Keith, Are you sure that a binary format is necessary? I find the current format very convenient for debugging and highly extensible, and I would be very grateful if you could make sure that the parser is as efficient as possible before going binrary. But if you do... KP> A brute-force approach would be to define structures to pad KP> appropriately (as the X headers do) and then permit entries for KP> both byte orders. Please do not make the format overly flexible -- it's much easier to make a single code path efficient and correct. Both byte-swapping and byte-aligned access to data are reasonably fast for the amounts of data that we're dealing with, so unless profiling shows otherwise, the reasonable thing to do is to put everything in Motorola-endian byte-aligned form. Juliusz