Transcript Introduction to Computer Science I

Technische Universität Darmstadt
Telecooperation/RBG
Introduction to Computer Science I
Topic 0: Introduction
Prof. Dr. Max Mühlhäuser
Dr. Guido Rößling
Copyrighted material; for TUD student use only
Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
What Computer Science is Not About
The computer!
Just as biology is not “microscope science” and
writing is not “pen science”
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
The subject of ICS 1
Problem
Description
mental Model
Challenge: Formulating a
solution that is both easy to
understand for a human and
executable for a machine
huge
representational
gap
executable
program
machine layer
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
The role of ICS-1
– Introduction to Programming • Content constraints
• Sociological constraints
• Time constraints
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
The role of ICS-1
Parents: “CNN
talks a lot about Java.
Why do you teach
my child Scheme?”
Student: “I know
everything
and Perl is the best!”
ICS-1 Introduction
to Programming
Other Profs:
“Everybody in my
world needs
pointers. This is what
you should teach
in ICS-1!”
Industry: “Today
we are using
C# v4.538. Why don’t
you teach it to
your students?”
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
The role of ICS-1
Students who can program
on a similar level
ICS-1
Students with
mathematical
background
Students who
“program”
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Students without
previous knowledge
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
In many ICS-1 Courses…
• Classic ICS-1 course:
–
–
–
–
You learn the syntax of a fashionable programming language
You use a commercial development environment
You are shown code examples and asked to imitate them
You discuss a couple of algorithmic ideas
• The meaning of the language remains unclear
– superficial explanations
– explanation in terms of implementation details/ hardware
• How you can design new programs remains unclear
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
Tinkering vs. Design
• Syntax: Tinkering until it works
• Design: Tinkering until it works
• You know some standard algorithms, but this is no
replacement for a program design methodology
• Your knowledge about the meaning of the
language is a mixture of gut feeling and some
details about low-level implementation details of
the language
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
Work Environment of a Pilot
Appropriate for the first flying lesson?
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
Work Environment for Experienced Programmers
Appropriate for the first programs?
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
Our approach: 4 pillars
1. Development environment for beginners
2. Simple programming language
3. Precise models to understand the meaning
of the language
4. Recipes and methodology how to design programs
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
Development environment for beginners
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
Simple programming language
• You will not learn only one - but many different layered
programming languages
– Different levels, structured from the pedagogical point of view
• Subsets of the programming language Scheme
– Features that you don’t know yet are disabled
– No bizarre error messages regarding features you don’t know
• We can always concentrate on the design concepts and
ideas that fit your current standard of knowledge!
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
Precise Models to understand the
meaning of the language
For every language level, we will teach you a model which
explains the meaning of the various programs
– You can “execute” programs on a piece of paper
– These models are not defined in terms of hardware, but their
purpose is to specify the meaning in the simplest possible way
– You will also hear about models illustrating how a programming
language is implemented on typical hardware
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Recipes and methodology
“how to design programs”
Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
• We will not just present programs and ask you to imitate
• We teach recipes – that is, step-by-step instructions –
how you can design programs
– These recipes are more or less independent of the programming
language
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
Typical program “design” approach…
That is not how we will do it, though … 
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
From Scheme to Java
• In the second half of the semester we will use Java
• The design recipes work step-by-step also for objectoriented Java programs
• Many differences are just notation
• More fundamental differences are very instructive
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
Why not Java first?
• Complex notation, complex errors
• No IDE (integrated development environment) supports language
levels
• Direct interaction with Scheme interpreter makes it easier to get
started
• Design recipes are drown in syntax
– K.I.S.S. - Keep It Simple Syntactically
• Java/C++/Pascal: 90% syntax, 10% problem solving
• Scheme: 10% syntax, 90% problem solving
• Scheme (or Lisp) is the “mother” of most modern language features
– Language features can be studied in full “purity” in Scheme
– Many “new” features of modern languages can easily be understood
once you know Scheme
• Studies show that our approach produces better OO programmers!
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
Advantages of an easy language
We want to compute the sum of 2 and 3
DrScheme:
We enter the program (+ 2 3),
DrScheme responds “5”
The steps required in Java/Eclipse
are not “nonsense”, but all have
their meaning.
For a beginner, they can be confusing
and unnecessary.
Java/Eclipse:
We start a new project
We create a new package
We create a new class
We write the following program:
package test;
public class Test {
public static void main(String args[])
{
System.out.println(2+3);
}
}
(You need weeks before you understand
every part of this program)
We compile the program
We run the program
The console shows “5”
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
Summary
• Training good programmers does not mean starting them
on “currently fashionable” or professional tools &
languages
• We provide a strong, rigorous foundation in basic concepts
of programming
• Then, and only then, we will expose you to current
fashion!
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Books
Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
• Scheme:
– most important book:
How to Design
Programs (HTDP)
– Structure and Interpretations of
Computer Programs (SICP)
• Java
– Thinking in Java
all books available for free online!
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Dr. G. Rößling
Prof. Dr. M. Mühlhäuser
RBG / Telekooperation
©
More information
• News, Links, Lecture Notes etc. are all available on
our homepages:
http://proffs.tk.informatik.tu-darmstadt.de/gdi1
http://proffs.tk.informatik.tu-darmstadt.de/gdi1/en
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