Welcome to CS120 Fall 2012

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1 Welcome to CS120 Fall 2012 John Magee 1 Welcome to CS120 Computing is ubiquitous Daily life, news, ecommerce Sciences and engineering fields Social sciences, humanity, Arts, music, sports Education 1

Computing One core objective of computing is efficient problem solving Computing shares common methodologies with other fields Given a problem, how to Understand it, formulate it, make hypotheses

2 Computing One core objective of computing is efficient problem solving Computing shares common methodologies with other fields Given a problem, how to Understand it, formulate it, make hypotheses Many computing problems come from other fields Design a solution strategies for big problems, such as divide and conquer Implement a solution Should be done in a systematic, disciplined fashion Test a solution Revise, improve CS120 Object-oriented programming Graphics/animation-based problems Alice: A 3D animation language Java: an Eventful Approach Main topics Methods Variables and functions Control structures Lists and Arrays Events Classes 2

3 Why Learn Programming? Programming is a challenging and intellectually engaging experience. Programming is a part of computer science, and is therefore important to anyone interested in becoming a computer professional. 5 Why Learn Programming? Computers have become commonplace in our society, and understanding their strengths and limitations requires an understanding of programming. Programming can be a lot of fun. Programming is a skill that can pay the bills. Very well. 6 3

4 About Learning to Program Pre-requisites This is a first course in computer science. There are no formal pre-requisites. Some informal pre-req s: using , browsing the web copying and pasting text some high-school level algebra Time Anyone can be successful at learning programming. Decent results, however, take a lot of time. 7 How do we get there? Lectures Teaching Labs Weekly Homeworks Projects Midterm Written Exam and Practical Exam 8 9 4

5 Expectations Attendance This is not a correspondence course. Participation Questions and discussion are what makes the class interesting. 9 9 Administrative Questions?

6 What You ll Learn Today What is computer science? What is a computer? What are hardware and software? How can computers learn new tricks? What is Programming? 11 What is Computer Science? 12 6

7 What is CS? The fundamental ideas of CS are: Algorithms Protocols Encoding Information Abstraction 13 Flashlight Messaging Imagine you are 10 years old, in Your best friend lives next door. You want to send messages at night. You each have a flashlight. What do you do? 14 7

8 ABC means (Meet me at Starbucks) 15 Numbered Code Replace each character with a number Coded Message Example: Encoding is about converting data into a coded form. Decoding is about converting from coded to normal form. 16 8

9 Algorithm An algorithm is a sequence of clear and precise step-by-step instructions for solving a problem in a finite amount of time. 17 Protocols A protocol is a set of rules governing the exchange or transmission of data between devices. 18 9

10 The Braille Encoding Scheme Each character is up to 6 dots. Each dot is either on or off. Invented by Louis Braille ( ). 19 What are we looking at? 20 10

11 No, this is the matrix! 21 What is this? 22 11

23 Abstraction Abstraction is about hiding unnecessary

12 Your web browser interprets the coded data (1s and 0s) and renders the Facebook webpage. 23 Abstraction Abstraction is about hiding unnecessary details and retaining only the relevant information. Eg. Tie your shoe Drive a car 24 12

13 Encoding/Decoding The binary coded data (1s and 0s) is what your web browser interprets as the Facebook webpage. How? The digital computer is a machine which encodes, processes, and decodes data. 25 Data and Information Data is a fact pattern: Information is how we interpret that pattern: 26 13

14 What is a Computer? What is a computer, anyway? A computer takes an input, applies a process, and produces an output. Give some examples: 27 2 What is a Computer? 28 14

15 Hardware 29 3 Software

16 Early History of Computing Joseph Jacquard (1801) Jacquard s Loom, the punched card 31 Harvard Mark I IBM Archives 32 16

First Computer Bug Log of first computer bug, discovered by Grace Hopper, 1945 A Computer Science Pioneer, she later wrote the first Compiler. 33 Programmability What tricks does your computer do?

