I see the problem with your matrix program. You're using counter to decide when to end, but you're also using it as an array index and preventing it from walking off the edge. So it'll never get higher than 8, and never end.

You're also preventing it from overwriting itself, i.e. changing any characters other than '.', so it'd be possible for itself to wall itself in like the worm game and freeze.

---------- Post updated at 10:32 AM ---------- Previous update was at 10:21 AM ----------

In your second program, you're reading numbers when you should be reading a string. You don't even check how many numbers you read, so you just go right into data you never read and print all kinds of garbage.

I'd do it like this:

Code:

char buf[128];
int n;

fprintf(stderr, "Input string: "); // no newline, so need stderr or fflush(stdout)
fgets(buf, 128, stdin); // read one exact line.

for(n=0; buf[n] != '\0'; n++)
{
        int c;

        if((buf[n] >= 'A') && (buf[n] <= 'Z')) c=buf[n]-'A'; //A=0, B=1,...
        else if((buf[n] >= 'a') && (buf[n] <= 'z')) c=buf[n]-'a';//a=0,b=1,...
        else // print everything else raw, and skip conversion
        {
                printf("%c", buf[n]);
                continue;
        }

        printf("%d", (c/3) + 1);
}