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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 and then clears the floating-point status word.  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

       Returns:     Floating-point status word before clearing

         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());
           }