the command interpreter.
It is not built-in, but is just a program
and you can change your shell.
-Everybody has her own favorite one.
+Everybody has their own favorite one.
The standard one is called
.IR sh .
See also
.PP
A session might go like:
.PP
-.RS
-.nf
+.in +4n
+.EX
.RB "knuth login: " aeb
.RB "Password: " ********
.RB "$ " date
.RB "$ " "grep maja tel2"
maja 0501\-1136285
$
-.fi
-.RE
+.EE
+.in
.PP
Here typing Control-D ended the session.
.PP