Brusilovsky, P., Calabrese, E., Hvorecky, J., Kouchnirenko, A., and Miller, P. (1997) Mini-languages: A Way to Learn Programming Principles. Education and Information Technologies 2 (1), pp. 65-83.

Peter Brusilovsky

School of Computer Science, Carnegie Mellon University,

Pittsburgh, PA 15213 USA

plb@cs.cmu.edu Eduardo Calabrese

Dipartimento di Ingegneria del l'Informazione,

University of Parma, 43100 Parma, Italy

educal@ce.unipr.it Jozef Hvorecky

University of Economics, 832 20 Bratislava, Slovakia

hvorecky@vseba.sk Anatoly Kouchnirenko

Department of Mathematics, Penn State University

University Park, PA 16802 USA

agk@math.psu.edu Philip Miller

School of Computer Science, Carnegie Mellon University,

Pittsburgh, PA 15213 USA,

plm@cs.cmu.edu

Abstract: Mini-languages are a visually intuitive, simple, and powerful way to introduce students to programming. They are a good foundation for general computer science instruction, provide insight into programming for the general population, and teach algorithmic thinking. The goal of the paper is to provide an extensive review of the mini-language approach to teaching programming. For different audiences and in different countries, the authors have extensive experience in design and application of mini-languages. We outline the problems which motivate the application of this approach, present a brief history, review several existing mini-languages, and provide discussion of lessons learned. In particular, we discuss how to choose a mini-language for a particular group of students and list some requirements for a successful application of a mini-language. We conclude with a discussion of possible future directions of the mini-language approach development.

There have been many efforts to develop special languages for supporting the initial steps in programming education as an 'easy start' for novices (Mendelson, Green, & Brna, 1990). Genuine insight was given by the "turtle graphics" of Logo (Papert, 1980). The success of Logo in general and turtle graphics in particular stimulated the development of the mini-language approach to teaching the principles of programming.

The idea of the mini-language approach is to design a small and simple language to support the first steps in learning programming. In most of the existing mini-languages a student learns what programming is by studying how to control an actor, which can be a turtle, a robot or any other active entity, acting in a microworld. Although an actor can be a physical device, the student usually deals with a program model of such a device and observes the behavior of the executive on a screen. The actor can perform small set of commands and answer several value-returning queries. Usually the student controls the actor first by giving isolated commands and then by writing small programs on a special miniature programming language. This miniature language includes commands and queries of the actor and several control structures[1]. In this paper we use the term mini-language to name a combination of an actor with a language to control it.

There are multiple worthwhile objectives for teaching mini-languages. Mini-languages can provide a solid foundation for learning a general purpose language such as Pascal, C, or LISP. Mini-languages also provide a sound basis for systematic problem solving for people who will program only to customize their spreadsheet, database, or CAD package, or another application program. Mini-languages open a door to new educational opportunities. Regardless of the student's eventual penetration into programming and regardless of the age of the student, there is a positive residue of the study of a mini-language. It is the acquisition of algorithmic thinking as an explicit, familiar and powerful tool.

This paper provides a review of the mini-language approach. We outline the problems which motivate the application of this approach, present a brief history of the approach and a review of existing mini-languages and provide an extensive discussion of lessons learned. In particular, we discuss how to choose a mini-language for a particular group of students and list some requirements to a successful mini-language. All authors have a deep, positive experience in the design and application of mini-languages for different audiences in different countries. Our suggestions are based on experience of teaching hundreds and thousands of real students. We conclude with a discussion of possible future directions of the approach development.

Nowadays, most of the students who start to learn the principles of programming are taught by the old classic approach. This approach is based on using a general-purpose programming language such as Pascal, Modula-2, LISP, or C, a professional programming environment for the chosen language, and a set of problems from the area of number processing and symbol processing. We believe that the effectiveness of the classic approach is quite low in general, and the younger the students the worse the classic approach works. In particular, using general-purpose languages creates the following three kinds of obstacles for novice programmers:

