Chapter 1 Introduction PDF

Chapter 1 Introduction Java Software Solutions Foundations of Program Design Seventh Edition John Lewis William Loftus Copyright © 2012 Pearson Education, Inc. Focus of the Course Object-Oriented Software Development – prob...

Chapter 1 Introduction Java Software Solutions Foundations of Program Design Seventh Edition John Lewis William Loftus Copyright © 2012 Pearson Education, Inc. Focus of the Course Object-Oriented Software Development – problem solving – program design, implementation, and testing – object-oriented concepts classes objects encapsulation inheritance polymorphism – graphical user interfaces – the Java programming language Copyright © 2012 Pearson Education, Inc. Introduction We start with the fundamentals of computer processing Chapter 1 focuses on: – components of a computer – how computers store and manipulate information – computer networks – the Internet and the World Wide Web – programming and programming languages – an introduction to Java – an overview of object-oriented concepts Copyright © 2012 Pearson Education, Inc. Outline Computer Processing Hardware Components Networks The Java Programming Language Program Development Object-Oriented Programming Copyright © 2012 Pearson Education, Inc. Hardware and Software Hardware – the physical, tangible parts of a computer – keyboard, monitor, disks, wires, chips, etc. Software – programs and data – a program is a series of instructions A computer requires both hardware and software Each is essentially useless without the other Copyright © 2012 Pearson Education, Inc. CPU and Main Memory Central Chip that Processing executes Unit program commands Primary storage area for programs and data that are Main in active use Memory Synonymous with RAM Copyright © 2012 Pearson Education, Inc. Input / Output Devices Monitor screen Central Keyboard Processing Mouse Unit Touch screen I/O devices facilitate user interaction Main Memory Copyright © 2012 Pearson Education, Inc. Secondary Memory Devices Information is moved Central between main and Processing secondary memory Unit as needed Hard Disk Secondary memory Main devices provide Memory long-term storage USB Flash Drive Copyright © 2012 Pearson Education, Inc. Software Categories Operating System – controls all machine activities – provides the user interface to the computer – manages resources such as the CPU and memory – Windows, Mac OS, Unix, Linux, Application program – generic term for any other kind of software – word processors, missile control systems, games Most operating systems and application programs have a graphical user interface (GUI) Copyright © 2012 Pearson Education, Inc. Analog vs. Digital There are two basic ways to store and manage data: Analog – continuous, in direct proportion to the data represented – music on a record album - a needle rides on ridges in the grooves that are directly proportional to the voltages sent to the speaker Digital – the information is broken down into pieces, and each piece is represented separately – sampling – record discrete values of the analog representation – music on a compact disc - the disc stores numbers representing specific voltage levels sampled at specific times Copyright © 2012 Pearson Education, Inc. Analog Information Copyright © 2012 Pearson Education, Inc. Sampling Copyright © 2012 Pearson Education, Inc. Digital Information Computers store all information digitally: – numbers – text – graphics and images – audio – video – program instructions In some way, all information is digitized - broken down into pieces and represented as numbers Copyright © 2012 Pearson Education, Inc. Representing Text Digitally For example, every character is stored as a number, including spaces, digits, and punctuation Corresponding upper and lower case letters are separate characters Hi, Heather. 72 105 44 32 72 101 97 116 104 101 114 46 Copyright © 2012 Pearson Education, Inc. Binary Numbers Once information has been digitized, it is represented and stored in memory using the binary number system A single binary digit (0 or 1) is called a bit Devices that store and move information are cheaper and more reliable if they have to represent only two states A single bit can represent two possible states, like a light bulb that is either on (1) or off (0) Permutations of bits are used to store values Copyright © 2012 Pearson Education, Inc.  Bit Permutations 1 bit 2 bits 3 bits 4 bits 0 00 000 0000 1000 1 01 001 0001 1001 10 010 0010 1010 11 011 0011 1011 100 0100 1100 101 0101 1101 110 0110 1110 111 0111 1111 Each additional bit doubles the number of possible permutation Copyright © 2012 Pearson Education, Inc. Bit Permutations Each permutation can represent a particular item There are 2N permutations of N bits Therefore, N bits are needed to represent 2 N unique items 1 bit ? 