https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107370
--- Comment #16 from jacob navia <jacob at jacob dot remcomp.fr> --- Sorry but the program I used was compiled with gcc. It suffers from lack of precision too. In ANY case, in decimal now, the square root of 2 is 1.414 213 562 373 095 048 801 688 724 209 698 078 GP PARI calculator 1.414 213 562 373 095 145 547 462 185 874 gcc: only the first 15 digits are OK ^^^^^ In ANOTHER example: #include <stdio.h> #include <math.h> int main(void) { printf("%.30Lg \n",sqrtl(powl(2,225))); } This produces: 7.34301663720716943338259962711e+33 But bc produces ~/lcc/book/test % bc bc 1.06 Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc. This is free software with ABSOLUTELY NO WARRANTY. For details type `warranty'. scale=32 sqrt(2^225) 7343016637207168931428032607349397.48923080385562326502615381523522 To make things clearer I put now the results side by side 7.34301663720716943338259962711e+33 gcc 734301663720716 8931428032607349397.48923080385562326502615381523522 bc As you can see, after the 15th digits all others are wrong!!! Jacob