Question

I have the string temp[256] and inside it there’s a double number, such as 0.125 and such, and everything is going well though some times it gets a number that’s too big for a double number, like 0.888888888888888888888888888888888888888883, and the double number only holds like 7 numbers instead of all.

I’ve been using the atof to convert the string into the double, but I think the problem is the double here, because it doesn’t have enough space for all the numbers….
This is what I wrote :

char temp[256]; // Has the number inside it
double temp_num = 0; // need to put the string inside this variable
temp_num = atof(temp);
printf ("%f\n", temp_num);

the output from the print is fine as long as the number isn’t larger then 7 digits after the zero, but if it’s a number like 0.8815818188888888888888888888888888888888888888888143, it only prints me the 7 first digits, like in this example it’ll print 8815818 instead of the whole number…
so I guess I need a bigger variable ?

Answer 1

Printf have a default behavior of printing only 7 digits after the zero when dealing with doubles or floats however you can change that behavior and control how many numbers after the zero printf prints like this

printf ("%.20f\n", temp_num);

Here you get 20 digits after the zero.

For more details please refer to:

1. http://www.cplusplus.com/reference/clibrary/cstdio/printf/
2. The c programming language second edition.