Alias allows you to create an alternate name for other DOS commands.
If Alias is used with no parameters, it will display the current
list of Aliases defined within the current shell.
Using a pair of square brackets within an alias allows you to
provide the 'new' dos command with parameters.
If no parameters are specified, the current list of aliases are
displayed.
Alias DF "Type [] number"
By typing "DF S:Shell-Startup" in the shell, you are actually
executing the command "Type S:Shell-Startup number". This will
display the contents of the S:Shell-Startup file in the shell
with line numbers on the left hand side.