Question

I want codes for randomly selects the word (meaningful or meaningless) from 26 letters. The word contain 6 letters. I have the codes for C program or objective C, or you will give any idea to me.

Answer 1

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

main()
{
    srand(time(NULL));
    for (int i = 0; i < 6; ++i)
    {
        putchar('a' + (rand() % 26));
    }
    putchar('\n');
    return EXIT_SUCCESS;
}

Salt to taste.

Update0

It would seem the OP does not know how to compile the above. If saved into a file called so.c, compile it with make so CFLAGS=-std=c99 from the same folder.