General-purpose languages are too big and too idiosyncratic. The conceptual basis of the language together with the main principles of programming combine to form a large amount of material. This volume alone makes it difficult to understand the material properly, thereby failing to form a strong cognitive infrastructure. Instead of emphasizing fundamental principles, the languages evoke secondary notions which reflect the subtleties of the given language and its implementation. General-purpose languages provide little leverage for understanding their basic actions and control structures. The languages are not visual and their basic functions are carried out behind an opaque barrier. Professional programming environments usually don't provide any visualization capabilities. With the process of program execution hidden, the student develops an input-output oriented understanding. In this way the absence of visual feedback hampers mastery of language semantics. Since general-purpose programming languages are oriented on number and symbol processing, the first possible problems used in teaching the language are far from the students' everyday experience and are not attractive for them. Developing applications that are both informative and interesting requires learning a considerable language subset and writing quite a big programs, and this introduces another distraction - the need to master the programming environment. As a result, the first, difficult steps in learning to program are usually neither well motivated nor supported by work on the computer.

There are two reasons why mini-languages are a good alternative. One is that they provide a good foundation for general computer science instruction. The other is that they open a door onto new educational opportunities. We believe that principles of computer programming is a topic which should be learned starting at the early stages of school. It provides the basis for logical and abstract reasoning which is fundamental to the learning process.

The first advantage of mini-languages is, as the name suggests, that they are small. Mini-languages have a small syntax and a simple semantics. A student, even a very young one, can thus come to grips with the entire mini-language and employ it with interesting results. In the words of Seymour Papert, students can "expropriate" the mini-language, making it their property. The time required to master a mini-language itself is small, so the students can spend most of their efforts on more important issues: mastering algorithm development and program design in a university setting or understanding the principles of programming for a more general audience.

A second important advantage is that mini-languages are built on metaphors that are intrinsically engaging and visually appealing. It is possible to create rich sets of problems that both cover the fundamental ideas and dovetail with the students life experiences. This causes students to want to expropriate a mini-language.

The operations performing by the actor are always naturally visible revealing the semantics of language constructs. Visual queues enable the novice to understand semantics of introduced constructs, elucidate principles of program structure and execution. protecting them from developing misconceptions. Visibility provides a feedback for exploratory learning and problem solving. Visual metaphors make it easier to develop interesting problems for important concepts. Problems that achieve visible and meaningful results aid concept mastery by reinforcing them with problem solving activities.

Another important advantage is that the designer of a mini-language is not restricted to the syntax and semantics of any "big" language, which may not be suitable for novices. As a language designed especially for an educational purpose and for a well defined audience, a mini-language can take advantage of the narrow definition of the class of its users by using students' native language for keywords and providing only data types and control structures essential for these students. In the same way, the designer of a programming environment for a mini-language can take advantage of the small size and known audience of the language and design a highly attractive and effective environment.

The development of the mini-language approach was seriously influenced by turtle graphics of Logo (Papert, 1980). In some sense, the turtle graphics set can be considered the first example of a mini-language. Logo was not designed especially for the purpose of teaching programming but the "turtle subset" appears to be a good tool for introducing programming to novices, and it strongly contributes to the overall incredible success of Logo. Logo provides genuine insight for further development of mini-languages, however Logo turtle graphics is not the best example of mini-language. Note that unlike most of the actors of mini-languages described below, the turtle of Logo is "blind", it can't check its microworld. The "turtle subset" also does not support such classic control structures as Pascal-like if and while . To introduce these constructs the language needs to contain some predicates which provide feedback when controlling the actor.

The first and still the most popular real mini-language Karel the Robot was designed by Richard Pattis as a "gentle introduction" to Pascal for university students taking their introductory programming course. Karel the Robot was completely described in a book with the same name (Pattis, 1981) written by Pattis, who also designed the first programming environment for Karel. Karel contains all important Pascal-like control structures and teaches the basic concepts of the notions of sequential execution, procedural abstraction, conditional execution, and repetition. The overhead of full high level programming languages is reduced as there are no variables, types or expressions in Karel. The actor, robot Karel, performs tasks in a world that consists of intersection streets and avenues, walls, and beepers. Karel can also carry some beepers in his "bag". The main actions of Karel are move , turnleft , pickbeeper , and putbeeper . A set of 18 predicates allows Karel to check the state of his microworld. For example, Karel can determine the presence of nearby walls, if there are any beepers in his bag or at his location, and the direction he is facing. By writing programs that cause Karel to perform carefully selected tasks, students gain experience with the fundamentals while using a pleasant and persuasive metaphor.

