The University of Akron Summit College

1. The University of AkronSummit College 2440: 160Java Programming Introduction to Computers & Java Professor: Enoch E. Damson

2. Parts of an Information System • Hardware • Software • Procedures • Data • People Introduction to Computers & Java

3. Hardware • Physical components of a computer • Consists of: • Input devices • Processor or Central Processing Unit (CPU) • Main memory • Secondary storage devices • Output devices Introduction to Computers & Java

4. Input Devices • Collects data for the computer • Common devices include: • Keyboard • Mouse • Scanner • Digital camera Introduction to Computers & Java

5. Central Processing Unit (CPU) • Fetches instructions, follow the instructions, and produce some resulting data • Measured in terms of its speed in hertz (MHz, GHz) • Consists of two parts: • Control Unit – coordinates all of the computer’s operations • Arithmetic & Logic Unit (ALU) – performs mathematical operations Introduction to Computers & Java

6. Main Memory • Commonly known as the random-access memory (RAM) • Measured in terms of its size in bytes (KB, MB, GB) • RAM is usually a volatile type of memory for temporary storage • Divided into sections (bytes) that hold equal amount of data • Each byte is made up of 8binary digits (bits) that use 0 and 1 to represents on and off “switches” • Each byte is a assigned a unique number known as an address, which are ordered from lowest to highest Introduction to Computers & Java

7. Secondary Storage Devices • Type of memory that hold data for long periods of time • Measured in terms of their size in bytes (KB, MB, GB) • Common types of secondary storage devices include: • Hard disks • Jump drives • Zip disks • Floppy disks Introduction to Computers & Java

8. Output Devices • Formats and presents processed data (information) to the outside world • Common devices include: • Monitors • Printers Introduction to Computers & Java

9. Software • Programs that run on a computer • Has two general categories: • System software – enables application software to interact with the computer hardware • E.g. operating systems, utilities, device drivers, and programming languages • Application software – programs that solve specific problems or perform general operations useful to the user • E.g. word processors, spreadsheets, etc Introduction to Computers & Java

10. Procedures • Rules or guidelines for people to follow when using software, hardware, and data • Guidelines are documented in manuals Introduction to Computers & Java

11. Data • Raw facts entered into the computer system for processing • Processed to produce information Introduction to Computers & Java

12. People • Making people more productive is what computers are all about • Users include: • Analysts • Designers • Developers • End-users Introduction to Computers & Java

13. Computer Program • Set of instructions that enables the computer to solve a problem or perform a task • The instructions are called algorithms • A computer’s CPU can only process algorithms written in machine language – consisting of binary numbers (0s and 1s) • E.g. 1011010000000101 • Each different type of CPU has its own machine language • Algorithms written with programming languages are much easier to understand Introduction to Computers & Java

14. Computer Programming • An art and a science of creating instructions to solve problems and perform tasks • An art because every aspect of the program should be carefully designed • A science because of the need to indulge in the tasks of analyzing, experimenting, correcting, and redesigning Introduction to Computers & Java

15. Program Development (Programming) Cycle • The process of writing instructions (programs) for a computer to solve a problem • Programming steps include: • Creating program specifications • Designing the application • Writing source code • Compiling/Interpreting programs • Executing (running) program Introduction to Computers & Java

16. Program Development (Programming) Cycle… • Creating program specifications – the requirements the application must meet Introduction to Computers & Java

17. Program Development (Programming) Cycle… • Designing the application – create file formats, screen layouts, and algorithms • Algorithm – a sequence of procedures, programming code, or commands that are used as part of a program or result in a program • Tools used in designing the sequential and logical structure of a program include: • Flowchart – uses symbols for program design • Pseudocode – uses natural English for program design Introduction to Computers & Java

18. Program Development (Programming) Cycle… • Writing source code – the code must be written, tested and debugged • Source code (file) – the file with the actual code which is written with a programming language of choice in a text editor • Debugging – the process of going through program code to locate and fix errors such as: • Syntax errors – grammatical mistakes in program language use • Logical errors – logical mistakes in a program Introduction to Computers & Java

19. Program Development (Programming) Cycle… • Compiling/Interpreting programs – the source code is translated in its entirety at one time (compiled) or a single line at a time (interpreted) from high-level program instructions into machine language, and executed if no errors are found (run) Introduction to Computers & Java

20. Program Development (Programming) Cycle… • Compiling/Interpreting programs • Compiler – a system software program that translates an entire high-level program (source code) at one time into machine language (object code grouped together in files called library files) that the computer can interpret and execute • It gives no feedback until the entire program has been compiled • Interpreter – a system software program that translates a single line at a time in a program • An immediate feedback is given if the code contains an error Introduction to Computers & Java

21. Program Development (Programming) Cycle… • Executing (running) program – the compiled or interpreted code is executed if no errors are found • Executable code – a linker or link editor resolves object code references to other programs by creating an executable code. Introduction to Computers & Java

22. Programming Languages • Invented to ease the task of programming with the use of words instead of binary numbers • Programming languages have evolved in generations and are improved over the years • The generations of programming languages include: • Low-level languages • High-level languages Introduction to Computers & Java

23. Programming Languages… • Low-level languages – include: • Machine language (1st Generation) – instructions are coded as a series of 0s and 1s and are unique to a particular computer • Assembler language (2nd Generation) – instructions are coded using some recognized symbols called mnemonics (memory aids) and are also unique to a particular computer • Example: MUL is used to represent a multiply instruction. An assembler translates the mnemonics into 0s and 1s Introduction to Computers & Java

