Write function to implement string operations such as compare, concatenate, string length. Convince the parameters passing techniques.

#include <stdio.h>
#include <string.h>
int main()
{
    int length(char str[100]);
    int compare(char s1[100], char s2[100]);
    void concat(char s1[100], char s2[100]);
    
    
        int option, result;
        char str[100], s1[100], s2[100];
        do
        {
            printf(“1.String length \n”);
            printf(“2.string comparision \n”);
            printf(“3.string concatenation \n”);
            printf(“4.quit \n”);
            printf(“enter your choice \n”);
            scanf(“%d”, &option);
            switch (option)
            {
            case 1:
                printf(“enter string \n”);
                scanf(“%s”, &str);
                result = length(str);
                printf(“the length of string= %d\n”, result);
                break;
            case 2:
                printf(“enter 1st string\n”);
                scanf(“%s”, &s1);
                printf(“enter 2nd string\n”);
                scanf(“%s”, &s2);
                result = compare(s1, s2);
                if (result == 0)
                {
                    printf(“strings are equal \n”);
                }
                else
                {
                    printf(“strings are not equal \n”);
                    break;
                }

            case 3:
                printf(“enter two strings\n”);
                scanf(“%s%s”, s1, s2);
                concat(s1, s2);
                printf(“result=%s \n”, s1);
                break;
            }
        } while (option <= 3);
        return 0;
}
    int length(char str[100])
    {
        int i = 0;
        while (str[i] != ‘\0’)
            i++;
        return (i);
    }
    int compare(char s1[100], char s2[100])
    {
        int i = 0;
        while (s1[i] != ‘\0’)
        {
            if (s1[i] > s2[i])
                return (1);
            else if (s1[i] < s2[i])
                return (-1);
            i++;
        }
        return 0;
    }
    void concat(char s1[100], char s2[100])
    {
        int i, j;
        i = 0;
        while (s1[i] != ‘\0’)
            i++;
        for (j = 0; s2[j] != ‘\0’; i++, j++)
            s1[i] = s2[j];
        s1[i] = ‘\0’;
    }