Karel the Robot has been very important both as a mini-language and in stimulating other work. The following are several mini-languages that were directly inspired by Karel and use some of its features: Martino (Olimpo et al., 1985) and Marta (Calabrese, 1989) in Italy, Darel (Kay & Tyler, 1993) in Australia and Karel-3D (Hvorecky, 1992) in Slovakia. Original Karel the Robot is now in use in many universities and colledges in USA. A new edition of the Karel the Robot book has been issued recently (Pattis, Roberts, & Stehlik, 1995).

Figure 1: Karel the Robot

Karel-3D (Hvorecky, 1992) is an extension of the idea of Karel the Robot. Karel-3D expands original Karel into several directions to make it more suitable for special audiences such as preschool students or secondary school pupils.

The robot can move in the 3-dimensional space displayed in a separate window. Other windows are used for typing programs, for menus and for context-sensitive help.

The robot can lay a brick, stand on it and (as a result of repeated actions) to move up and down. Thus, the movement of the robot is also "three-dimensional'".

The robot obeys either pressing keys (in a steering or navigation mode) or commands (in a programming mode). A family of languages is created in this way. Small children use steering, older ones start with programming.

Many Czech and Slovak schools use Karel-3D as their first (and sometimes the only) programming language. Karel-3D is supported by a textbook (Gasparovicova & Hvorecky, 1991).

Figure 2: Karel-3D

Marta (Calabrese, 1989) is a screen robot based on Logo and is similar to the robot Karel. It can be used as a soft introduction to programming from pre-school age to adults. Being written in Logo, Marta offers the following advantages over Karel:

Marta can be driven in navigation mode with single keystrokes which makes it suitable even for preschool children,

Marta can build her world since she can put or remove walls,

Marta can be driven in the dark where the obstacles and beepers are not visible although they are still there,

new commands and operations can easily be defined by writing Logo procedures,

several levels of programming are available: one-line programs, multiple-line programs, and Logo procedures.

The only limitations with respect to Karel are that Marta's world is bounded to a 7x15 grid and that she cannot put down more than four beepers at an intersection.

Some mini-languages were designed independently of Karel but with some influence of Logo. One example is Josef the Robot (Tomek, 1982; Tomek, 1983) designed by Ivan Tomek. Josef was designed at the same time as Karel and its philosophy is a combination of Logo and the ideas used in Karel namely the idea of a rich microworld of Logo and the idea of preparing the user for programming constructs of conventional languages as in Karel. Josef provides a relatively rich microworld - a robot living on the screen and capable of graphics and other operations, particularly in a simulated real world represented by a map. It uses constructs similar to conventional languages and advanced concepts such as interrupts. One of the features intended to avoid syntactic difficulties that obscure the essential concepts of problem solving by programming is that variables and procedure arguments are untyped.

Several mini-languages were designed and used widely in the USSR where the book of Pattis was not available. Three of them are Wayfarer, Turingal, and Tortoise. Some more information about Russian mini-languages can be found in (Brusilovsky, 1990).

Wayfarer was suggested in 1980 to support a new course on programming for the students of the Mechanics and Mathematics department of the Moscow State University (Kouchnirenko & G., 1988). The goal was to challenge the students from the first lesson with a set of interesting problems. This set of problems concentrated on the task of controlling a simple actor "Wayfarer" moving on a checked field with walls. The solutions were written in a simple mini-language called MINI containing if-then-else and while-do statements, procedures without parameters, commands and queries to an actor. Several years of experience proved that 4-6 weeks of work with Wayfarer give the student a solid ground for the study of general notions of programming.

The Turingal mini-language (Brusilovsky, 1991) was designed in 1983 for computer science students of the Moscow State University. This language is a way to control the well-known basis of algorithmic theory - the Turing machine which works with a tape of symbols. The elementary operations of the mini-language are simple and visual: the movement left and right along the tape and typing the symbols on the tape. To control the machine, Turingal offers a set of control structures (conditional statement, loops, case) and subroutines, with syntax and semantics similar to the structures of PASCAL (Turingal = TURING machine + pascAL). One of the main reasons for presenting the mini-language is to bring the student to the mastery of the semantics of these well-known structures before starting to learn Pascal.

The Tortoise mini-language was designed to support a part of the computer literacy course for 14-15-year-old students in Russian schools. It is similar to the Turingal, but adds some features which make it attractive for younger students. For example, the tape of symbols was substituted by a two-dimensional field of symbols.

