The Use of Apple Macintosh Computers In Teaching at ETH Zurich

The Use of Apple Macintosh Computers
In Teaching at ETH Zurich
By A. VENTURA, W SCHAUFELBERGER, aqd A. FISCHLIN Project-Center IDA, ETH ZU n ch
Abstract
Several hundred Apple Macintosh computers are
used in teaching at ETH. First, an overview on the
different ways these computers are currently used is
given. Then, some examples of educational
programs are provided, and the "DialogMachipe",
an authoring system developed at ETH, is
presented.
Introduction
Macintosh and IBM compatible computers are the
main lines of PCs used in teaching at ETH. Lilith,
Ceres, Sun and VAX are strongly represented in the
workstation and midi range. The decision about
what kind of computer to use in teaching is left to the
individual faculty member.
The Institute for Informatics decided early to use
the Apple Macintosh for the general two-term
introduction to computer science provided in most
departments. About 300 Macintosh Reflex are used
to introduce about 1500 students to the basics of
computer programming each year. The fast
Modula-2 system MacMETH (Wirth et al., 1986) is
used mainly for this purpose, but MacPascal is also
available. Several faculty members from different
departments got interested in using and extending
this infrastructure of computer-based teaching.
In the Department of Architecture, Macintosh
computers are mainly used for architectural
drawing and calculations (Kramel et al., in
Schaufelberger (1988a)). In the introductory
courses to Technical Mechanics, all exercises are
available on floppy disks (Sayir and Kaufmann, in
Schaufelberger (1988a)). Mathematicians use
computers for numerical and symbolic
calculations. A set of programs for the basics of
computer science, for systems analysis in natural
sciences, and for control engineering have been
developed by the current staff of the IDA Center
which is responsible for the school-wide
coordination of the use of computers in teaching.
Some examples will be provided in the follewing:
Introduction to Computer Science
One of the main problems in teaching the basic
algorithms of computer science is the purely static
notation on blackboards or overhead projectors.
The teacher usually plays the role of the machine
executing the algorithms manually. This is a
difficult task, prone to errors. Animation of
algorithms by computers with good graphics
possiblities on the other hand, is an easy task. The
programs can be used for classroom demonstration
and for individual exercises carried out by the
students. With this in mind, a set of very easy to use
programs has been created, treating the following
subjects:
- Sorting algorithms
- recursion and iteration with graphics
- real arithmetics
- random number generation
- recursion
Fig. 1 shows the commands available to move
through the sorting algorithms, and a typical screen
out of the program is represented in Fig. 2.
For further details, see V en tura & Goorhuis (1987),
and Ventura & Schaufelberger (1988).
Systems Analysis in Natural Sciences
Students in agricultural engineering and natural
sciences are introduced to systems analysis in their
2nd and 3rd year. They learn to model dynamic
19
In: Wheels Europe, No.2, 1988, 19-26

.,
folgende Seite
uorhergehende Seite
Programm beenden
Des Array wi rd nach fol 9
Wert
E i n fii h ru n 9
Array uorbereiten
Sor ti.ru.r tahr.n
Bubblesort: sortieren durch Rustauschen
Shaicersort
Selectionsort: sortieren durch Ruswahlen
Shellsort
Heapsort: sortieren mit Baumen
QUicksort: sortieren durch 2erlegen
S chi u s s b e m e rk u n 9 e n
Index
Jedes Verteuschen von zwei Arreyel ementen bewi rkt ei ne Veranderung
im Punktmuster. Somit konnen Sortierverfehren sichtber gemacht werden.
Figure 1. Commands to move through the sorting algorithms
r- -' .. Bewegungen S e it e n u e rz e i ch n is
. . .. ... . ."''''''J! '''-':J!J!'''-:-:J!-':'-''':«J!",!-:-:-:J!-:J!J!J!J!J!'':J!-:-:-C-:-:
Selectionsort: sortieren durch Auswahlen
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Figure 2. Screen of "selection sort"
20

Kontrolle Simul tion Darstellung Modelle Integration
.,
Stabi I i tat
Rauber-Beute Modell
R
1000
B
B = Beute t = Zeit
R =
Rauber
Figure 3. Simulation screen for prey-predator models
systems by means of differential and difference
equations. Much emphasis is placed on
simulations, to gain an intuitive insight into the
dynamic behaviour of nonlinear models, and to
complement the theoretical presentations in the
classroom. A screen used for the simulation of
prey-predator (Lotka-Volterra) systems is shown in
Fig. 3
The following set of programs has been especially
prepared for education in natural sciences:
Feedback Systems (Demo)
- Drosophila (Demo/Exercise)
- Euler Animation (Demo/Exercise)
- Probability (Demo)
- Stability (Demo/Exercise)
- Automaton (Demo/Exercise)
- Identification (Demo/Exercise)
- World Dynamics (Demo/Exercise)
For more details see Fischlin & Schaufelberger
(1987) or Fischlin, in Schaufelberger (1988a).
Control Engineering
Simulation is also an important aspect of a basic
education in control engineering used both for
classroom demonstrations and for individual
exercises by student. The relation between polelocations
and the dynamic behaviour of a system
can easily be studied by means of a corresponding
computer program. The set of programs that is in
use for this and related purposes consists of
- Tuning of two tenn controllers
- Anti-windup circuits
State variable feedback and observer design
Adaptive control
LIP identification
Rule based controller design (small expert
system shell)
Decision table analysis
Petri net simulation and reachability
A typical screen is shown in Fig. 4:
21

