Now, this discussion could get quite involved, but we will try to limit it to a few useful things. Having the shell remember the last ``few'' commands we have entered, and some shortcut way of accessing them is a handy thing. With the exception of the original Bourne shell, all shells have some facility for keeping track of command history. Newer shells will allow you to go back through the history using the up and down arrows, as well as using the shortcut starting with a exclamation mark (or ``bang'') followed by at least as many characters as uniquely specifies the command. And this history extends across login's, which can be quite handy.