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GEURTS & L . G . L . T . MEERTENS DESIGNING A BEGINNERS' PROGRAMMING LANGUAGE

P re p u b l i c a t i o n

2e boerhaavestraat 49 amsterdam

Ptinted a t the Mathematicat Centte, 49, 2 e 80ethaaye4i2aat, Amstetdam. The Mathematicat Centte, punded the 11-th 06 Febtuaty 1946, i.40 a noniniotitation aiming a t the pumotion 04 puke mathematic4 and 4.t6 appti_co-ti_ono. L t 0 0 n 4 0 t e d by the NetheAtand6 Govetnment thtough th e NetheAtand6 0Aganization 6 0 t the Advancement o6 Pute Rezeatch (Z.W.0), by the Municipatity 06 Am4tetdam, b y the Univetsity 06 Am6tetdam, b y the F e Univeu-Lty a t Am6tetdam, and by i n d a ztti e s.

AMS(MOS) s u b j e c t c l a s s i fi c a t i o n scheme (1 9 7 0 ): 6 8 A 3 0

ACM—Computing Re vie ws—ca t e g o rie s: 4 . 2 2

De s ig n in g a b e g i n n e r s ' p ro g ra mmin g la n g u a g e by

L . J . M. G e u r t s & L . G . L . T . Me e rt e n s

ABSTRACT

FORTRAN : ALGOL 6 0 = P L / I : ALGOL 6 8 = BASIC : ?

KEYWORDS & PHRASES: pr ogr amming language, s t r u c t u r e d programming, pr ogr am-

ming language design, s i m p l i c i ty

*)

Th is p a p e r i s n o t f o r r e v i e w ; i t i s me a n t f o r p u b l i c a t i o n e lse wh e re

O. INTRODUCTION

Among pr ogr am m i ng l a n g u a g e s t h e r e i s a f a m i l y o f l a n g u a g e s w h i c h a r e c h a r a c t e r i z e d by t h e i r s y n t a c t i c and s em anti c s i m p l i c i t y and t h e i r s u i t a b i l i t y f o r c onv e r s a t i o n a l u s e . P e r h a p s t h e m o s t f a m i l i a r o f t h e s e i s B A S I C , s om e o t h e r s b e i n g FOCAL, J OSS a n d TELCOMP. T h e t y p i c a l u s e r o f s u c h l a n g u a g e s i s n o t a p r o f e s s i o n a l pr ogr am m er , n o r d o e s h e d w e l l i n a n ac adem i c c o m p u t e r s c i e n c e e n v i r o n m e n t . H e does n o t h a v e t h e t i m e n o r t h e a m b i t i o n t o l e a r n a c o m p l i c a t e d l a n g u a g e f o r t h e oc c as i onal pr ogr am he w r i t e s . Now, t h e s e l a n g u a g e s w e r e m o s t l y d e s i g n e d b e f o r e t h e c u r r e n t i d e a s o n " s t r u c t u r e d " pr ogr am m i ng bec am e g e n e r a l l y a c c e p t e d . T h e y l a c k m o s t o f t h e t o o l s t h a t a pr ogr am m i ng l a n g u a g e c a n p r o v i d e f o r t a k i n g a s t r u c t u r e d a p p r o a c h t o pr ogr am m i ng, p r e s u m a b l y b e c a u s e a b o u t t h e s am e e f f e c t s c o u l d b e o b t a i n e d w i t h " s i m p l e r " m eans . U n f o r t u n a t e a s t h i s i s b y i t s e l f , t h e s i t u a t i o n i s p a r t i c u l a r l y b a d s i n c e , f o r e x a m p l e , B A S I C - m ay be t h e w o r s t v i l l a i n i n t h i s r e s p e c t - i s q u i t e com m onl y us ed t o t e a c h h i g h s c h o o l s t u d e n t s i n t r o d u c t o r y c o u r s e s i n c om put er s c i e n c e . T her e e x i s t s l i t t l e m a t e r i a l o n t h e e f f e c t o n a pr ogr am m er o f t h e fi r s t pr ogr am - .

m i ng l a n g u a g e h e i s e x p o s e d t o , b u t f r o m p e r s o n a l e x p e r i e n c e w e h a v e t h e s t r o n g i m pr es s i on t h a t i n m any c a s e s i t d e e p l y i n fl u e n c e s h i s t h i n k i n g h a b i t s f o r a l o n g ti m e t o c om e. I t i s o u t o f c onc er n w i t h t h i s s i t u a t i o n t h a t w e hav e l ook ed a t t h e pr obl em o f d e s i g n i