Welcome to CSE 142 Brett Wortzman University of Washington Summer 2011 1 Who cares 2 1 Who cares 3 What is computer science computers science programming late lonely nights in front of the computer ALGORITHMIC THINKING al go rithm a step by step procedure for solving a problem or accomplishing some end especially by a computer Computer Engineering the E in CSE Overlap with CS and EE emphasizes hardware 4 2 Fields of computer science Graphics Computer Vision Artificial Intelligence Robotics Data Mining Natural Language Processing User Interfaces How does this all relate to programming This course is Introduction to Programming I after all 5 What is programming program A set of instructions to be carried out by a computer program execution The act of carrying out the instructions contained in a program programming language A systematic set of rules used to describe computations in a format that is understandable and editable by humans We will be studying a programming language called Java 6 3 Should you take this course No I hate computers I don t pay attention to details Programming is fairly detail oriented I refuse to think logically I want to take an easy class Hard for those who find difficulty in logical thinking and who don t pay attention to details 7 Should you take this course Probably not I want free gourmet meals and to make lots of money by working for Google World of Warcraft rocks hardcore Everyone look at my Facebook farm I ve programmed before so I can just coast through this for an easy A Yes I have to take this class Is this the only reason Are you pursuing the right major I like to solve problems Computers and robots are going to take over the world I want to befriend them so that my life will be spared 8 4 Should you take this course Absolutely I want to learn a fun interesting useful new skill I ll remember that it was stupid to be intimidated by programming I thought CSE was for supernerdy boys and that I just wouldn t be able to do it Now I think it s kind of fun Samantha C CSE 142 student Spring 2011 9 How to do well in this course Keep up with the assignments The course material is cumulative From a former student Procrastination will eventually come around to bite you in the ass Utilize all your resources Come to lecture go to section read the book go to the IPL post on the message board e mail your TA etc If you don t understand something ask questions especially WHY There s no such thing as a dumb question Computers are neither magical nor mysterious Everything can be explained 10 5 How to not do well in this course Violate the academic integrity policy From the syllabus Programming assignments must be completed individually all code you submit must be your own work You may discuss general ideas of how to approach an assignment but never specific details about the code to write If this policy is violated the helper and the helpee are both equally guilty Violating this policy carries consequences anywhere from a zero on the assignment to academic probation from the university 11 Building Java Programs Chapter 1 Lecture 1 1 Introduction Basic Java Programs reading 1 1 1 3 12 6 Programming languages Some influential ones FORTRAN science engineering COBOL business data LISP logic and AI BASIC a simple language 13 Some modern languages procedural languages programs are a series of commands Pascal 1970 designed for education C 1972 low level operating systems and device drivers functional programming functions map inputs to outputs Lisp 1958 Scheme 1975 ML 1973 Haskell 1990 object oriented languages programs use interacting objects Smalltalk 1980 first major object oriented language C 1985 object oriented improvements to C successful in industry used to build major OSes such as Windows Java 1995 designed for embedded systems web apps servers Runs on many platforms Windows Mac Linux cell phones The language taught in this textbook 14 7 Why Java Relatively simple Object oriented Pre written software Platform independent Widely used 1 in popularity ie http www tiobe com 15 Your first Java program public class Hello public static void main String args System out println Hello world File must be named Hello java What does this code output print to the user when you run execute it 16 8 Running a program 1 Write it code or source code The set of instructions in a program 2 Compile it compile Translate a program from one language to another byte code The Java compiler converts your code into a format named byte code that runs on many computer types 3 Run execute it output The messages printed to the user by a program source code output byte code compile run 17 Bigger Java program public class Hello public static void main String args System out println Hello world System out println System out println This program produces System out println four lines of output Its output Hello world This program produces four lines of output console Text box into which the program s output is printed 18 9 Structure of a Java program class a program public class name public static void main String args statement statement method a named group of statements statement statement a command to be executed Every executable Java program consists of a class that contains a method named main that contains the statements commands to be executed 19 System out println A statement that prints a line of output on the console pronounced print linn Two ways to use System out println System out println text Prints the given message as output System out println Prints a blank line of output 20 10 Syntax syntax The set of legal structures and commands that can be used in a particular language The spelling and grammar of a programming language Every basic Java statement ends with a semicolon The contents of a class or method occur between and syntax error compiler error A problem in the structure of a program that causes the compiler to fail Missing semicolon Too many or too few braces Class and file names do not match 21 Syntax error example 1 2 3 4 5 public class Hello pooblic static void main String args System owt println Hello world Compiler output Hello java 2 identifier expected pooblic static void main String args Hello java 3 expected 2 errors The compiler shows the line number where it found the error The error messages sometimes can be tough to understand Why can t the computer just say You misspelled public 22 11 First lesson in this class Computers are stupid Computers can t read minds
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