Purpose

The CHECK-INPUT statement in field General Check logic allows user input to be tested before the processing of system-defined characters.
 

Operation

In normal field input, certain system-defined characters such as cancel, end-of-data, forward-tab, and backward-tab are processed before General Check logic is executed.  

The CHECK-INPUT statement postpones the processing of these special characters until after General Check logic has been executed.

CHECK-INPUT also allows you to test for the entry of certain Function Keys.  Because different Function Keys are processed at different times during the input operations, the following Function Keys are the only ones which can be tested for using CHECK-INPUT:

INSET, ADD, CHANGE, DELETE and LOOKUP
CANCEL and EOD
FORWARD TAB and BACK TAB
NEXT and PREVIOUS
UP ARROW, LEFT ARROW and RIGHT ARROW
 

Remarks

CHECK-INPUT must be the first statement in the logic and is only valid in General Check logic (see Screen Function Dynamic Process Points).  

FLD statements are ignored, but if an MSG command is issued control returns to the current field.
 

Example

CHECK-INPUT
IF $INPUT="."THEN
MSG 3
ENDIF

This logic does not allow ‘.’ to be entered for this field.  If detected, message 3 appears, and the field must be re-input.

CHECK-INPUT
IF @FNKEY=10 THEN
MSG 3
ENDIF

This logic checks for EOD.  If this occurs, message 3 appears.