cppreference.com > Standard C String and Character > atoi atoi Syntax:
      #include <stdlib.h>
      int atoi( const char *str );
The atoi() function converts str into an integer, and returns that integer. str should start with some sort of number, and atoi() will stop reading from str as soon as a non-numerical character has been read. For example,
       i = atoi( "512.035" );
would result in i being set to 512. You can use (Standard C I/O) sprintf() to convert a number into a string. Related topics: atof atol (Standard C I/O) sprintf