FORTRAN 77 on PDP-11

Jerome> If the code could be written in FORTRAN, it would be fairly Jerome> simple. Then common source code could be used. But, even if Jerome> possible, FORTRAN is simply not structured to easily allow Jerome> multiple operations on succeeding values which are required Jerome> when adding carry bits between even two words, let alone 8 * Jerome> 16 bit words needed for 128 bit arithmetic. Which means Jerome> coding in assembler! Actually, carry is easy. There's a simple trick I learned on the Alpha, but it applies anywhere. Given UNSIGNED variables: c = a + b; if (c < a) { /* you got a carry */ } Tweak as needed for signed. Jerome> Since I do NOT find that to be a problem, I am not very Jerome> concerned. But in case there was already a library around, I Jerome> thought I would ask. Jerome> By the way, are there any standard algorithms for the 4 basic Jerome> operations (add, subtract, multiply and divide) for 128 bit Jerome> numbers which are composed of 8 * 16 bit words? As per your Jerome> suggestion, I would probably use: CHARACTER * 16 ARRAY ( nnn Jerome> ) Knuth vol. 1 may help. Reading GNU MP may also help, though that is likely to be optimized for much bigger integers (1024 bits or more). paul