_clear87

Description

Gets and clears the floating-point status word.

#include <float.h>

unsigned int _clear87( void );

Remarks

The _clear87 function gets and clears the floating-point status word. The floating-point status word is a combination of the 8087/80287 status word and other conditions detected by the 8087/80287 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.

Many of the math library functions modify the 8087/80287 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.

Compatibility

Standards:None

16-Bit:DOS, QWIN, WIN, WIN DLL

32-Bit:DOS32X

See Also

_control87, _status87

Example

/* CLEAR87.C: This program creates various floating-point problems,

* then uses _clear87 to report on these problems.

* Compile this program with Optimizations disabled (/Od). Otherwise

* the optimizer will remove the code associated with the unused

* floating-point values.

*/

#include <stdio.h>

#include <float.h>

void main( void )

{

double a = 1e-40, b;

float x, y;

printf( "Status: %.4x - clear\n", _clear87() );

/* Store 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() );

}

Output

Status: 0000 - clear

Status: 0030 - inexact, underflow

Status: 0002 - denormal