21 = 2 items How many 2 bits ? 22 = 4 items items can be 3 bits ? 23 = 8 items represented by 4 bits ? 24 = 16 items 5 bits ? 25 = 32 items Copyright © 2012 Pearson Education, Inc. Quick Check How many bits would you need to represent each of the 50 United States using a unique permutation of bits? Copyright © 2012 Pearson Education, Inc. Quick Check How many bits would you need to represent each of the 50 United States using a unique permutation of bits? 000000 Alabama Five bits wouldn't be 000001 Alaska enough, because 25 is 32. 000010 Arizona 000011 Arkansas Six bits would give us 64 000100 California permutations, and some 000101 Colorado wouldn't be used. etc. Copyright © 2012 Pearson Education, Inc. Outline Computer Processing Hardware Components Networks The Java Programming Language Program Development Object-Oriented Programming Copyright © 2012 Pearson Education, Inc. A Computer Specification Consider the following specification for a personal computer: – 3.07 GHz Intel Core i7 processor – 4 GB RAM – 750 GB Hard Disk – 16x Blu-ray / HD DVD-ROM & 16x DVD+R DVD Burner – 17” Flat Screen Video Display with 1280 x 1024 resolution – Network Card Copyright © 2012 Pearson Education, Inc. Computer Architecture Copyright © 2012 Pearson Education, Inc. Memory 9278 Main memory is 9279 divided into many 9280 memory locations 9281 (or cells) 9282 9283 Each memory cell 9284 has a numeric 9285 address, which 9286 uniquely identifies it Copyright © 2012 Pearson Education, Inc. Storing Information 9278 Each memory cell 9279 10011010 stores a set number of bits (usually 8 9280 bits, or one byte) 9281 Large values are 9282 stored in consecutive 9283 memory locations 9284 9285 9286 Copyright © 2012 Pearson Education, Inc. Storage Capacity Every memory device has a storage capacity, indicating the number of bytes it can hold Capacities are expressed in various units: Unit Symbol Number of Bytes kilobyte KB 210 = 1024 megabyte MB 220 (over one million) gigabyte GB 230 (over one billion) terabyte TB 240 (over one trillion) petabyte PB 250 (a whole bunch) Copyright © 2012 Pearson Education, Inc. Memory Main memory is volatile - stored information is lost if the electric power is removed Secondary memory devices are nonvolatile Main memory and disks are direct access devices - information can be reached directly The terms direct access and random access often are used interchangeably A magnetic tape is a sequential access device since its data is arranged in a linear order - you must get by the intervening data in order to access other information Copyright © 2012 Pearson Education, Inc. Hard Disk Drive Copyright © 2012 Pearson Education, Inc. RAM vs. ROM RAM - Random Access Memory (direct access) ROM - Read-Only Memory The terms RAM and main memory are basically interchangeable ROM could be a set of memory chips, or a separate device, such as a CD ROM Both RAM and ROM are random (direct) access devices! RAM probably should be called Read-Write Memory Copyright © 2012 Pearson Education, Inc. Compact Discs A CD-ROM is portable read-only memory A microscopic pit on a CD represents a binary 1 and a smooth area represents a binary 0 A low-intensity laser reflects strongly from a smooth area and weakly from a pit A CD-Recordable (CD-R) drive can be used to write information to a CD once A CD-Rewritable (CD-RW) can be erased and reused The speed of a CD drive indicates how fast (max) it can read and write information to a CD Copyright © 2012 Pearson Education, Inc. DVDs A DVD is the same physical size as a CD, but can store much more information The format of a DVD stores more bits per square inch A CD can store 650 MB, while a standard DVD can store 4.7 GB – A double sided DVD can store 9.4 GB – Other advanced techniques can bring the capacity up to 17.0 GB Like CDs, there are DVD-R and DVD-RW discs Copyright © 2012 Pearson Education, Inc. The Central Processing Unit A CPU is on a chip called a microprocessor It continuously follows the fetch-decode-execute cycle: Retrieve an instruction from main memory fetch execute decode Carry out the Determine what the instruction instruction is Copyright © 2012 Pearson Education, Inc. The Central Processing Unit Performs Arithmetic / Logic Unit calculations and makes decisions Coordinates Control Unit processing steps Small Registers storage areas Copyright © 2012 Pearson Education, Inc. The Central Processing Unit The speed of a CPU is controlled by the system clock The system clock generates an electronic pulse at regular intervals The pulses coordinate the activities of the CPU The speed is usually measured in gigahertz (GHz) Copyright © 2012 Pearson Education, Inc. Monitor The size of a monitor (17") is measured diagonally, like a television screen A monitor has a certain maximum resolution , indicating the number of picture