I would think you could use read to read in 128-bit records, and use unpack to 'process' them, and you'll probably find that it's fast enough. As for whether to read it record-by-record, or all-at-once, that probably depends on your needs, and your system's capabilities. 100MB is really not so huge, but then again, for all I know you're running on a Commodore-64, so you might have problems slurping 100MB into core...