.fseek

.fseek handle, address

Sets the file pointer position in file handle to position address (in bytes).

; Open the file 'hello.txt' and include the data, reversing it.

.fopen fhnd, "hello.txt"        ; fhnd is our handle
.fsize fhnd, hello_size         ; hello_size = size of "hello.txt" in bytes

.for i, hello_size - 1, 0, -1   ; Go through each byte, backwards.
    .fseek fhnd, i
    .fpeek fhnd, chr
    .db chr
.loop

.fclose fhnd                    ; Close our file handle.