The cd command ("Change directory"), sometimes also spelled chdir, is built into any version of the Unix shell that you are likely to find. It is also found in DOS and the Windows CLI (cmd.exe or command.com), where it means the same thing as it does in a shell on FreeBSD and other unixlike OSes.
A notable differences between the Unix shell cd and the DOS version is that, all shell versions of cd require a space between cd and the name of the directory to change to, even if the name is the symbols . (current directory), .. (container directory), or / (file-system root directory).
C:\Windows> cd\stuff (windows) splat# cd /stuff (unixlike)
C:\Windows> cd.. (windows) splat# cd .. (unixlike)
cd by itself will send you to your home directory, as will cd ~. cd - will show you and then change your directory to the last directory you were in, as below:
[dave]@deus /var/log % cd ~ [dave]@deus ~ % pwd /home/dave [dave]@deus ~ % cd /etc [dave]@deus /etc % cd - /home/dave [dave]@deus ~ %
.. up one level, e.g., cd .. in /e/foo will take you to /e/ - previous directory ~ home ~username home directory of the user "username" . the directory I am in. Not used very often with cd but more often with commands.