Because read-after-write verification slows disk operations, the default setting of the verify flag is OFF.Turns off or turns on the operating-system flag for automatic read-after-write verification of data.
Call with:
AH = 2EH
AL = 00H if turning off verify flag
01H if turning on verify flag
DL = 00H (MS-DOS versions 1 and 2)
Returns:
Nothing
Notes:
Because read-after-write verification slows disk operations, the default setting of the verify flag is OFF.
If a particular disk unit's device driver does not support read-after-write verification, this function has no effect.
The current state of the verify flag can be determined using Int 21H Function 54H.
The state of the verify flag is also controlled by the MS-DOS commands VERIFY OFF and VERIFY ON.
Example:
Save the current state of the system verify flag in the variable vflag, then force all subsequent disk writes to be verified.
vflag db 0 ; previous verify flag
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; get verify flag
mov ah,54h ; function number
int 21h ; transfer to MS-DOS
mov vflag,al ; save current flag state
; set verify flag
mov ah,2eh ; function number
mov al,1 ; AL = 1 for verify on
mov dl,0 ; DL must be zero
int 21h ; transfer to MS-DOS
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