elements, called pixels, that it can display (such as 1280 by 1024) High resolution (more pixels) produces sharper pictures Copyright © 2012 Pearson Education, Inc. Outline Computer Processing Hardware Components Networks The Java Programming Language Program Development Object-Oriented Programming Copyright © 2012 Pearson Education, Inc. Networks A network is two or more computers that are connected so that data and resources can be shared Most computers are connected to some kind of network Each computer has its own network address, which uniquely identifies it among the others A file server is a network computer dedicated to storing programs and data that are shared among network users Copyright © 2012 Pearson Education, Inc. Network Connections Each computer in a network could be directly connected to every other computer in the network These are called point-to-point connections Adding a computer requires a new communication line for each computer already in the network This technique is not practical for more than a few close machines Copyright © 2012 Pearson Education, Inc.  Network Connections Most networks share a single communication line Adding a new computer to the network is relatively easy Often information is broken Network traffic must take down in parts, called packets turns using the line, which introduces delays which are sent to the receivin machine and then reassemble Copyright © 2012 Pearson Education, Inc. A Computer Network Copyright © 2012 Pearson Education, Inc. Local-Area Networks A Local-Area Network (LAN) covers a small distance and a small number of computers LAN A LAN often connects the machine in a single room or building Copyright © 2012 Pearson Education, Inc.  Wide-Area Networks A Wide-Area Network (WAN) connects two or more LANs, often over long distances LAN LAN Copyright © 2012 Pearson Education, Inc. The Internet The Internet is a WAN which spans the planet The word Internet comes from the term internetworking It started as a United States government project, sponsored by the Advanced Research Projects Agency (ARPA) – originally it was called the ARPANET The Internet grew quickly throughout the 1980s and 90s Copyright © 2012 Pearson Education, Inc. TCP/IP A protocol is a set of rules that determine how things communicate with each other The software that manages Internet communication follows a suite of protocols called TCP/IP The Internet Protocol (IP) determines the format of the information as it is transferred The Transmission Control Protocol (TCP) dictates how messages are reassembled and handles lost information Copyright © 2012 Pearson Education, Inc. IP and Internet Addresses Each computer on the Internet has a unique IP address, such as: 204.192.116.2 Most computers also have a unique Internet name, which also is referred to as an Internet address: hector.vt.edu kant.gestalt-llc.com The first part indicates a particular computer (hector) The rest is the domain name, indicating the organization (vt.edu) Copyright © 2012 Pearson Education, Inc. Domain Names The last part of a domain name, called a top-level domain (TLD), supposedly indicates the type of organization: edu educational institution com commercial entity org non-profit organization net network-based organization Sometimes the suffix indicates the country: Additional TLDs have been added: uk United Kingdom au Australia biz, info, tv, name ca Canada se Sweden Copyright © 2012 Pearson Education, Inc. Domain Names A domain name can have several parts Unique domain names mean that multiple sites can have individual computers with the same local name When used, an Internet address is translated to an IP address by software called the Domain Name System (DNS) There is no one-to-one correspondence between the sections of an IP address and the sections of an Internet address Copyright © 2012 Pearson Education, Inc. The World Wide Web The World Wide Web allows many different types of information to be accessed using a common interface A browser is a program which accesses network resources and presents them – Popular browsers: Internet Explorer, Safari, Firefox Resources presented include: – text, graphics, video, sound, audio, executable programs A Web document usually contains links to other Web documents, creating a hypermedia environment The term Web comes from the fact that information is not organized in a linear fashion Copyright © 2012 Pearson Education, Inc. The World Wide Web Web documents are often defined using the HyperText Markup Language (HTML) Information on the Web is found using a Uniform Resource Locator (URL): http://www.cnn.com http://www.vt.edu/student_life/index.html ftp://java.sun.com/applets/animation.zip A URL specifies a protocol (http), a domain, and possibly specific documents Copyright © 2012 Pearson Education, Inc. Outline Computer