No problem! If you would have some follow-up questions then don't hesitate to ask. In case of most problems here you should be covered with your basic

char    input[BUFSIZ];
int     c;
int     count_characters = 0;

while((c = getchar()) != EOF)
{
    if(count_characters == BUFSIZ)
    {
        break;
    }
    else
    {
        input[count_characters] = c;
    }
    count_characters += 1;
}

or similar (like ones using scanf etc). I'm not really a fan of this book, but there's quite a lot of essential input handling in The C Programming Language by Brian Kernighan and Dennis Ritchie. Sorry if that's too basic, I'm not that good with gauging what others may know.

I hope that it helped. Again, if you would need some more directions or aid then feel free to ask.