The standard version has more stack space, allowing bigger programs or in general giving the interpreter less reasons to crash than the one providing graphics
It's better to elaborate on what this CLiSP is and what it is not.
First of all, the Campus LIsP is a limited subset of the LISP language.
The reason for its existence is to teach how this kind of interpreter works and the programming basics for it, thus it is intentionally minimalistic, the LAMBDA declaration was intentionally excluded. ('lambda" is a crucial LISP keyword and we are not supporting it on the LAMBDA !)
Such dramatic simplification allows it to run it on a small computer. z88dk and a bit of crazy tricks did the rest.
By the way a 16K version in theory should't even boot!
It does at a high price, the 'atom' size is very small and the algebraic computation do easily overflow. I also reduced the (already minimal) number of predefined functions, but the missing ones can still be recreated in LISP:
; factorial, minimalistic mode example
(defun fact (n)
(cond ((< n 1)
1)
(t
(* n (fact (- n 1))))))
; print
(defun print (n) (progn (terpri) (princ n)))
; zero?
(defun zerop (n)
(eq n 0))
; greater than or equal to?
(defun >= (n1 n2)
(or (> n1 n2) (= n1 n2)))
; less than or equal to?
(defun <= (n1 n2)
(or (< n1 n2) (= n1 n2)))
; eq?
(defun = (n1 n2)
(eq n1 n2))
; increment
(defun 1+ (n)
(+ n 1))
; decrement
(defun 1- (n)
(- n 1))
; remainder
(defun % (a b) (- a (* (/ a b) b)))
; sum
(defun sum (n)
(cond ((< n 1)
0)
(t
(+ n (sum (- n 1))))))
; power
(defun power (x n)
(cond ((< n 1)
1)
(t
(* x (power x (- n 1))))))
; equal
(defun equal (s1 s2)
(cond ((atom s1)
(eq s1 s2))
((not (atom s2))
(and (equal (car s1) (car s2))
(equal (cdr s1) (cdr s2))))
(t
nil)))
The idea of the turtle graphics functions was borrowed from SpecLISP, a good but buggy interpreter for the ZX Spectrum. I fixed some of the bugs on it too, but it is another story.
Besides the graphics, the syntax in Campus LIsP is very close to Common LISP (SpecLISP had a slightly different syntax, which I chose not to use here, but it's very easy to retrofit the Campus LIsP for anybody feeling nostalgic).
The available memory won't allow you very much, it's a bit like trying to type useful programs on a 1K Sinclair computer! I 'm sure you all get the point and understand it still can be fun.
SAVE and LOAD are not supported, but nowadays a snapshot in the emulator can help in freezing your environment and progress with your experiments later