COMP 202 Foundations of Programming

Instructor: Juan Camilo Gamboa Higuera

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Announcements

1. The first assignment is out

   Due on September 19th

2. Computer Science Undergraduate Society Help Desk

   Trottier 3rd floor.

   Monday & Tuesday & Wednesday & Thursday from 1:00pm - 5:00pm

   Starts on September 15th.

3. COMP 202 course requirement

   If you're in CS and you know programming, you can skip this and take COMP 250

   If you're not in CS, talk to your academic advisor

This week

1. Preliminary remarks

   Motivations

   Expectations

   Course Administration

2. Basic concepts

   Algorithms

   Binary

   ASCII

3. Basic tools for this course

   Scratch

   Java

   Eclipse

In the last class...

How is information represented on a computer?

Bit: 0 or 1

Counting with bits:

173

How is information represented on a computer?

Encoding text with binary

ASCII: American Standard Code for Information Interchange

Other encodings: UTF-8 (Unicode), ISO-8859-1

What is an algorithm?

A sequence of instructions that transforms some initial conditions into some desired final conditions

e.g.

• Arithmetic operations
• Sorting your groceries in alphabetical order
• Counting the number of people in a room

A sequence of instructions that transforms data

Two numbers into the result of an arithmetic operation

A yes/no question into an answer: yes or no (Decision)

A question about a set of numbers into a number that answers that question (Search)

The example from last's class video

Count the number of people in a room

Today's example

Find the maximum number in a given list of numbers

• Input : A list of numbers L. For example, {10,0,99,1,255,1,3,2}

• Output : A number in L that is bigger than any other number in L
• State : The value of the variables at any given time during execution
• Correctness : The expected output is obtained for any valid input

What is a programming language?

A way of translating algorithms into instructions executable by a computer

public class Example1 { public static void main(String[] args) { int[] L = {10,0,99,1,255,1,3,2}; int MAX= L[0]; for(int n: L){ if(n>MAX){ MAX=n; } } System.out.println(MAX); } }

Ugly syntax that is ultimately transformed into a machine code (i.e. binary), which is executable by a computer

A more gentle introduction

Scratch! (clicky)

A sneak peek into Java

Code! (clicky)

• Java files end in .java

• Java code gets transformed into machine code (bytecode)

  javac Example1.java

  This creates a file called Example1.class, containing the bytecode

• Java bytecode can be executed by you computer

  java Example1

Resources

• The Scratch website:
  scratch.mit.edu
• Download the Java Development Kit:
  http://www.oracle.com/technetwork/java/javase/downloads/jdk7-downloads-1880260.html
• Download the Eclipse IDE:
  https://www.eclipse.org/