How can I convert a String to a Number

The standard C library provides several functions for converting strings to numbers of all formats (integers, longs, floats, and so on) and vice versa.

 The following functions can be used to convert strings to numbers :

Function                     Name Purpose

atof()                Converts a string to a double-precision floating-point value.

atoi()                Converts a string to an integer.

atol()                Converts a string to a long integer.

strtod()             Converts a string to a double-precision floating-point value and

reports any leftover numbers that could not be converted.

strtol()              Converts a string to a long integer and reports any leftover numbers

that could not be converted.

strtoul()            Converts a string to an unsigned long integer and reports any

leftover numbers that could not be converted.