I'm replying to several postings at once here, since I'm in digest mode anyway... We all know the subject by now, doing bignum arithmetic in F77 on a PDP-11, and all the side topics this have generated... This have now been covered, so I think I can safely skip this. If you really need some help in figuring out what little and bigendian is, then say so, and we'll take a crash course. And I don't see the need. When you pass arrays as arguments in FORTRAN, you only pass pointers, and actually access the parameters in the callers address space. So no allocation is done, nor need to be done. Using REAL*8 as a return value from the function is actually what you are most interested in anyway when you go down this lane, since it's the result you might want to allocate space for automatically. However, it will not help you beond 64 bits anyway, so it's a dead end. Bite the bullet and do it in a way that will deal with arbitrary large values, if that's what you want. This code has a bug in it, as has been pointed out. You actually needs to do the ADC for all subsequent words after each add step, since every ADC in turn also can generate a carry. Yes, and that is little-endian. Well, actually, your code only assumes that the *words* are little endian. You don't look at individual bytes, and thus the CPU can have them either little or bigendian without you knowing. Please stop looking at floating point data, since it's a whole other game. I'll even repeat this: DON'T TRY TO USE FP, IT'S A WHOLE OTHER ISSUE IN ALL ASPECTS! Even endianess don't actually apply to fp. If you look at how 16-bit integers are stored in memory, you'll see that the most significant bit of the 16 is stored in bit 7 of byte 1. And thus, the least significan bit is stored in bit 0 of byte 0, which is a small-endian machine. [...] What FORTRAN 77 are you using??? You gotta be kidding. Here is my small example code: ----------- PDP-11 FORTRAN-77 V5.4-26 20:35:33 31-JUL-05 Page 1 TMUL.FTN;1 0001 PROGRAM TEST 0002 INTEGER*4 X,Y,Z 0003 X = 42 0004 Y = 4711 0005 Z = X*Y 0006 END PDP-11 FORTRAN-77 V5.4-26 20:35:33 31-JUL-05 Page 2 TMUL.FTN;1 .TITLE TEST .IDENT 31JUL 000000 .PSECT $CODE1 000000 JSR PC,OTI$ 000004 MOV #76400,-(SP) 000010 MOV #76733,R4 000014 JSR R4,@$NAM$ ; 0003 000020 MOV #-3,$SEQC 000026 MOV #52,X 000034 CLR X+2 ; 0004 000040 MOV #11147,Y 000046 CLR Y+2 ; 0005 000052 MOV X+2,-(SP) 000056 MOV X,-(SP) 000062 MOV Y+2,-(SP) 000066 MOV Y,-(SP) 000072 JSR R4,MLJS$ 000076 MOV (SP)+,Z 000102 MOV (SP)+,Z+2 ; 0006 000106 JSR PC,EXIT$ ------------ Notice how the compiler pushes two 32-bit integers on the stack and calls MLJS$ Where did you find any FP stuff??? The rest of your questions about F77 are irrelevant, since you are asking things on the compiler, but the compiler clearly don't do what you say. The reason for using the stack is that FORTAN-77 have a calling convention using R4 as the argument pointer. And since the function for doing 32-bit multiplications is just a function, the parameters needs to be passed somehow, and the stack is a very good choise. As for the algoritm for the sieve, I'll skip that part, since I haven't given it enough thought to see if what you say make sense or not. And I'm not overly interested in primes, so please don't ask me. I remember from my math classes that a sieve is both memory inefficient and slow. Doing factorization is rather fast in comparision, so unless you want to print all primes you can think of, it would be faster. Doing them all will be slower, but will use a fixed, very small amount of memory anyhow. [---] [...] Good enough that we hopefully can terminate that question? The (I believe) official term is "middle-endian". :-) And like I believe I said before, FORTRAN-77 on the PDP-11 is pure little-endian. FORTRAN IV however, is middle-endian. I think I've written a small test program in most languages that have 32-bits integers on the PDP-11, which shows what byte order they use, if someone is interested. [...] Yup. Yup. Nope. The PDP-11 don't have a RET instruction. RETURN is actually a macro, and is the usual name used for this. If you want the actuall assembler mnemonic, it's "RTS PC" :-) CALL is the same deal... Don't exist either, and is instead a macro, so "CALL nnn" gets translated to "JSR PC,nnn" Johnny Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt at update.uu.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol