#include <stdlib.h>long double strtold(const char * restrict start, char restrict ** restrict end);
strtold( ) was added by C99.
The strtold( ) is similar to strtod( ) except that it returns a long double value. If overflow occurs, then either HUGE_VALL or –HUGE_VALL is returned, and the global variable errno is set to ERANGE, indicating a range error. If start does not point to a number, no conversion takes place and zero is returned.
Related functions are atof( ), strtod( ), and strtof( ).