After more then ten years from the appearance of mini-languages it's the time now to summarize some lessons learned. The authors of this paper have had positive experience using different mini-languages in different countries for different audience. Comparing and analyzing our experience can draw some generalizations. This section discuss several aspects of mini-language development and application.

The mini-languages applied by the authors of this paper are designed for different age groups, ranging from elementary school students (Marta and Karel-3D), through secondary school ages (Tortoise and advanced versions of Karel-3D) to college freshmen (Wayfarer, Turingal and Karel). All authors reported success in engaging their audiences and in teaching problem solving and fundamental principles. In this sense the mini-language approach is a kind of "silver bullet" which gives good results in teaching the principles of programming for different audiences.

At the same time there is no "right" or perfect mini-language. There are different mini-languages and they suit different needs, because the type of an actor and the set of mini-language control structures depend on the age, background, interests and learning goals of the student. For example, when one of the authors tried to redesign the Turingal mini-language environment used previously in the university for school students who were three years younger, he had to redesign the executive and the microworld as well. The Turing Machine executive with a one-dimensional tape microworld which was used in the Turingal mini-language does not seem to be interesting for the majority of 14 years old students who never had a course on the theory of algorithms. The new mini-language called Tortoise adds two-dimensional world, color and sound to the classic Turing machine to make the microworld attractive for these students.

Another example shows that an actor can be extended to accommodate the extended learning goals. Several years ago the paradigm of actor-executive supported originally by the Wayfarer was applied in secondary school course Foundations of Computer Science and Technology (Kouchnirenko, Lebedev, & Svoren, 1993). The main idea was to use executives to motivate the introduction of variables, arrays, and simple calculation procedures. To support it the Wayfarer was replaced by a more powerful executive Robot in a richer microworld. For example, Robot can measure the "temperature" and "radiation level" at the current position of the field.

The audience can differ in the overall goal of using the mini-language. There are two main reasons to apply the mini-language approach. First reason is to support an introductory computer science course in a university setting. Here a mini-language can be used to provide a "gentle introduction" into one of the general purpose programming languages (Pattis, 1981) and to support mastering such general skills as algorithm development, program design, and program debugging (Comar & Pintelas, 1989; Ferguson, 1987; Kay & Tyler, 1993). Second reason is to support the language-independent learning of the principles of programming and algorithmic reasoning (Brusilovsky, 1991; Gasparovicova & Hvorecky, 1991; Olimpo et al., 1985). In the early stages of mini-language application the first goal dominated. At present, the second goal has become more important as the principles of computer programming is a topic which should be learned widely (and probably at the early stages of school), since it provides the basis for logical and abstract reasoning which is important in any learning process and everyday life.

Note that the application of a mini-language is never the goal itself, but a method of mastering a set of notions and skills. If this set contains not only programming concepts, but also some concepts from another domain, a mini-language might be useful to learn this domain (as Logo is used to learn geometry). There is, for instance the mini-language SOLO aimed at the student of psychology (Eisenstadt, 1983).

Some features of mini-languages are important for success. The mini-language should be simple in both its syntax and semantics. Simplicity is essential - see the classic paper (du Boulay, O'Shea, & Monk, 1981) for the discussion of simplicity. The mini-language should be naturally visible most operations performed by the actor should make visible changes in the microworld represented on the screen. The mini-language should be attractive and meaningful for the intended category of students. A good example for it is Japanese Algo-Arena (Kato & Ide, 1993) mini-language system applying the metaphor of Sumo wrestling, which is meaningful and appealing for young Japanese students, or another system (Comar & Pintelas, 1989) applying the metaphor of shopping in supermarket.

The above requirements stem from the very idea of a mini-language. Other desired features are not so obvious and stem from experience. The mini-language should be conversational as Basic or Logo. It means that any mini-language command can be executed in both navigation mode (single command execution) and programming mode (complete program execution). Our experience shows that immediate execution and navigation modes are important for young audience. The original Karel did not support a navigation mode, but both extensions of Karel for primary and secondary school students, Karel-3D and Marta, add this feature.

A mini-language should be modular language. It should contain a mechanism for creating abstract instructions (procedures). All the procedures should be independent units. Such a procedure can be considered as a new command of the actor, which can be used in both navigation and programming mode.

The procedures designed for a particular problem can be later re-used for solving subsequent problems. Logo, Karel, Josef and Wayfarer provide good examples of modular languages.

