The atoi, atof and atol utility functions are used to perform string to numeric conversion. As indicated by the last letter in function names, these functions convert the argument string to an integer, floating and long number. Note that the argument string should contain a number of appropriate type as text, optionally preceded by whitespace. For example, the atof function can successfully convert strings such as" 1.23", "3.21El0", etc. The conversion stops when an inappropriate character is encountered in the input string. Thus, these functions will also be able to convert strings such as "-1. 23ABC", "3. 21E10ABc". If conversion is successful, these functions return the converted value, otherwise zero.