Int 21H Function 42H
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▀ This function uses a method code and a double-precision (32-bit) value to
set the file pointer. The next record read or written in the file will
begin at the new file pointer location.
▀ Method 02H may be used to find the size of the file by calling Int 21H
Function 42H with an offset of 0 and examining the pointer location that
is returned.
▀ Using methods 01H or 02H, it is possible to set the file pointer to a
location that is before the start of file. If this is done, no error is
returned by this function, but an error will be encountered upon a subse-
quent attempt to read or write the file.
▀ No matter what method is used in the call to this function, the file
pointer returned in DX:AX is always the resulting absolute byte offset
from the start of file.
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