Processing Hardware Components Networks The Java Programming Language Program Development Object-Oriented Programming Copyright © 2012 Pearson Education, Inc. Java The Java programming language was created by Sun Microsystems, Inc. It was introduced in 1995 and it's popularity has grown quickly since A programming language specifies the words and symbols that we can use to write a program A programming language employs a set of rules that dictate how the words and symbols can be put together to form valid program statements Copyright © 2012 Pearson Education, Inc. Java Program Structure In the Java programming language: – A program is made up of one or more classes – A class contains one or more methods – A method contains program statements These terms will be explored in detail throughout the course A Java application always contains a method called main See Lincoln.java Copyright © 2012 Pearson Education, Inc. / Copyright © 2012 Pearson Education, Inc. Identifiers Identifiers are the "words" in a program A Java identifier can be made up of letters, digits, the underscore character ( _ ), and the dollar sign Identifiers cannot begin with a digit Java is case sensitive: Total, total, and TOTAL are different identifiers By convention, programmers use different case styles for different types of identifiers, such as – title case for class names - Lincoln – upper case for constants - MAXIMUM Copyright © 2012 Pearson Education, Inc. Identifiers Sometimes the programmer chooses the identifer(such as Lincoln) Sometimes we are using another programmer's code, so we use the identifiers that he or she chose (such as println) Often we use special identifiers called reserved words that already have a predefined meaning in the language A reserved word cannot be used in any other way Copyright © 2012 Pearson Education, Inc. Reserved Words The Java reserved words: abstract else interface switch assert enum long synchronized boolean extends native this break false new throw byte final null throws case finally package transient catch float private true char for protected try class goto public void const if return volatile continue implements short while default import static do instanceof strictfp double int super Copyright © 2012 Pearson Education, Inc. Quick Check Which of the following are valid Java identifiers? grade quizGrade NetworkConnection frame2 3rdTestScore MAXIMUM MIN_CAPACITY student# Shelves1&2 Copyright © 2012 Pearson Education, Inc. Quick Check Which of the following are valid Java identifiers? grade Valid quizGrade Valid NetworkConnection Valid frame2 Valid 3rdTestScore Invalid – cannot begin with a digit MAXIMUM Valid MIN_CAPACITY Valid student# Invalid – cannot contain the '#' character Shelves1&2 Invalid – cannot contain the '&' character Copyright © 2012 Pearson Education, Inc. White Space Spaces, blank lines, and tabs are called white space White space is used to separate words and symbols in a program Extra white space is ignored A valid Java program can be formatted many ways Programs should be formatted to enhance readability, using consistent indentation See Lincoln2.java and Lincoln3.java Copyright © 2012 Pearson Education, Inc. Outline Computer Processing Hardware Components Networks The Java Programming Language Program Development Object-Oriented Programming Copyright © 2012 Pearson Education, Inc. Program Development The mechanics of developing a program include several activities: – writing the program in a specific programming language (such as Java) – translating the program into a form that the computer can execute – investigating and fixing various types of errors that can occur Software tools can be used to help with all parts of this process Copyright © 2012 Pearson Education, Inc. Language Levels There are four programming language levels: – machine language – assembly language – high-level language – fourth-generation language Each type of CPU has its own specific machine language The other levels were created to make it easier for a human being to read and write programs Copyright © 2012 Pearson Education, Inc. Programming Languages Each type of CPU executes only a particular machine language A program must be translated into machine language before it can be executed A compiler is a software tool which translates source code into a specific target language Often, that target language is the machine language for a particular CPU type The Java approach is somewhat different Copyright © 2012 Pearson Education, Inc. Java Translation The Java compiler translates Java source code into a special representation called bytecode Java bytecode is not the machine language for any traditional CPU Another software tool, called an interpreter, translates bytecode into machine language and executes it Therefore the Java compiler is not tied