = IC_PROJECTIVE - -Inf == +Inf

Return Value
------------

The previous control word.