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_clear87()               Get and Clear 8087/80287 Status Word

 #include   <float.h>

 unsigned int  _clear87(void);           Floating-point status word


    _clear87() gets the floating-point status word and then clears it.
    The floating-point status word is combination of the 8087/80287
    status word and other conditions detected by the 8087/80287 exception
    handlers.  The bits in the status word (defined in <float.h>) are
    assigned as follows::

           SW_INVALID           Invalid operation
           SW_DENORMAL          Denormal value
           SW_ZERODIVIDE        Divide by zero
           SW_OVERFLOW          Overflow
           SW_UNDERFLOW         Underflow
           SW_INEXACT           Loss of precision
           SW_UNEMULATED        Unemulated instruction
           SW_SQRTNEG           Square root of negative number
           SW_STACKOVERFLOW     FP stack overflow
           SW_STACKUNDERFLOW    FP stack underflow

    Returns:    Floating-point status word

      Notes:    Because many of the math library functions modify the
                8087/80287 status word, return values from _clear87() are
                guaranteed to be accurate when only one floating-point
                math function or one floating-point operation is
                performed between checks of the floating-point status
                word.

  -------------------------------- Example ---------------------------------

         #include <stdio.h>
         #include <float.h>

         double a = 1e-40,b;
         float x,y;

         main()
         {
              printf("status = %.4x - clear\n",_clear87());
              y = a;          /*store into y is inexact and underflows */
              printf("status = %.4x - inexact, underflow\n",_clear87());
              b = y;          /* y is denormal */
              printf("status = %.4x -denormal\n",_clear87());
          }