An important lesson is that selecting a mini-language approach is not enough for successful teaching the principles of programming. The learning should be supported by a good programming environment. Such an environment should keep both the microworld and the student program visible on the screen. The program should typically be executed one instruction at a time, while the interpreter highlights programming constructs in the source code as they are being executed and the effect is simultaneously shown in the microworld. This makes the connection between a mini-language command or construct and its effect on the microworld obvious. The interpreter should also provide visualization for those concepts of the language that are not visualized by the microworld. Important features include visualization of variables and the stack of subroutine calls.

The environment should also provide a structure editor, to increase student productivity, and enable the student to concentrate on the more important parts of problem-solving. The structure editor protects the student from making most syntax errors and provides immediate diagnostics for the remaining ones. Providing menus or hot keys, the structure editor also solves the contradiction between the requirements to enter the constructs easily and giving them meaningful names. A related useful component of the environment is a graphical program design tool. Such a tool makes the program structure visible and understandable for the student.

A good example of a mini-language programming environment with all the desired features is provided by Karel Genie (Miller et al., 1994) a novice programming environment for the Karel mini-language.

To support the novice programmer, the Karel Genie provides a set of specially designed tools, which include a structure editor, a program decomposition view for both looking at and editing programs, and a runtime system with advanced visualization tools. The Karel Genie is an integrated programming environment. Editing the program, executing the program and taking a high level view of the call structure are all presented within a single user-interface, allowing students to move from one activity to another with little cognitive overhead. Karel Genie structure editor provides maximum support to the novice programmer since program construction can be conducted entirely through menu interaction. As novices develop expertise they begin to exploit Karel Genie's text edit features. The Karel Genie graphical program design tool lets students decompose a problem into simpler sub-problems by dragging the mouse from the program root.

Karel Genie is highly visual and successfully uses multiple representations. This is clearly illustrated in Karel Genie's runtime system. Code is highlighted as it is executed. At the moment a "move" is executed in the code window, a Karel icon moves in the world. Selection, repetition, and recursion are similarly visually reinforced. This is extremely valuable in teaching basic concepts as well as in introducing powerful and "advanced" concepts such as loop invariance. Karel programs can be single stepped and run either forward or backward. The runtime environment also has a visual call stack. This makes procedure invocation and return clear.

Figure 3: Karel Genie: Editor + Design View Used + Run Time with Tracing Call Stack

The Karel Genie has been in use in secondary schools and universities throughout the US for nearly ten years. In addition to CMU it has been used in computer science classes at Harvard University, New York University, Stanford University, Swarthmore College, Ohio State and a number of other institutions.

Thus a good mini-language is important, but not enough for success. A programming environment is very important too. In particular, just applying the Logo language with its famous Turtle graphics for teaching programming is often not enough. In recent papers, Logo authorities argue the importance of extended programming environments for Logo with variable visualization, stepwise execution, and even a program design tool (da Rocha, 1993; De Corte, 1993). We should note that most of recent successful mini-language environments (Karel-3D, Tortoise, KuMir) include both a structure editor and a runtime system with extended visualization. For example, in Karel-3D the text of any program can be created as a combination of commands and tests taken from menus. Problems that children have with typing are avoided this way. The programming mode contains various debugging and visualization tools. The execution of a program can be slowed down or speeded up, if necessary. The executed commands can be highlighted.

A good mini-language should be complemented with a good set of attractive and meaningful problems for students to solve. Problem solving is the most effective way of mastering the mini-language and, consequently, supporting important concepts. The set of problems must contain the problems of various complexity (be ready also to challenge top 10% of your students with attractive but difficult problems) and cover all important concepts. These problems must be interesting for the student both from the point of the goal to be achieved, and the process of solution development. Sometimes these problems look as a puzzle rather than a 'serious' programming task and the problem-solving activity becomes a kind of a game. We recommend keeping the set of attractive problems in mind when designing a mini-language. A mini-language that looks very attractive but for which a sufficient number of problems are not available looses its attractiveness very quickly. Often the choice of an actor is driven by the goal of making the set of problems the student is expected to solve attractive and meaningful. Compare, for instance, two problems:

(a) For given matrix A find some pair (i,j) such that A(i,j)=0;

(b) Move Robot to some position where radiation level is equal to zero.