Kontrolle
Regier
.,
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2.00
1.00
0.00
steuergrosse u
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-
... --.-:."':.:'- - - "'--------
- 1.00 - 1.00
0.00 5.00 10.00 15.00
Zeit
0.00 5.00 10.00 15.00
Zeit
r PI-Regler Strecke
Imaginortei I
!L-
1 y
(s-a)(s-b)(s-c)
2.00 I- x
0.00 1---)(. )(
- Kp = 1.00 Ki = 0.00 -- Kp = 2.00 Ki
-._-
Kp = 2.00 Ki = 1.00
I
= 0.00
.
-2.50 0.00 2.50
Real tei I
x
Figure 4. Tuning of a two-term controller on a third-order plant
Details may be found in Schaufelberger (1988b),
and Schaufelberger (1988c).
Mathematical Tools
Tools differ from the special training programs
presented so far in that they can be tuned to and used
on many problems. The favorites in use in different
courses at ETH are Matlab, the public domain
version of the famous Matrix-Laboratory of Little
and Moler (1985), and ModelWorks, a simulation
environment based on MacMETH Modula-2 and
developed at ETH (Fischlin & Ulrich, 1987). A
solution of the Van der Pol equation is shown in Fig.
5:
Both Matlab and ModelWorks are available to all
students of ETH.
Authoring Systems
During the last two years, several authoring
systems have been developed at ETH. Since its
appearance, Hypercard is widely used. Most of the
programs presented here have been integrated into
Hypercard stacks, providing a new learning
environment for students and an innovative way of
composing course notes in a joint effort by faculty
and students.
The stack used for the computer science programs is
shown in Fig. 6:
The "DialogMachine", the basic authoring system
for simulations developed at the Project Center IDA
will be briefly presented. It consists of 14 Modula-2
Modules (16K LOC, 700 K Code) which allow the
easy programming of the Macintosh without ever
consulting "Inside Macintosh". Menus, windows,
input-output etc. are all available through a large set
of procedures. Inversed control structure
programming is used to simplify the author's task.
The Dialog Machine is so far in use at about 80
locations. The import/export relations of the
Modules are shown in Fig. 7:
22

Control SetUp Reset Windows Simulation
.,
Models
Monitorable uariables
Sj; _ ? Mode 1 names Monitor ab le v ariab le names
--+--:-+-+'--:
... ... Van der Pol Oscmaor
----==-++-=:_t
Van der Pol Oscillator
+---: x (abscissa)
y (ordinate)
x
y
Graph
1.0
0.8
0.5
I--+---i
t--+-P ....,ar
Par
Model Parameters
P ar ameer names
Van der Pol Oscillator
11 (oscillator parameter)
0.2
0.0
-4.0 -2.0
0.0 2.0
4.0
Plotted c:urves: Minimum Maximum
-y -5.000 5.000
x
State uariables
State variable names
""--""--1
Van der Pol Oscillator
""""-"....--1 x (xDo := y)
y (y Dot := Il( 1-x"'2)y -x)
x
y
Figure 5. Phase plane of the Van der Pol equation
r
.,
Sortierverfahren im Vergieich
Visualisierung verschiedenerJ grundlegender Sortierverfahren:
Ein Array samt Inhalt wird durch ein Punktmuster graphisch
dargestellt. Das Vertauschen von Arrayelementen aussert sich in
einer Anderung des Punktmusters. Somit kann der Ablauf eines
Sortierverfahrens am Bildschirm beobachtet werden.
(
Start
)
Figure 6. Hypercard stack integrationg several educational programs
23

DMMaster
- Main control
- User events
r-
I
....
..
DMMenus
I ,.
-
DM'w'indow 10
I
-
DM'w'indows
• Menu installation i4- • 'w'indow related +-- • 'Window
and usage input I output management
-
I
.I",
I
. . '" . ..
...
I
T
.
I
DMEntry Forms
• I nput via modal
L
dialogs
.. '"
..
.I", "t..
r-
DMEditFie lds
• Input via modeless
dialogs
L
1" T
.I
II. .I",
-
DMLanguage
• Language Se-
1ection
I-
I ..
DMA1erts
• Messages
r-
I
T
I
DMConversions r-
DMFi1es
• Number to string
• Sequential text
and vice versa
files
I
T
-
I
i
I
T
J
DMSystem
·Sy stemspecific
ob jects (public)
...
,
DMBase
·Low level (only
interna lly used)
-
I
I
T
Figure 7. Module structure of the DiaIogMachine
24

The Use of Apple Macintosh Computers In Teaching at ETH Zurich
Conclusions
The computer is a new mass medium allowing twoway
communications. As we have shown by our
examples, there are many different approaches to
using computers in education. It will take time until
the characteristics of this new medium are
completely understood. Experimentation and .
analysis of the possibilities are therefore important.
Our experience shows that computers will play an
importanf role in the education at Technical
Universities. In our opinion, the widely spread
availability of small and relatively inexpensive
computers will drastically change not only
university education, but also post-graduate
formation and life-long learning habits.
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26