How to convert string to float?

Question

#include
#include

int main() 
{
    char s[100] =\"4.0800\" ; 

    printf(\"float value : %4.8f\\n\" ,(float) atoll(s)); 
    return         


        

Answer 1

Use atof() or strtof()* instead:

printf("float value : %4.8f\n" ,atof(s)); 
printf("float value : %4.8f\n" ,strtof(s, NULL)); 

http://www.cplusplus.com/reference/clibrary/cstdlib/atof/
http://www.cplusplus.com/reference/cstdlib/strtof/

• atoll() is meant for integers.
• atof()/strtof() is for floats.

The reason why you only get 4.00 with atoll() is because it stops parsing when it finds the first non-digit.

*Note that strtof() requires C99 or C++11.