1) To see if an input file doesn't exist, a programmer should check for a(n) __________________________. Be as specific as possible.

2) If you are searching for an element in an array of n items, how many elmenet visits must be made in the worst case situation?

3) If you open a file for writing that doesn't exist, the file is created with _________ length.

4) The compiler does not check whether you handle a(n) ________________.