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C COMPILER LIBRARY FUNCTION REFERENCE->Detailed Descriptions->atoi() atol() atof()atolf()

Summary

#include <stdlib.h>
    
int atoi(const char* string);Convert string to int
long atol(const char* string);Convert string to long
double atof(const char* string);Convert string to double
long double atolf(const char* string);Convert string to long double

Parameter

string    A pointer to the string to be converted.


Description

These functions convert a character string to an integer value (atoi()), a long integer value (atol()), a double precision floating point value (atof()) or a long double precision floating point value.

With atoi() and atol():

After skipping any white space at the beginning of the string, the first character may be +,   or a decimal digit.  The rest of the string is then read until a character is encountered that is not a decimal digit.  This may be the null character.

With atof() and atolf():

After skipping any white space at the beginning of the string, the following format is expected:

 [sign][digits][.digits][E or e][sign][digits]

Conversion terminates when a character is found that does not fit this format.  This may be the null character.


Return Value

These functions return the number produced by interpreting the input string as a decimal number.  Note that no overflow check is carried out and if overflow occurs, then the return value is undefined.  Zero is returned if no conversion takes place.