cd is a command line command used to change the current
working directory in the Unix and DOS operating systems. It is also available
for use in Unix shell scripts or DOS batch files. cd is frequently included
built into certain shells such as the Bourne shell, tcsh, bash (where it calls
the chdir() POSIX C function) .
A directory is a logical section of a filesystem used to
hold files. Directories may also contain other directories. The cd command can
be used to change into a subdirectory, move back into the parent directory,
move all the way back to the root (/ in UNIX, \ in DOS) or move to any given
directory.
$ cd ../private/files