DOS / Functions / 42

            INT 21 - DOS 2+ - MOVE FILE READ/WRITE POINTER (LSEEK)

Input	DOS1	N	DOS2	Y	DOS3	Y	DOS5	Y	Output
AX	42h		Seek Method		New Offset (Low) / Error Code				AX
BX	File Handle								BX
CX	Offset (High)								CX
DX	Offset (Low)				New Offset (High)				DX
ES:DI					Set if Error				CF

Seek Method:    0 = From begin of File
                1 = From Present Position
                2 = From End of File

See Also 40h 59h Error Codes