Computer Basics Quiz

Book Title and Edition

• Starting Out with Java™ 7th Edition

Chapter

• Chapter 1: Introduction to Computers and Java

Chapter Topics

• Introduction
• Why Program?
• Computer Systems: Hardware and Software
• Programming Languages
• What is a program made of?
• The Programming Process
• Object-Oriented Programming

Java History

• 1991 - Green Team started by Sun Microsystems (now owned by Oracle)
• 7 handheld controllers for multiple entertainment systems
• Need for a programming language that runs on various devices
• Java (first named Oak) developed for this purpose

Introduction

• Java enabled web browser (HotJava) demonstrated at 1995 Sun World conference
• Java incorporated into Netscape shortly after
• Java is cross-platform; meaning it can run on various computer operating systems

Java Applications and Applets

• Java programs can be of two types:
  • Applications
    • Stand-alone programs that run without the aid of a web browser
    • Relaxed security model since the user runs the program locally
  • Applets
    • Small applications that require the use of a Java enabled web browser to run
    • Enhanced security model since the user merely goes to a web page and the applet runs itself

Why Program? (1 of 3)

• Computers are tools that can be programmed to perform many functions, such as:
  • Spreadsheets
  • Databases
  • Games
  • Word processing
• Computers versatile because they can be programmed
• Computer programmers implement programs that perform these functions

Why Program? (2 of 3)

• Aspects of a computer program that must be designed:
  • Logical flow of instructions
  • Mathematical procedures
  • Layout of programming statements
  • Appearance of the screens
  • Way information is presented to the user
  • Program's "user friendliness"
  • Manuals, help systems, and documentation

Why Program? (3 of 3)

• Programs must be analytically correct.
• Programs rarely work the first time.
• Programmers must analyze, experiment, correct, and redesign programs continuously.
• Programming languages have strict rules (syntax) that must be followed carefully.

Computer Systems: Hardware (1 of 2)

• Computer hardware components are the physical pieces of the computer
• Major hardware components of a computer:
  • Central processing unit (CPU)
  • Main memory
  • Secondary storage devices
  • Input and output devices

Computer Systems: Hardware (2 of 2)

• Diagram illustrating the relationships between computer hardware components (Input, CPU, Memory, Storage, Output)

Computer Systems: Hardware

• Main Memory (1 of 3)
  • Commonly known as Random Access Memory (RAM)
  • RAM contains currently running programs, and data used by those programs
  • RAM is divided into units called bytes
  • A byte consists of eight bits that may be either on or off

Computer Systems: Hardware

• Main Memory (2 of 3)
  • A bit is either on or off
    • 1 = on , 0 = off
  • Bits form a pattern representing a character or number
  • Each byte in memory is assigned a unique number (address)
  • RAM is volatile; when the computer is turned off, the contents of RAM are erased

Computer Systems: Hardware

• Main Memory (3 of 3)
• Main memory can be visualized as a column or row of cells
• A section of memory is called a byte
• A byte is made up of 8 bits
• A section of two or four bytes is often called a word

Computer Systems: Hardware

• Secondary Storage Devices
• Secondary storage devices are capable of storing information for longer periods (non-volatile)
• Common storage devices:
  • Disk drive
  • External drive
  • CD drive
  • Solid state drive
  • USB drive
  • DVD drive

Computer Systems: Hardware

• Input Devices
• Input is any data the computer collects from the outside world
• Data comes from input devices
• Common input devices:
  • Keyboard
  • Mouse
  • Scanner
  • Digital camera

Computer Systems: Hardware

• Output Devices
• Output is any data the computer sends to the outside world
• Data displayed on output devices
• Common output devices:
  • Monitors
  • Printers
• Some devices such as disk drives perform input and output, and are called I/O devices (input/output)

Computer Systems: Software

• Software refers to programs that run on a computer
• Two classifications of software:
  • Operating Systems
  • Application Software

Computer Systems: Software

• Operating Systems (1 of 2)
• An operating system is a set of programs that manages the computer's hardware devices and controls their processes.
• Most modern operating systems are multitasking

Computer Systems: Software

• Operating Systems (2 of 2)
• A multitasking operating system can run multiple programs at once
• Techniques are called timesharing
• A multitasking system divides the allocation of hardware resources and the attention of the CPU among all executing programs
  • Unix
  • Linux
  • MacOS
  • Windows

Computer Systems: Software

• Application Software
• Application software makes the computer useful to the user
• Application software provides a specialized environment for the user to work in
• Common application software:
  • Spreadsheets
  • Word processors
  • Accounting software
  • Tax software
  • Games

Programming Languages (1 of 5)

• A program is a set of instructions a computer follows to perform a task.
• A programming language is a special language used to write computer programs.
• A computer program is a set of instructions that enable the computer to solve a problem or perform a task
• Collectively, these instructions form an algorithm

Programming Languages (2 of 5)

• An algorithm is a set of well-defined steps to completing a task.
• Steps in an algorithm are performed sequentially.
• A computer needs the algorithm to be written in machine language.
• Machine language is written using binary numbers.
• The binary numbering system (base 2) only has two digits (0 and 1).

