If you execute ____, the contents of file1 are sorted and the results are stored in file2.

Unix and linux are ____ systems, which allow one user to execute more than one program at a time.

Default permissions are determined by the _____.

When you type the name of a command, the shell finds it in:

The notation '.' in an ls listing, is shorthand for:

Files in Unix may be a representation of the system's: