The Lisp interpreter uses > for a prompt. If you type
something and press the enter key (what we old fogeys
call a carriage return), the interpreter evaluates whatever
you typed. Numbers evaluate to themselves:
> 1 1
Symbols evaluate to whatever value is associated with the symbol, thus
> pi 3.141592653589793but
> z Error: The variable Z is unboundsince, in this example, the symbol
has not
been defined. To define a symbol, we could
do something like this, where we define
e to be 
> (def e (exp 1)) E > e 2.718281828459045The first ``E'' is echoed by the interpreter, which is case-insensitive. At the next prompt, we typed the symbol, and the interpreter responded by printing its value.