8 bits per byte is standard now (if you use a PDP-8 or something, things may get more interesting...). On your second question, Configure (the Perl configuration detector script - it gets run before your perl is compiled) has a test for _byte_ order. It doesn't matter to the perl programmer, since standard perl numbers are in whatever byteorder is native to the platform. If you really care, pack is your friend (in particular the formats N, n, V, and v).