Converting the String to an Integer in C

In this tutorial, we are going to learn about how to convert the string to a integer in C language.

Using atoi() function

In C, we can use the atoi() function to convert a numeric string to a integer.

The atoi() function is available in stdlib.h library.

Here is an example, that converts the string "1011" to an integer 1011:

#include<stdio.h>
#include <stdlib.h>

int main() {
    // Converting a numeric string to integer
    char str[5] = "1011";
    int a = atoi(str);
    printf("Converting '1011': %d\n", a);
}

If a string starts with alpanumeric then atoi() function returns 0.

Example:

#include<stdio.h>
#include <stdlib.h>

int main() {
    // Converting a numeric string to integer
    char str[5] = "olaa";
    int a = atoi(str);
    printf("Converting '1011': %d\n", a);
}

Output:

0