The mini-language augmented with a good set of problems can support problem-driven learning, when the student is presented with a new meaningful problem and a new language construct is then introduced which helps to solve the problem. This approach has been used fruitfully in the textbooks (Kouchnirenko & G., 1988; Kouchnirenko, Lebedev, & Svoren, 1993).

The above considerations concerns traditional minilanguages which can be described as "one microworld - many problems". There is however an opposite approach "one microworld - one problem", where the microworld is oriented on solving one, though difficult, problem, like finding an exit from a labyrinth. A good example of it are TRAPS (Witschital, Stiege, & Kuehme, 1989) system where the task is to move an actor through the playing board filled with various obstacles, and Algo-Arena (Kato & Ide, 1993) where the task is to control a Sumo wrestler. Here the student learns to program by solving more and more complex subproblems of the problem, or solving the problem for more and more complex configuration of the microworld as in TRAPS, or designing more and more complex and better program solutions as in Algo-Arena. A limited set of problems in these systems is compensated by an attractive and meaningful microworld. We think that the systems of this kind can be suitable to support a small course on the principles of programming for a young audience.

Several mini-languages with different actors can be used sequentially or simultaneously in an introductory programming/design course for computers science university students. It can be several regular mini-languages (Kouchnirenko & G., 1988) or several one-problem mini-languages as suggested in (Comar & Pintelas, 1989; Ferguson, 1987). Different microworlds can be used to stress different aspects of the subject (for example floating point numbers) or to teach different parts of it. Here the problem is that understanding of a new mini-language requires considerable amount of time and mental efforts. The application of any additional mini-language should be justified. Two lessons learned from the experience are: once started to use a mini-language the student expected to use it for a considerable amount of time; the miniature languages to control different actors should be similar (at least should have the same control structures).

An approach very similar to the mini-language approach is the sub-language approach. The idea of the sublanguage approach is to design a special starting subset of the full language containing several easy to visualize operations. Such a subset can support the first steps of learning programming and helps later in introducing more complex programming concepts. The sub-language approach was also influenced by the turtle graphics of Logo. A set of four "turtle" commands of Logo provides the first example of a sub-language. Usually the sub-language approach applies the same idea of an actor in a microworld, and the starting subset is really a set of commands and queries performed by the actor. Moreover, the same kind of actor can be controlled by a mini-language, or by a sub-language.

The sub-language approach differs from the mini-language approach in one important feature. While the mini-language approach uses a special miniature language with its own commands and control structures, the sub-language approach provides only a set of commands and queries as an extension of some "big" programming language. These commands and queries are used in combination with standard control structures of the "big" language. A good experience in designing sub-languages has been accumulated in Russia. The programming environment KuMir which supports the Russian secondary school course on "Foundations of Computer Science and Technology" (Kouchnirenko, Lebedev, & Svoren, 1993) applies several interesting actors (each one can be considered as a sublanguage) within the same educational programming language (E-language).

KuMir is an integrated educational environment, combining a text editor with zero-response-time incremental compiler and a simple debugger. The basic philosophy which governs KuMir is that the language has a compact core which can be dynamically extended by loading one or more separately prepared modules--executives providing new microworlds and actors, or even new numerical packages and abstract types of data. This approach allows easy customization of the system. The school teacher can start with one of the traditional actors like Robot then add more sophisticated options (Kouchnirenko, Lebedev, & Svoren, 1993). On the university level the special packages like complex and rational numbers or plane geometry can be added. During the last three years KuMir has been used at the Department of Mathematics of Moscow State University in support of undergraduate courses of mathematics.

We think that the sublanguage approach is often better when the student's direct goal is to learn a particular big language. The student can learn most of the control structures and operators of the language more easily with the help of the visible subset. However, if the goal in not to learn a particular language but to learn the principles of problem solving by programming which can later be followed by learning a "real" language, the mini-language approach is better. Using sub-languages can be recommended for the university introductory programming courses. Here the sub-language approach can be successfully combined with using several actors for different purposes (as in KuMir).

