C language convert char to int

Convert char type to int in C language.
The char type is saved as an ASCII value.
Convert numeric characters:

/*
Example: char to int in C language
*/

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <stdbool.h>

int main(int argc, char *argv[]) {
    char chr = '9';
    int x = (int)(chr - '0');

    printf("char value: %d.\n", x);
    return 0;
}

Convert characters:

/*
Example: char to int in C language
*/

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <stdbool.h>

int main(int argc, char *argv[]) {
    char chr = 'a';
    int x = (int)(chr);

    printf("char value: %d.\n", x);
    return 0;
}

Convert string

/*
Example: char string to int  in C language
*/

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <stdbool.h>

int main(int argc, char *argv[]) {
    char str[10];
    strcpy(str, "77123456");
    int val = atoi(str);

    printf("%d.\n", val);
    return 0;
}