vb 2008 express for engineers

Introduction to Visual Basic 2008 Express

For Engineers

Introduction to Visual Basic 2008 Express Edition

The Basic programming language was developed at Dartmouth in the early 1960’s.

Visual Basic was created by Microsoft in 1991. Visual Basic 2008 Express Edition is

similar to the original Visual Basic but is much more powerful. It can be downloaded

free from Microsoft at:

http://www.microsoft.com/Express/Download/

To do any of the example labs, you will need to download and install Microsoft’s

Visual Basic 2008 Express Edition.

The Integrated Development Environment (IDE) should look something like this:

Tool Box

Solution

Explorer

Properties Window

Blank Form

Menu and Tool Bars

http://www.microsoft.com/Express/Download/

Program Development Cycle

Our computer program is called a project, application or solution. Software refers to

a collection of instructions to tell the computer what we want done. The computer

only knows what the programmer tells it to do. The programmer must know how to

solve the problem. The programmer will need to determine the output desired, that

is the Graphic User Interface (GUI). Then the programmer needs to determine what

input is required to get the desired output. Next the programmer needs to

determine the processing needed to take the input and end up with the desired

output.

Note, we determine the output first, then the input and then the processing. There

are several tools used by programmers to design a solution to the problem.

Programming Design Tools

Flowcharts (graphic)

Pseudo code (similar to computer code)

Hierarchy Charts (graphical)

Algorithms (list of steps)

You can look up each for more detail. We don’t need to use any of these tools for

our programs.

Program Development Cycle

1. Define the problem

2. Design a solution using a programming tool if desired

3. Create the interface (GUI)

4. Set the properties

5. Write the code

6. Run, test and debug

7. Add any documentation

We will concentrate on steps 3, 4 and 5.

Visual Basic Controls

Visual Basic has many controls and they are found in the toolbox which is usually

on the left side in the IDE.

They can be added to the form by double clicking the control or drag and drop the

control from the toolbox to the form. You can also single click the control, point

where you want the control and stretch to the size you want. We will look at four

controls.

Default names are TextBox1, Button1, Label1 and ListBox1.

Controls have events, properties and methods. The Text Box control is usually used

for input or output. When it is used for output, the Read Only property is usually set

to True. The caption on the Button Control should indicate the effect of clicking the

button. Setting the Text property determines the caption on the button. The Label

Control is used for information. It is usually used to explain the contents of a text

box. Setting the Text property determines the caption in the label. By default, the

Auto Size property is set to True. You will need to set the property to False to be

able to resize the control manually. The List Box control can be used to display

several pieces of information (output). It can be also used to select an item from a

list (input). Programmers usually name their controls with a name that something

to do with its use. They may also prefix the control name based on the type of

control.

Visual Basic Events

An event is an action, such as the user clicking a button. That would be a button

click event. Usually nothing happens in a Visual Basic program until the user does

something that generates an event. What happens depends on how the code is

written by the programmer. The user does something to a control, sometimes

referred to as an object. Visual Basic is an object-oriented language. When the user

does something to an object or control, an event is generated. Sometimes Visual

Basic is called an event-driven language. Each control may have many events and

many are the same for other controls. The default event for button and a label is

the click event. The default event for a text box is the text changed event. The

default event for a list box is selected index change event. The default event for the

form is the form load event. The form load event takes place when the user runs a

program. The programmer can write code for any event.

The code for these event procedures look like this:

Public Class Form1

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As

System.EventArgs) Handles Button1.Click

End Sub

Private Sub Label1_Click(ByVal sender As System.Object, ByVal e As

System.EventArgs) Handles Label1.Click

End Sub

Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e

As System.EventArgs) Handles TextBox1.TextChanged

End Sub

Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object,

ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged

End Sub

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As

System.EventArgs) Handles MyBase.Load

End Sub

End Class

As you can see, the general form is:

Control name_event

The easy way to start an event procedure is to double click the control on the form

in the IDE. This will automatically place something like the above code into the code

window.

The form looks like this:

Numbers

Much of the data processed by computers consist of numbers. The number are

called numeric literals. Numeric literals can NOT contain commas, a dollar sign, a

percent sign or mixed numbers like 8 ½. We use arithmetic operators to process the data.