24. Programming Languages… • High-level languages – programs instructions are often written in English-like expressions in languages such as: • 3rd Generation languages – instructions are coded at the programmer’s convenience but cannot be executed in their original form (source code) • A compiler or interpreter is needed to translate the language syntax into low-level machine language to be executed. • Examples include: FORTRAN (FORmulaTRANslator)-1955, Pascal-1968, C-1972, C++-1980s, Java-1990 • 4th Generation languages – Has a graphical user interface (GUI) that combines a code editor, compiler, debugger, linker, and executor into a single Inter-Development Environment (IDE). • Examples include: Visual Basic, Delphi, PowerBuilder, Visual.NET, etc Introduction to Computers & Java

25. Programming Language Elements • Every programming language uses the following general program elements: • Syntax – rules of a programming language • Comments – non executing programming language statements • Constant data – raw data used in programming such as numbers, strings, etc • Data output – displaying data on a screen or sending data to a file • Data input – receiving data from the keyboard or file • Variables – named memory locations for data storage Introduction to Computers & Java

26. Programming Language Elements… • Other programming language elements include: • Data types – specifies the types of data native to the programming language • Keywords – words with a special meaning in the programming language • Operators – symbols or words that perform operations on operands • Selections (Condition testing) • Repetitions (Looping structures) • Arrays • Files/Databases Introduction to Computers & Java

27. Methods of Programming • Two primary methods of programming are: • Procedural – creates programs made up of variables and procedures • Variable – named storage location in a computer’s memory • Procedure – set of programming language statements that perform a specific task • Object-oriented – creates programs made up of objects (instances of a class) • Object – a software entity with attributes (fields) and procedures (methods) • Class – specifies the attributes and methods of objects Introduction to Computers & Java

28. Principles of Object-Oriented Programming (OOP) • Encapsulation – grouping data (fields, methods, etc) into a single object • Information Hiding (Abstraction) – hiding an object’s data from other objects • The object’s methods are used directly access its data • Typically, the object’s data is hidden but allows its methods to be accessed • Inheritance – deriving classes (subclasses) based on other existing classes (superclasses) • Polymorphism - using the same procedure name or operator with different types of arguments • There are 2 types of polymorphism: overloading and overriding Introduction to Computers & Java

29. History of Java • In 1991 the Green Team was formed at Sun Microsystems to develop a hand-held device (named *7) to control home entertainment devices • James Gosling (the project leader) created the Oak language for the project • The Oak language translated programs into byte code for different processors • Oak (renamed Java) was later used to develop a Web browser named HotJava – which was able to download and run small Java programs known as applets • HotJava was demonstrated in 1995 which made Java popular • Netscape later incorporated Java into its Navigator browser Introduction to Computers & Java

30. Types of Java Programs • Two types of Java programs are: • Application – stand-alone programs that run on a computer • Applets – programs that are transmitted over the Internet from a Web server and executed on a Web browser Introduction to Computers & Java

31. Properties of Java • Object-Oriented – uses objects to perform specific tasks • Portable – enables programs to behave identical on different platforms like: Mac, Windows, Solaris (UNIX) • Compiles into byte code instead of machine language – the byte code is read by the Java Virtual Machine (JVM) – which interprets the code for different processors • “Architecture-neutral” – the byte code that comes out of the compiler will run on any processor and operating system • Can be embedded on Web pages – applets are downloaded and ran from Web pages • Secured – Web browsers run applets in a secure environment within a computer’s memory Introduction to Computers & Java

32. The Java Compiler & Java Virtual Machine (JVM) • Text editors are used to write Java programming statements (source code) and saved in a source file (.java extension) and translated (compiled) by a compiler • Compiler – program that translates source code into an executable form • Java compilers translate source code into a file (.class extension) containing byte code • The byte code instructions (not machine language) are executed by the Java Virtual Machine (JVM) • The JVM simulates a computer whose machine language is the Java byte code Introduction to Computers & Java

33. Java Program Development Process • The programmer uses a text edit to create a Java source code file (.java extension) • The programmer runs the compiler to translate the source code file into a byte code file (.class extension) • The Java Virtual Machine (JVM) reads and executes each byte code instruction Text Editor Source File Java Compiler Byte Code File Java Virtual Machine Introduction to Computers & Java

34. Java Editions • The software used to create Java programs is known as the Java Development Kit (JDK) or the Software Development Kit (SDK) • Some Java editions include: • Java Standard Edition (Java SE) – used for writing Java applications and applets • Java Enterprise Edition (Java EE) – used to create business client/server and Web server-based applications • Java Micro Edition (Java ME) – runtime-environment for consumer products like cell phones, pagers, etc Introduction to Computers & Java

35. Java Integrated Development Environments (IDE) • Consists of text editor, compiler, debugger, and other utilities integrated into a package • Current popular Java IDEs include: • Eclipse (http://www.eclipse.org) • NetBeans (http://www.netbeans.org) • IntelliJ IDEA (http://www.jetbrains.com/idea) • jGRASP (http://www.jgrasp.org) Introduction to Computers & Java

36. Compiling & Running Java Programs • javac is used to compile Java programs • E.g. javac Hello.java • A .class file is created if no are found • java is used to run Java programs • E.g. java Hello • Two types of errors (bugs) are: • Syntax errors – mistakes that violate the rules of the programming language • Logical errors – mistakes that cause programs to produce erroneous results Introduction to Computers & Java