Programming Languages (3 of 5)

• Binary numbers are encoded as machine language
• Each CPU has its own machine language
  • Motorola 68000 series processors
  • Intel x86 series processors
  • ARM processors, etc.
• Example of a machine language instruction: 1011010000000101

Programming Languages (4 of 5)

• In the past, programmers wrote programs in machine language.
• Programmers developed higher-level programming languages to make things easier
• The first of these languages was assembler.
• Assembler made things easier, but was also processor-dependent

Programming Languages (5 of 5)

• High-level programming languages followed, that were not processor dependent
• Some common programming languages:
  • Java
  • BASIC
  • COBOL
  • Pascal
  • C
  • C++
  • C#
  • PHP
  • Visual Basic
  • Python
  • Ruby
  • JavaScript

Programming Languages

• Common Language Elements
• Some concepts common to virtually all programming languages:
  • Keywords
  • Operators
  • Punctuation
  • Programmer-defined identifiers
  • Strict syntactic rules

Programming Languages

• Sample Program (1 of 2)
• Sample Java code (public class HelloWorld)

Programming Languages

• Sample Program (2 of 2)
• Key words in sample program: public, class, static, void
• Key words are lower case (Java is case sensitive)
• Key words cannot be used as programmer-defined identifiers
• Semi-colons end Java statements, however not all lines end a statement.

Programming Languages

• Lines vs Statements
• Differences between lines and statements when discussing source code
• Example: System.out.println(message); ; one Java statement spread across two lines.
• A statement is a complete instruction that causes the computer to perform an action.

Programming Languages

• Variables (1 of 3)
• Data in a Java program is stored in memory
• Variable names represent a location in memory
• Variables in Java are sometimes called fields
• Variables are created by the programmer using a programmer-defined identifier
• Example: int hours = 40;

Programming Languages

• Variables (2 of 3)
• Variables are simply a name given to represent a place in memory

Programming Languages

• Variables (3 of 3)
• JVM (Java Virtual Machine) decides where the value will be placed in memory.

The Compiler and the Java Virtual Machine (1 of 4)

• Programmer writes Java programming statements for a program, known as source code.
• A text editor is used to create and save the Java source code file.
• Source code files have a .java extension.
• A compiler is a program that translates source code into an executable form.

The Compiler and the Java Virtual Machine (2 of 4)

• A compiler is run using a source code file as input.
• Syntax errors in the program are found during compilation.
• Syntax errors are mistakes that violate the programming language rules.
• The compiler creates another file containing translated instructions.

The Compiler and the Java Virtual Machine (3 of 4)

• Most compilers translate source code into executable files with machine code.
• The Java compiler translates a Java source file into bytecode instructions.
• Bytecode instructions are the machine language of the Java Virtual Machine (JVM).

The Compiler and the Java Virtual Machine (4 of 4)

• Bytecode files have a .class extension.
• The JVM is a program that emulates a microprocessor.
• The JVM executes instructions as they are read.
• JVM is often called an interpreter.
• Java is often referred to as an interpreted language.

Program Development Process

• Diagram showing the process of Java program development (text editor -> Save Java Statements -> Java compiler -> produces byte code -> JVM executes)

Portability (1 of 3)

• Portable means a program written on one type of computer can run on many computers with little modification.
• Java bytecode runs on the JVM, not the CPU. Java programs are highly portable.
• JVMs exist on many platforms
  • Windows
  • Unix
  • BSD
  • MacOS
  • Linux
  • etc.

Portability (2 of 3)

• With most programming languages, portability is achieved by compiling a program for each CPU it will run on.
• Java provides a JVM (Java Virtual Machine) for each platform, so programmers don't need to recompile for different platforms.

Portability (3 of 3)

• Diagram showing bytecode (.class) running on multiple Java Virtual Machines for various platforms

Java Versions

• Java Development Kit (JDK) is used to write Java programs.
• Different editions of JDK:
  • Java SE (Standard Edition)
  • Java EE (Enterprise Edition)
  • Java ME (Micro Edition)
• Available for download at http://java.oracle.com

Compiling a Java Program

• The Java compiler is a command-line utility.
• The command to compile a program is javac filename.java.
• javac is the Java compiler.
• The .java file extension must be used.

The Programming Process (1 of 2)

• Steps of the programming process
  • 1. Clearly define what the program is to do
  • 2. Visualize the program running on the computer
  • 3. Use design tools to create a model of the program.
  • 4. Check the model for logical errors

The Programming Process (2 of 2)

• Steps of the programming process
  • 5. Enter the code and compile it
  • 6. Correct any errors found during compilation
  • 7. Run the program with test data for input
  • 8. Correct any runtime errors found while running the program
  • 9. Validate the results of the program

Software Engineering (1 of 3)

• Encompasses the whole process of crafting computer software
• Software engineers perform several tasks in developing complex software projects:
  • Designing
  • Writing
  • Testing
  • Debugging
  • Documenting
  • Modifying
  • Maintaining

Software Engineering (2 of 3)

• Software engineers develop:
  • Program specifications
  • Diagrams of screen output
  • Diagrams representing program components and the flow of data
  • Pseudocode
  • Examples of expected input and desired output

Software Engineering (3 of 3)

• Software engineers use special software designed for testing programs.
• Most commercial software applications are large and complex.
• Usually a team of programmers, not a single individual, develops them.
• Program requirements are thoroughly analyzed and divided into subtasks handled by individuals within a team.

Object-Oriented Programming (1 of 4)

• Object-oriented programming is centered on creating objects rather than procedures.
• Objects are a combination of data and procedures (methods) that manipulate that data.
• Data in an object are called attributes
• Procedures in an object are called methods.

Object-Oriented Programming (2 of 4)

• Diagram showing an object with attributes (data) and methods (procedures/behaviors)

Object-Oriented Programming (3 of 4)

• Object-oriented programming combines data and behavior via encapsulation
• Data hiding is the ability of an object to hide data from other objects in the program.
• Only methods of an object should be able to directly manipulate its attributes
• Other objects can manipulate attributes via an object's methods.
• This indirect access is a programming interface

Object-Oriented Programming (4 of 4)

• Diagram showing an object with attributes (data) and methods (procedures/behaviors) and a programming interface enabling other objects to interact indirectly.