FORTRAN 77 on PDP-11

I have been having some fun with Prime Numbers using FORTRAN 77 under RT-11 on a PDP-11. Since I rapidly run out of the capacity of 32 bit numbers (INTEGER * 4 NUMBER), I have started to use 64 bit values (REAL * 8 NUMBER) but the conversion routines leave a lot to be desired on output. When using F32.0, I can count on only about 15 digits of accuracy even though the values are often accurate to an exact integer. If needed, I can write my own conversion routines, but I though I might inquire if anyone knows of any libraries which are exact or better still, multi-precision libraries which can handle up to 128 bit integers? Can anyone Sincerely yours, Jerome Fine -- If you attempted to send a reply and the original e-mail address has been discontinued due a high volume of junk e-mail, then the semi-permanent e-mail address can be obtained by replacing the four characters preceding the 'at' with the four digits of the current year.