to any particular machine Java is considered to be architecture-neutral Copyright © 2012 Pearson Education, Inc. Java Translation Java source code Java bytecode Java compiler Bytecode Bytecode interpreter compiler Machine code Copyright © 2012 Pearson Education, Inc. Development Environments There are many programs that support the development of Java software, including: – Java Development Kit (JDK) – Eclipse – NetBeans – BlueJ – jGRASP Though the details of these environments differ, the basic compilation and execution process is essentially the same Copyright © 2012 Pearson Education, Inc. Syntax and Semantics The syntax rules of a language define how we can put together symbols, reserved words, and identifiers to make a valid program The semantics of a program statement define what that statement means (its purpose or role in a program) A program that is syntactically correct is not necessarily logically (semantically) correct A program will always do what we tell it to do, not what we meant to tell it to do Copyright © 2012 Pearson Education, Inc. Errors A program can have three types of errors The compiler will find syntax errors and other basic problems (compile-time errors) – If compile-time errors exist, an executable version of the program is not created A problem can occur during program execution, such as trying to divide by zero, which causes a program to terminate abnormally (run-time errors) A program may run, but produce incorrect results, perhaps using an incorrect formula (logical errors) Copyright © 2012 Pearson Education, Inc. Basic Program Development Edit and save program errors? errors? Compile program Execute program and evaluate results Copyright © 2012 Pearson Education, Inc. Outline Computer Processing Hardware Components Networks The Java Programming Language Program Development Object-Oriented Programming Copyright © 2012 Pearson Education, Inc. Problem Solving The purpose of writing a program is to solve a problem Solving a problem consists of multiple activities: – Understand the problem – Design a solution – Consider alternatives and refine the solution – Implement the solution – Test the solution These activities are not purely linear – they overlap and interact Copyright © 2012 Pearson Education, Inc. Problem Solving The key to designing a solution is breaking it down into manageable pieces When writing software, we design separate pieces that are responsible for certain parts of the solution An object-oriented approach lends itself to this kind of solution decomposition We will dissect our solutions into pieces called objects and classes Copyright © 2012 Pearson Education, Inc. Object-Oriented Programming Java is an object-oriented programming language As the term implies, an object is a fundamental entity in a Java program Objects can be used effectively to represent real- world entities For instance, an object might represent a particular employee in a company Each employee object handles the processing and data management related to that employee Copyright © 2012 Pearson Education, Inc. Objects An object has: – state - descriptive characteristics – behaviors - what it can do (or what can be done to it) The state of a bank account includes its account number and its current balance The behaviors associated with a bank account include the ability to make deposits and withdrawals Note that the behavior of an object might change its state Copyright © 2012 Pearson Education, Inc. Classes An object is defined by a class A class is the blueprint of an object The class uses methods to define the behaviors of the object The class that contains the main method of a Java program represents the entire program A class represents a concept, and an object represents the embodiment of that concept Multiple objects can be created from the same class Copyright © 2012 Pearson Education, Inc. Class = Blueprint One blueprint to create several similar, but different, houses: Copyright © 2012 Pearson Education, Inc. Objects and Classes An object A class (the realization) (the concept) John’s Bank Account Bank Balance: $5,257 Account Bill’s Bank Account Balance: $1,245,069 Multiple objects from the same class Mary’s Bank Account Balance: $16,833 Copyright © 2012 Pearson Education, Inc. Inheritance One class can be used to derive another via inheritance Classes can be organized into hierarchies Account Charge Bank Account Account Savings Checking Account Account Copyright © 2012 Pearson Education, Inc. Summary Chapter 1 focused on: – components of a computer – how those components interact – how computers store and manipulate information – computer networks – the Internet and the World Wide Web – programming and programming languages – an introduction to Java – an overview of object-oriented concepts Copyright © 2012 Pearson Education, Inc.