Applicaiton_Design

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CPU255 - Introduction to ProgrammingLethbridge College 1

Week 4

Application DesignApplication Design

Agenda Application Design

5 Steps of Application Design

Pseudocode

TOE Chart Programming Conventions

Comments

Indentation

Line Continuation

Naming Conventions

Tutorial 2


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5 Steps of Application Design 5 steps to complete an application effectively

1. Plan the application

Flow charts/Pseudocode, TOE charts,Sketch user-interfaces (find what works foryou)

2. Build the Graphical User-Interface (GUI)

3. Code the application

4. Test and debug the application

5. Assemble the documentation

Help files, comments, technical report

Pseudocode (pg. 90) List of steps written in plain English that

describes what an object needs to do to performassociated tasks

The pseudocode solution is translated byprogrammers into a language (VB) thatcomputers can understand

Text Example Print Order Button (pg. 131)

1. Hide the command buttons on the form

2. Print the user form

3. Re-display the buttons on the form

4. Send the focus to the Clear Screen button


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TOE Chart (pg. 98) Tasks Objects Events

3 Steps:1. Identify the TASKS the application needs to perform

2. Identify the Objects required to complete the tasks

3. Identify the Events required to trigger an object intoperforming its assigned task

See pg. 98 for an example

Programming Conventions Developers follow certain conventions when they write

code

Conventions dictate naming and documentation styles

Helps other developers work with your code more easily

Will even help you!


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Conventions continued Common conventions for Visual Basic:

Comments

Indentation

Line Continuation

Naming Conventions

Comments Used to explain code (what it is doing)

In VB the apostrophe () is used

Anything after an is not interpreted by thecomputer

In your applications always include 3 thingsat the top of the main forms code:

1. Name:

2. Date:

3. Program Description:


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Comments Comments appear green by default

Comment/Uncomment a block of selected codeusing tools on the Edit toolbar

'Send a message to the userMsgBox "CPU255 - Introduction to Programming is fun!"

Comment block Uncomment block

Indentation Do This:

Dont do this:

Private Sub Command1_Click()

Dim x As Integer

For x = 1 To 3

y = 1 + x

Next x

End Sub

Private Sub Command1_Click()

Dim x As Integer

For x = 1 To 3

y = 1 + x

Next x

End Sub


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Line Continuation

VB allows you to break a long line of code over into thenext line

Use a space followed by an underscore ( _) at the pointyou want the line to break

This can be very useful to help improve your codereadability

Example:

Naming Conventions When adding a form or control VB assigns it a

default name

Example: the 1st Command Button added to a

form is named Command1, and the 2nd isCommand2

In this course, you must follow the namingconvention syntax for:

1. Controls

2. Forms

3. Variables (discussed next lecture)


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Naming Conventions continued Controls & Forms syntax

Prefix 3 lower case letters specify type Example: cmd Command Button

Remaining letters describe the control Example: Exit

Command1 cmdExit

Naming Conventions continuedQ What if there is more than one word used in

the naming convention?

txtFirstname

txtFirstName

A Capitalize FirstLettersOfWords.

Example:

a text box used to enter customers first name:


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Control Prefix Naming Conventions

Control Default Name Name Prefix

Check Box Check1 chk

Combo Box Combo1 cbo

Command Button Command1 cmd

Form Form1 frm

Frame Frame1 fra

Image Image1 img

Label Label1 lblList Box List1 lst

Option Button Option1 opt

Picture Box Picture1 pic

Text Box Text1 txt

Timer Timer1 tmr

More about Visual Basic

Things you need to know to complete Tutorial #2

Methods

Functions TabIndex Property

Access Keys

Concatenation Operators

Assigning Properties at run-time


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Methods

Methods are pre-defined procedures built intoobjects

They define the behaviour (or tasks) of objects

Examples of Methods used in Tutorial 2:

object.SetFocus

[form.]PrintForm

Built-In Functions Most programming languages come with a prewritten

set of functions

Functions are pre-defined procedures or routines

Similar to object methods, however functions return avalue

Two types of Functions:

1. Numeric Functions

2. String Functions


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Functions1. Numeric Functions:

Deal with ways of manipulating and converting numbers

2. String Functions: Deal with ways of manipulating and converting strings

String Functions used in Tutorial 2:1. Val()

2. Format()

Val() Function (pg. 143)

Used to translate a string into a number

Usage: Val(string) Example:

Val(10) Returns 10

Val(Kyle) Returns 0


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Format() Function (pg. 144)

Format(5459.4 , ##,##0.00) Returns 5,459.40

Format(1000000, currency) Returns $1,000,000.00

Used to format numbers, dates and times

Usage: Format(expression, format) Example:

TabIndex Property of Objects (object.TabIndex)

Permits the user to access active controls on

forms by pressing the Tab key Order of access is determined by predefined

order as set by the programmer

First object added to a form is assigned adefault TabIndexvalue of0


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Access Keys Allows users to select objects using the Alt key in

combination with a number or letter (must be unique) To set an access key place the ampersand (&) in the

caption property

Example:

&Save File E&xit

Access Keys continued

To set focus to a text box place the ampersand in thelabel controls caption property that precedes the textbox

Label control Text box

lblFirstName.Caption = &First Name:


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Concatenation Operators

Join multiple strings into a single string

The plus sign (+) and ampersand (&) can beused to concatenate strings

Example:

The & operator is recommended for stringconcatenation

Assigning Properties at Run-time

Assignment statements assign a value to a property(attribute) of an object

Syntax: [form.]object.property = value

Square brackets [] indicate optionalinformation

Italicized words indicate requiredinformation

The period between the object and the property iscalled the dot member selection property

What appears to the right of the period is a member ofwhat appears to the left


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CPU255 - Introduction to ProgrammingL thb id C ll 14

Getting Help F1 key for context-sensitive help

MSDN Library Visual Studio 6.0

World Wide Web

Hands-On Tutorial Tutorial 2

Lesson B Building the User Interface

Lesson C Coding, Testing, Debugging, andDocumenting the Application

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