17 First Computer Bug Log of first computer bug, discovered by Grace Hopper, 1945 A Computer Science Pioneer, she later wrote the first Compiler. 33 Programmability What tricks does your computer do? Web browsing, , instant messenger Play games Watch movies, organize photos Word processing, spreadsheets, database Programmability is the ability to give a generalpurpose computer instructions so that it can perform new tasks

18 Programming Languages A program is a sequence of instructions. Spock: Computer. This is a Class-A compulsory directive. Compute, to the last digit, the value of pi. Computers are not very good at understanding natural languages Ambiguity and imprecision Dialects, accents, etc 35 Programming Languages Computer languages are exact and unambiguous. Programming is the process of encoding our ideas for the computer: Syntax (form) Semantics (meaning) Popular programming languages: BASIC, C++, Java, Perl, Python 36 18

19 Machine Language Computing hardware performs only a small set of concrete operations, which are created in circuitry: load the number from memory location 2001 into the CPU load the number from memory location 2002 into the CPU add the two numbers in the CPU store the result into location 2003 These instructions must be provided to the CPU as binary notation (1s and 0s), called machine language 37 High Level Languages Java is a high-level language c = a + b High level languages are more natural for us to understand, but need to be translated into the machine language for execution

20 Alice A modern programming tool 3-D graphics 3-D models of objects Animation Objects can be made to move around the virtual world (a video game or simulation implemented in 3-D) Two kinds of animations: Movie: passive user watches the animation Interactive: active user clicks on mouse, types a key on keyboard Actions of user are called events Getting and Running Alice Alice software is freely distributed Downloading Alice Go to the website: Click the link Get Alice 2.2 Click download link specific to your operating system Save Alice.zip (or Alice.dmg) to your PC Installing and running Alice Extract Alice from Alice.zip (or Alice.dmg) file Create desktop shortcut (alias) to Alice.exe Double-click Alice icon to launch Alice application 41 20

The Alice Tutorials (continued) Go through the tutorials to learn the basics of Alice 42 Alice Drag-and-drop based programming Major advantage: preventing syntax errors Limitations Restricted editing

21 The Alice Tutorials (continued) Go through the tutorials to learn the basics of Alice 42 Alice Drag-and-drop based programming Major advantage: preventing syntax errors Limitations Restricted editing Restricted reusing Statement resusable within a method (but not statements) Clipboards available for copying and pasting statements between methods of a class (but not all statements) Saving a object (with newly defined methods) as a class for using in other worlds Objects need to be pre-created (inconv. for arrays) 21

22 User Stories Contain Basic description of what happens when program runs Nouns in story (Alice, the White Rabbit) correspond to objects Verbs correspond to actions, responses to messages Chronological flow describes the sequence of the actions When the program begins, Alice and the White Rabbit are facing each other, Alice on the left and the White Rabbit on the right. Alice turns her head and then greets us. The White Rabbit also turns and then greets us. Alice and the White Rabbit introduce themselves. Simultaneously, Alice and the White Rabbit say Welcome to our world. Alice in Action with Java 44 User Story and Story Board A numbered sequence of objects and actions 1. Alice turns her head toward the user 2. Alice greets the user 3. The white rabbit turns toward the user 4. The white rabbit greets the user 5. Alice introduces herself 6. The white rabbit introduces himself 7. Simultaneously, Alice and the white rabbit say Welcome to our world. Alice in Action with Java 45 22

23 Program Design For a given user story plan scents and shots Scene: a piece of the story usually set in one location Shot: part of scene told with camera in one position Create storyboards Alice in Action with Java 46 Topics in CS120 Eventful Java (tentative) Events Primitive types Control Structures Classes Arrays (Animation?) 23

24 What You Learned Today Computer Science is A Computer is Hardware vs. Software Programmability Programming Languages Machine language vs. high level Introducing Alice and Java 48 Announcements and To Do List Visit the course web page Download Alice 2.2 Do the tutorials Readings: Alice in Action, Chapter

CSCI170 Lecture 1: Analysis of Programming Languages. John Magee 1 September 2011 Some material copyright Jones and Bartlett

CSCI170 Lecture 1: Analysis of Programming Languages John Magee 1 September 2011 Some material copyright Jones and Bartlett 1 Overview/Questions How can we control the computer s circuits? How does the