Museum

     Name
          _clear87 - Gets and clears the floating-point status word.

     Syntax
          #include <float.h>

          unsigned int _clear87(void)

     Description
          The _clear87  function gets and clears the floating-point
          status word. The floating-point status word is a combination
          of the 8087/80287/80387 status word and other conditions
          detected by the 8087/80287/80387 exception handler, such as
          floating-point stack overflow and underflow.

     Return Value
          The bits in the value returned indicate the floating-point
          status. See the float.h include file for a complete
          definition of the bits returned by _clear87.

     Notes
          Many of the math library functions modify the
          8087/80287/80387 status word with unpredictable results.
          Return values from _clear87 and _status87 become more
          reliable as fewer floating-point operations are performed
          between known states of the floating-point status word.

     See Also
          _control87(DOS), _status87(DOS)

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

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

          main ( )
           {
                  printf("status  = %.4x - clear\n",_clear87( ));

                  /* storing into y is inexact and underflows: */
                  y = a;
                  printf("status  = %.4x - inexact, underflow\n",
                            _clear87( ));

                  /* y is denormal: */
                  b = y;
                  printf("status  = %.4x - denormal\n",_clear87( ));
           }

          This program creates various floating-point problems, then
          uses _clear87 to report on these problems.

                                                (printed 6/18/89)