_control87, _controlfp

Go Up to float.h Index

Header File

float.h

Prototype

unsigned int _control87(unsigned int newcw, unsigned int mask);
unsigned int _controlfp(unsigned int newcw, unsigned int mask);

Description

Manipulates the floating-point control word.

_control87 retrieves or changes the floating-point control word.

The floating-point control word is an unsigned int that, bit by bit, specifies certain modes in the floating-point package; namely, the precision, infinity, and rounding modes. Changing these modes lets you mask or unmask floating-point exceptions.

_control87 matches the bits in mask to the bits in newcw. If a mask bit equals 1, the corresponding bit in newcw contains the new value for the same bit in the floating-point control word, and _control87 sets that bit in the control word to the new value.

Here is a simple illustration:

If mask equals 0, _control87 returns the floating-point control word without altering it.

_controlfp is for Microsoft compatibility. _controlfp is identical to _control87 except that it always removes (turns off) the EM_DEMORMAL bit from the mask parameter.

Return Value

The bits in the value returned reflect the new floating-point control word. For a complete definition of the bits returned by _control87, see the header file float.h.

Portability

See Also

• FPU
• System.Math.SetExceptionMask

• C++ Reference
• Floating-Point
• C++

• AMMigrate