On ia32 systems, the FPU control word includes bits that control the FPU's precision, rounding mode, and whether exceptions generate signals if they occur. You can read the control word value with GETCONTROLFPQQ (ia32 only) to find out the current control settings, and you can change the control word with SETCONTROLFPQQ (ia32 only).
Each bit in the floating-point control word corresponds to a mode of
the floating-point math processor. The DFLIB.F90 module file in the ...\DF98\INCLUDE
folder contains the INTEGER(2) parameters defined for the control word, as shown
in the following table:
| Parameter Name | Value in Hex | Description |
|---|---|---|
| FPCW$MCW_IC | #1000 | Infinity control mask |
| FPCW$AFFINE | #1000 | Affine infinity |
| FPCW$PROJECTIVE | #0000 | Projective infinity |
| FPCW$MCW_PC | #0300 | Precision control mask |
| FPCW$64 | #0300 | 64-bit precision |
| FPCW$53 | #0200 | 53-bit precision |
| FPCW$24 | #0000 | 24-bit precision |
| FPCW$MCW_RC | #0C00 | Rounding control mask |
| FPCW$CHOP | #0C00 | Truncate |
| FPCW$UP | #0800 | Round up |
| FPCW$DOWN | #0400 | Round down |
| FPCW$NEAR | #0000 | Round to nearest |
| FPCW$MCW_EM | #003F | Exception mask |
| FPCW$INVALID | #0001 | Allow invalid numbers |
| FPCW$DENORMAL | #0002 | Allow denormals (very small numbers) |
| FPCW$ZERODIVIDE | #0004 | Allow divide by zero |
| FPCW$OVERFLOW | #0008 | Allow overflow |
| FPCW$UNDERFLOW | #0010 | Allow underflow |
| FPCW$INEXACT | #0020 | Allow inexact precision |
The control word defaults are:
For more information: