1 INF160 IS Development Environments AUBG, COS dept Lecture 04 Title: Computer Applications (Extract from Syllabus)

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INF160 IS Development Environments AUBG, COS dept

Lecture 04Title:

Computer Applications (Extract from Syllabus)

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Lecture Contents:

Program – definition/description Application – definition/descriptionCategories of applicationsDemo programs/applications

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Demo Programs:

Group name: Test160aHelloWorldConsole Applications:

Test160aHelloWorldVBTest160aHelloWorldCPPTest160aHelloWorldC#Test160aHelloWorldJava

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Demo Programs:

Group name: Test160eGUI1GUI Applications:

Test160eGUI1VBTest160eGUI1CPPTest160eGUI1C#Test160eGUI1Java

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Demo Programs:


Test160eGUI2VBTest160eGUI2CPPTest160eGUI2C#Test160eGUI2Java

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Demo Programs:

Group name: Test160eGUI3GUI Applications: Java Applets

Test160eGUI3Java

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Program – definition/description

Program: An organized list of instructions that, when executed, causes the computer to behave in a predetermined manner.

A program is like a recipe. It contains a list of ingredients (called variables) and a list of directions (called statements) that tell the computer what to do with the variables. The variables can represent numeric data, text, or graphical images.

Without programs, computers are useless.

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Application – definition/description

Application: A program or a group of programs designed for end users.

Application software can be divided into two general classes: Systems software Application software.

for details, open next 2 slides

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Systems software consists of low-level programs that interact with the computer at a very basic level. This includes:

Operating Systems components,

Compilers or Language Processors,

Uutilities for managing computer resources.

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In contrast, application software (also called end-user programs) includes:

Data Base programs, Word processors,Spreadsheets etc.Figuratively speaking, applications software

sits on top of systems software because it is unable to run without the operating system and system utilities.

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Enterprise application

Enterprise application, or

Enterprise software, or

Enterprise Application Software (EAS) are all commonly used phrases i.e. synonyms to describe applications -- or software -- that a business would use to assist the organization in solving enterprise problems.

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Categories of applications – primitive elementary classified

Console Applications

Windows GUI Applications

Web based (Internet) Applications

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Categories of applications – more precise classification

Most IDEs come with a package of wizards that generate starting code for wide variety of applications

Console ApplicationsWindows GUI ApplicationsWeb based (Internet) ApplicationsServicesClass librariesOther special applications

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Console Applications Run in a command prompt And are text – only Reading from the keyboard Writing to the screen

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Windows GUI Applications Are graphical applications Use mouse and keyboard for generating events Use Windows controls such as labels, text boxes,

buttons, check boxes, radio buttons etc.

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Web based (Internet) Applications Run on a Web server When a particular URL is loaded Send HTML as response to a request from a

waiting browser

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Services Applications that run in the background And respond to requests But have no any visual user interface

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Class libraries Are collections of code that can be called by other

code. Static libraries (.lib, .a) Dynamic libraries (.dll)

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You can create several different types of programs using C#.

For example,

•.NET console application running on Windows.

•.NET graphical user interface (GUI) application running on Windows (desktop applications).

•ASP.NET web application running on Internet Information Services (IIS).

21C# Programming: From Problem Analysis to Program Design 21

Types of Applications Developed with C#

Web applications

Windows graphical user interface (GUI) applications

Console-based applications

Class libraries and stand-alone components (.dlls)

Smart device applications

Services


Types of Applications Developed with Java

Java programs may be applications or applets.

Applications are standalone programs, similar to .NET Console applications and/or Windows based GUI applications.

Applets are similar to applications, but they do not run as standalone programs.

- Instead, applets adhere to a set of conventions that lets them run within a Java-compatible browser (client-side).

- You can only run an applet from an HTML page.

2323Java Programming: From Problem Analysis to Program Design, 4e

INTRO to Graphical User Interface (GUI) Components

Computing Process models I P O Client Server

JAVA I-P-O Applications classified: Console applications

• Input data, output data displayed in MSDOS window Windowed applications

• Using dialog boxes for input/output (class JOptionPane and methods) Windows based GUI applications

• Using Swing class library components: windows, labels, text fields, buttons etc.


INTRO to Graphical User Interface (GUI) Components

Drawbacks/disadvantages of Console applications Dialog boxes based windowed applications

Suppose, the user/developer wants the program to display all input data and output data in one pane or window or dialog box

Java calls such a dialog box GUI or simply UI


Graphical User Interface (GUI) Components

Advantages of using GUI: View inputs and outputs simultaneously One graphical window Input values typed in any order Change input values in window Click on buttons to get output


Graphical User Interface (GUI) Components

Terminology:Frame

Title bar• System supported icons

• Title Content pane

• Components – labels, text fields, buttons etc

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Web based (Internet) Applications

C

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Web Applications

C# Programming: From Problem Analysis to Program Design 28

Figure 1-14 Web application written using C#


Web Applications (continued)

C# was designed with the Internet applications in mind

Can quickly build applications that run on the Web with C#

Using Web Forms: part of ASP.NET

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Windows GUI Applications

C


Windows Applications

Applications designed for the desktop

Designed for a single platform

Use classes from System.Windows.Form

Applications can include menus, pictures, drop-down controls, buttons, text boxes, and labels

Use drag-and-drop feature of Visual Studio


Windows Applications (continued)

Figure 1-15 Windows application written using C#

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C



Normally read input data from the keyboard

Display text on the command console

Easiest to create

Simplest approach to learning software development

Minimal overhead for input and output of data

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Demo Programs:

Console Applications:

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Demo Programs:


Test160aHelloWorldVB Source text Demo execution

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Demo Programs:


Test160aHelloWorldCPP

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Demo Programs:


Test160aHelloWorldC#

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Demo Programs:


Test160aHelloWorldJava

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Demo Programs:

GUI Applications:

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Demo Programs:


Test160eGUI1VBTest160eGUI2VB

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Demo Programs:


Test160eGUI1CPPTest160eGUI2CPP

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Demo Programs:


Test160eGUI1C#Test160eGUI2C#

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Demo Programs:


Test160eGUI1JavaTest160eGUI2Java

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Java Demo Programs:

GUI Applications:

Pure empty frame displayed

PureFrame.java

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Java Demo Programs:

GUI Applications:

Frame includes: 3 labels, 3 text boxes, 2 buttons

Proben14.java

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Demo Programs:

JAVA Applets:

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Demo Programs:

Group name: Test160eGUI3GUI Applications: Java Applets

Test160eGUI3Java

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Demo Programs:

Applets:

Pure empty frame displayed using AppletViewer utility

WelcomeApplet.java

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Demo Programs:

Applets:

Pure empty frame displayed using Web browser utility

WelcomeApplet.javaWelcomeApplet.html

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Demo Programs:

Applets:

Frame includes 2 labels, 2 textfields and displayed using AppletViewer utility

TempConvertApplet.java

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Demo Programs:

Applets:

Frame includes 2 labels, 2 textfields and displayed using Web browser utility

TempConvertApplet.javaTempConvertApplet.html

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Thank You For

Your Attention!

54Java Programming, Fifth Edition 54

Introducing Applets

Applets Java programs called from within another

application Frequently run from a Web page Display as rectangular area Can respond to user-initiated events Behaviors come from Java class named JApplet


Introducing Applets (continued)

Similar to Java application .java file extension Compile into bytecode using the javac command Saved with .class extension Can contain:

• Methods you define

• Variables and constants

• Decisions, loops, and arrays

• GUI elements

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Introducing Applets (continued)

Different from a Java application Descend from the JApplet class Run from another application

• Do not use the java command to execute an applet Do not contain a main() method Do not set a default close operation Cannot delete, read, or create files on the user’s system Cannot run any other program on the user’s system

Java Programming, Fifth Edition 56

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Understanding the JApplet Class

Import JApplet import javax.swing.JApplet;

JApplet Swing class

Skeletal structure of a typical Applet


import java.awt.Graphics;import javax.swing.JApplet;public class WelcomeApplet extends JApplet{

}

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Running an Applet

Run applet from a document usually in HTMLHTML, or Hypertext Markup Language

Simple language used to create Web pages for the Internet Contains many commands

Run an applet In a Web browser Applet Viewer

•appletviewer command



Writing an HTML Documentto Host an AppletWhen you create an applet

Write applet in Java• Save with .java file extension

Compile applet into bytecode using javac command Write HTML document

• Includes statement to call compiled Java class Load HTML document into a Web browser

• Or run Applet Viewer program


Writing an HTML Documentto Host an Applet (continued)Web browser

Program allows display of HTML documents Often contains Java applets

Untrusted code Carries possibility of doing harm Applet code not trusted

Sandbox Safe area in which applet code can run


Writing an HTML Documentto Host an Applet (continued)Run applet from within HTML document

<HTML>

<object code="AClass.class" width=300 height=200> </object>

</HTML>

Three object tag attributes code

• Name of compiled applet width height


Writing an HTML Documentto Host an Applet (continued)

Pixels Control size of applet Set with width and height Tiny dots of light

• Make up image on video monitor

Tag set <applet> and </applet> Use instead of <object> tag Better to use <object> tag


Creating a JApplet Containingan init() Method

JApplet class methods Invoked by Web browser when browser runs applet public void init() public void start() public void paint() public void stop() public void destroy()

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Creating a JApplet Containingan init() Method (continued)



Understanding the JAppletLife Cycle

Applets are popular Easy to use in Web pages

JApplet class Contains methods automatically called by browser

•init()•start()•stop()•destroy()


Understanding the JAppletLife Cycle (continued)

init() method Executes when Web page containing a JApplet

loaded Or when running appletviewer command

start() method Executes after init() method Executes again every time applet becomes active

after it has been inactive



stop() method Invoked when user leaves Web page

destroy() method Called when user closes browser or Applet Viewer Releases any resources JApplet might have

allocated

Every JApplet has the same life cycle outline

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69Java Programming: From Problem Analysis to Program Design, 4e 69

Differences Between Applets and GUI Applications

Applets Class extends JApplet No main method Uses init method Displayed by HTML Sets title in HTML Size set in HTML Applet closes when HTML

doc closes

GUI applications class extends JFrame Invokes main method Uses constructors Uses method setVisible Uses setTitle method Uses method setSize Closes with Exit button

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1 INF160 IS Development Environments AUBG, COS dept Lecture 04 Title: Computer Applications (Extract from Syllabus)