I have been trying to get my code to do the following:
Fill the first 10 indexes in string 1 & 2 with random characters
Fill the first 20 indexes with random characters in string 3

print all 3 strings out

concatenate the 2nd onto the first string (then print it out)
and a couple of other things which I have already figured out, but generating random characters has been really giving me a hard time...

I'm not exactly sure how to fill a string with random characters.

I can generate random strings, but I don't think that is really the same?

Here is what my code looks like now:

Code:
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>


int main()
{
        char str[100] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
        char str2[100] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
        char str3[100] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};


        float x = strcmp(str, str3);
        float abs = fabs(x);
        int random = rand() %26;
        char randomLetter = 'a' + random;
        int i;


        srand(time(NULL));


        for(i = 0, i < 10 ; i++;);
        {
        int random = rand();
        }


        printf("Str1: %s\n", str);
        printf("Str2: %s\n", str2);
        printf("Str3: %s\n", str3);


        strcat(str, str2);
        printf("New Str1: %s\n", str);


        printf("Distance: %f\n", x);
        printf("Abs Distance: %f\n", abs);
        printf("Sqrt Distance: %f\n", sqrt(abs));




        return 0;
}