Odd "endianness" [was Re: RE: Base 64 posts to the list]

On Mon, Dec 5, 2016 at 11:14 AM, Dave Wade <dave.g4ugm at gmail.com> wrote: 4 padding bits scattered through the word). PDP-10: 36 bit word, 5*7bit characters. PDP-15: 18 bit word, but it was so long ago, I don't remember.... CDC 6000: 60 bit word, 10 six bit characters. PDP11 "middle endian" see "NUXI problem: http://www.catb.org/jargon/html/M/middle-endian.html PDP11 RADIX-50 3 characters packed into a 16 bit word; each character in a 0:39 set. Back to Der Mouse question re: non-symmetrical mapping.... hton and ntoh are not meant has generalized data conversion; they are intended as network data packet field conversion; the domain of ntohl is a 32bit unsigned integer; the range is a host object larger enough to contain all possible values. For hosts that are base 2 and have word sizes that divide 32bits evenly, the functions would typically be identity or bit rearrangement, and the htonl and ntohl functions would be symmetric -- I suspect that a good mathematician could 'prove' that cycle length is always 2 given the constraints. Cases like 36 bits words mean that htonl is "lossy"; it throws away bits and and ntohl pads the result with 0s -- they are not symmetrical, thus the answer to the order-2 cycle question is 'not applicable' -- Charles