In C, you should always declare the array size. If you don't, you could run into some nasty seg faults errors that are not easy to debug. Another note for OP would be to always declare your char array to be a size of one larger than what you need because C always ends it's strings with a null terminator ('/0').
For Example if I declare a string as:
char string[] = {'t','e','s','t'}
when you try to print it, it will look something like this: testjhfdkhafhagfdhjkasd. It will print out garbage until it finds a null terminator. And this could also result in another seg fault error.