This paper discusses only the approaches related with teaching procedural paradigm languages. The mini-language approach however can be applied successfully with other paradigms. An example of applying the mini-language approach for teaching parallel programming paradigm is the Robot Brothers project (Olimpo, 1988). Three good examples of mini-languages designed to support object oriented paradigm are Playground (Fenton & Beck, 1989) and Gravitas (Sellman, 1992), and KidSim (Smith, Cypher, & Spohrer, 1994). The latter mini-language can also serves en example of learning some physics concepts (laws of gravitation) along with the principles of programming, and as an example of how to design an attractive mini-language for a particular category of students. Several authors consider object-oriented mini-languages as most natural and suitable way to teach introductory programming and "control technology" to younger students (Kato & Ide, 1993; Resnick, 1990; Whalley, 1992).

When teaching the principles of programming for a very young audience of 7 to 9 years old, special attention should be paid to the attractiveness of an actor. A good way to make an actor attractive for young students is using a real world actor - some real computer controlled device as the first "real turtle" of Logo. A good step towards real world actors is done by robotic toys as Lego - Logo. Robotic toys can provide good motivation to learning for a very young audience. The authors think this is an area that should receive more attention. Special work has to be done to make real world actors not only attractive, but also really useful in learning general concepts. In particular, robotic toys can be naturally applied to support learning the object-oriented paradigm. Some encouraging results in this area were reported recently (Whalley, 1992). Another example is the use of robotic toys by a concurrent extension of Logo called MultiLogo to teach the principles of concurrent programming (Resnick, 1990). Interesting results in making "real world programs", i.e. constructing a program as a real world artifact assembled from modules are reported in (Kato & Suzuki, 1993). Real world actors and real world program are not only more attractive, but also support collaborative problem solving activity.

A promising way of further development of mini-language programming environments is to extend it with intelligent tutoring component and hypermedia component. Intelligent tutors have shown impressive results in mathematics and programming. By connecting intelligent tutoring to mini-languages it is conceivable that learning can be improved by an order of magnitude. Intelligent computer tutors can decrease the amount of non-creative work of the human tutor and reserving the teachers time to work with students who have special needs. Intelligent tutoring components provide the required amount of guidance: suggest the next concept to learn or the problem to solve according to the student's current knowledge, assist the student in the problem solving process, diagnose the student's solution. First examples of creating an intelligent tutors for mini-languages were reported in (Brusilovsky, 1992; Dion & Lelouche, 1988; Witschital, Stiege, & Kuehme, 1989). The hypermedia component extends the space of exploratory learning, providing student-driven access to conceptual knowledge and examples. Recently a hypertext component was designed for KuMir programming environment and the hypertext electronic version of the textbook (Kouchnirenko, Lebedev, & Svoren, 1993) is now under development. Some ideas about integration of a programming environment, a hypermedia component, and intelligent tutoring systems into a single system can be found in (Brusilovsky, 1993).

All the authors of the paper, i.e. five university teachers, representing four different nations, using similar - but distinct mini-languages report positive results from using mini-languages. However all our findings and recommendations are results of experience rather then rigorous empirical evaluation. It is time to investigate such claims empirically and report the findings. There are very few papers at present that report any results of classroom studies or special experiments with mini-languages. For example there was special empirical evaluation to study how skills learned in Karel are transferred to other problem solving settings (Scheftic & Goldenson, 1986), or how the visual nature of the Tortoise minilanguage helps student in debugging their programs (Brusilovsky, 1994). We believe it would be of great value to the larger educational community to study the mini-languages in a rigorous and repeatable way.

Much research and development work have been done in the field of teaching introductory programming and a number of powerful environments have been created. Teaching programming to beginners was often used as a testbed to apply new creative ideas about how programming should be taught. It is time now to transfer these ideas and experience to "real life" in the following two senses. First, these excellent novice programming environments should leave laboratories and universities where they have been developed and find their way to schools, universities and homes. Here the role of software companies is important. Good examples are the Karel Genie and KuMir which are both used widely outside the place they were developed. But even here additional efforts are needed to turn these environments into programming products that can be bought in a store. Second, current "big" programming environments such as Borland Pascal should learn some lessons from best novice environment experience. Although current programming environments provide debuggers operating at source code level and capable of step-by-step execution with display of current data values, they still lack many useful features that exist in the environments we have described above. Good examples of programming environments for professional languages that have most of the required features discussed above are Pascal Genie (Miller et al., 1994) from Carnegie Mellon University and PascalMir and FortranMir from Moscow State University.

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Footnotes

[1]

Most mini-languages include all basic control structures (conditional execution, looping, recursion, etc.) and a mechanism for creating new instructions (or other kind of sub-programs).