Arithmetic operators

() used to change the order of operations

^ raises a number to the power of another number

* mutiplies two numbers / devides two number

+ adds two numbers

- subtracts two numbers

A variable is a letter or a name that can store a value in the computers memory.

You can declare a varible by telling the name and the type of varible you want to use. You can assign a value to the variable. You can use a variable by retrieving the

value held by the variable. There are many data types in Visual Basic. Double data

type goes to about 10308. Interger data type goes to about 109 and Single data type goes to about 1038.

We declare a varible with the Dim statement.

Dim speed As Single

Dim time As Single

Dim distance As Double

Or

Dim speed, time As Single, distance As Double

We assign a value to the variable by an assignment statement.

speed = 50

time = 2

We use these variables in a numeric expression.

distance = speed * time

The variable distance will have the value of 100.

Input and Output

A text box can be used for input or output. The content of a text box is stored in

the text property and is always a string. A string is a sequence of characters which

could be letters, numbers or other characters.

Input example:

speed = TextBox1.Text

Now if the text property of TextBox1 contained the number 50, it would actually be

the string 50. Now I can’t multiply strings but I can multiply numbers. There is a

built-in function that will convert the string “50” to a number 50. The function is the

Val function. We will rewrite the code.

speed = Val (TextBox1.Text)

Now the variable speed contains the number 50 and I can perform mathematic

operation with it. We are reading what is already stored in the text box and placing

the value into the variable speed. The function CDbl will convert the string to a

double data type. The function CSng will convert the string to a single data type.

There are many built-in functions.

Notice the format: TextBox1.Text is Control name.Property

Output example:

TextBox1.Text = speed

Here the variable speed already contains a value and we are setting the text

property of the text box. Even if the value in the variable was a number, the value

in the text property of the text box will be a string.

A list box can be used for output but we used the add method to add items to the

collection displayed in the list box.

ListBox1.Items.Add (speed)

Notice the method Add, is preceded with a period and followed with an argument in

parentheses.

Now let us create our first program. We want to write a program that will convert

meters to feet. We will need one input and one output. Now let us look at some

steps to creating a Visual Basic project, solution or application.

Steps in creating a Visual Basic application

Step 1

Create an interface with 2 labels, 2 text boxes and a button.

Step 2

To set the property, single click the control and in the properties window, select the

property that you want to change.

Control Property Value

Label1 Text Enter meters

Label 2 Text Converted to feet

Button1 Text Calculate

Form1 Text Convert

I set many other properties but you don’t have to.

Also set the TabIndex property of TextBox1 to 0. This will make the cursor be in the

textbox and be ready for the user to type in a value.


Label1 AutoSize FALSE

Label 2 AutoSize FALSE

Label1 Location

x 25

y 45

Label2 Location

x 25

y 135

Label1 Size

Width 110

Height 20

Label2 Size

Width 110

Height 20

TextBox1 Size

Width 110

Height 20

TextBox2 Size

Width 110

Height 20

Form1 Size

Width 300

Height 300

Form1 StartPosition CenterScreen

TextBox1 Location

x 165

y 45

TextBox2 Location

x 165

y 175

Step 3

Write the code for the button click event. Double click on the button while in the

IDE. The code window will open. Type in the following code:

Public Class Form1


System.EventArgs) Handles Button1.Click Dim m, ft As Single

m = Val(TextBox1.Text) ft = 3.2808 * m

TextBox2.Text = ft End Sub

End Class

Now run the program by pressing F5. Type 10 into TextBox1. Click the button. The

answer (32.808) should be displayed in TextBox2. Always check you run to make

sure it gives the correct answer. There is nothing worse than a program that gives

wrong answers. The run should look like this:

After stopping your run, pull down the File menu and select Save All. This will save

all the files needed for this project. There are many files, not just one file. We

created the GUI, set some properties and wrote some code. Visual Basic is

sometimes called RAD- Rapid Application Development system.

Now let us create our next program. We want to computer the flow in a pipe or duct

given the cross sectional area and the velocity.

