GETCONTROLFPQQ

Module

USE IFPORT

Syntax

CALL GETCONTROLFPQQ (controlword)

controlword

(Output) INTEGER(2). Floating-point processor control word. The floating-point control word is a bit flag that controls various modes of the floating-point coprocessor. The control word can be any of the following constants (defined in IFPORT.F90): Parameter name Hex value Description FPCW$MCW_IC Z'1000' Infinity control mask FPCW$AFFINE Z'1000' Affine infinity FPCW$PROJECTIVE Z'0000' Projective infinity FPCW$MCW_PC Z'0300' Precision control mask FPCW$64 Z'0300' 64-bit precision FPCW$53 Z'0200' 53-bit precision FPCW$24 Z'0000' 24-bit precision FPCW$MCW_RC Z'0C00' Rounding control mask FPCW$CHOP Z'0C00' Truncate FPCW$UP Z'0800' Round up FPCW$DOWN Z'0400' Round down FPCW$NEAR Z'0000' Round to nearest FPCW$MCW_EM Z'003F' Exception mask FPCW$INVALID Z'0001' Allow invalid numbers FPCW$DENORMAL Z'0002' Allow denormals (very small numbers) FPCW$ZERODIVIDE Z'0004' Allow divide by zero FPCW$OVERFLOW Z'0008' Allow overflow FPCW$UNDERFLOW Z'0010' Allow underflow FPCW$INEXACT Z'0020' Allow inexact precision

An exception is disabled if its control bit is set to 1. An exception is enabled if its control bit is cleared to 0. Exceptions can be disabled by setting the control bits to 1 with SETCONTROLFPQQ.

If an exception is disabled, it does not cause an interrupt when it occurs. Instead, floating-point processes generate an appropriate special value (NaN or signed infinity), but the program continues.

You can find out which exceptions (if any) occurred by calling GETSTATUSFPQQ. If errors on floating-point exceptions are enabled (by clearing the control bits to 0 with SETCONTROLFPQQ), the operating system generates an interrupt when the exception occurs. By default, these interrupts cause run-time errors, but you can capture the interrupts with SIGNALQQ and branch to your own error-handling routines.

You can use GETCONTROLFPQQ to retrieve the current control word and SETCONTROLFPQQ to change the control word. Most users do not need to change the default settings. For a full discussion of the floating-point control word, exceptions, and error handling, see Building Applications: The Floating-Point Environment Overview.

Compatibility

CONSOLE STANDARD GRAPHICS QUICKWIN GRAPHICS WINDOWS DLL LIB

Example

USE IFPORT

INTEGER(2) control

CALL GETCONTROLFPQQ (control)

!if not rounding down

IF (IAND(control, FPCW$DOWN) .NE. FPCW$DOWN) THEN

control = IAND(control, NOT(FPCW$MCW_RC)) ! clear all

! rounding

control = IOR(control, FPCW$DOWN) ! set to

! round down

CALL SETCONTROLFPQQ(control)

END IF

END