Q = AV

Q = flow (ft3/sec)

A = area (ft2)

V = velocity (ft/sec)

We will have two inputs and one output.

Step 1

Create an interface with 4 labels, 3 text boxes and 1 button. It should look

something like this:

Step 2

Set the following properties:

It should look something like this:


Label1 Text Enter the area in square feet

Label2 Text Enter the velocity in ft / sec

Button1 Text Compute

Label3 Text The flow is:

Label4 Text cu ft / sec

Form1 Text Flow

Double click on the button while in the IDE. The code window will open. Type in the

following code:

Public Class Form1



Dim area, vel, flow As Single

area = Val(TextBox1.Text)

vel = Val(TextBox2.Text)

flow = area * vel

TextBox3.Text = flow

End Sub

End Class

The run (press F5) should look something like this:

Be sure to save all if you get the same answers. If you don’t get the same answers,

check your code for mistakes or the values entered during the run.

I set the TabIndex property of the controls as follows:

When the TabIndex property is set to 0, the cursor will start there. When you press

the Tab key it will move to the next number (1). Press the Tab key again and it

moves to the next number (2) which is the button. You can run this entire program

without using the mouse. Would you rather be fast or half fast? Any time you can

use the keys on the keyboard you will be faster than using the mouse.

Again, we created the Graphic User Interface (GUI). We added labels, text boxes

and a button. Then we set a few properties. Then we wrote a little code. We could

change the program to handle something like:

E = IR

E = voltage

I = current (amps)

R = resistance (ohms)

Or something like:

A = LW

A = area (square feet)

L = length (feet)

W = Width (feet)

I changed many other properties but you only need to set a few properties.


Label1 Location

x 30

y 25

Label2 x 30

y 60

Label3 x 30

y 170

Label4 x 340

y 170

TextBox1 x 290

y 25

TextBox2 x 290

y 60

Button1 x 181

y 111

TextBox3 x 181

y 170

Form1 Size

Width 500

Height 300


Built-in Functions (Math)

Visual Basic has many different types of built-in functions like string functions,

conversion function and math functions. Engineers often use math functions so we

will look at the once available in Visual Basic.

Action Function

Derive trigonometric functions. Atn, Cos, Sin, Tan

General calculations. Exp, Log, Sqr

Generate random numbers. Randomize, Rnd

Get absolute value. Abs

Get the sign of an expression. Sgn

Perform numeric conversions. Fix, Int

We can derive many other functions as user defined functions:

Function Derived function

Secant (Sec(x)) 1 / Cos(x)

Cosecant (Csc(x)) 1 / Sin(x)

Cotangent (Ctan(x)) 1 / Tan(x)

Inverse sine (Asin(x)) Atan(x / Sqrt(-x * x + 1))

Inverse cosine (Acos(x)) Atan(-x / Sqrt(-x * x + 1)) + 2 *

Atan(1)

Inverse secant (Asec(x)) 2 * Atan(1) – Atan(Sign(x) / Sqrt(x *

x – 1))

Inverse cosecant (Acsc(x)) Atan(Sign(x) / Sqrt(x * x – 1))

Inverse cotangent (Acot(x)) 2 * Atan(1) - Atan(x)

Hyperbolic sine (Sinh(x)) (Exp(x) – Exp(-x)) / 2

Hyperbolic cosine (Cosh(x)) (Exp(x) + Exp(-x)) / 2

Hyperbolic tangent (Tanh(x))

(Exp(x) – Exp(-x)) / (Exp(x) + Exp(-

x))

Hyperbolic secant (Sech(x)) 2 / (Exp(x) + Exp(-x))

Hyperbolic cosecant

(Csch(x)) 2 / (Exp(x) – Exp(-x))

Hyperbolic cotangent (Coth(x))

(Exp(x) + Exp(-x)) / (Exp(x) – Exp(-

x))

Inverse hyperbolic sine (Asinh(x))

Log(x + Sqrt(x * x + 1))

Inverse hyperbolic cosine (Acosh(x))

Log(x + Sqrt(x * x – 1))

Inverse hyperbolic tangent (Atanh(x))

Log((1 + x) / (1 – x)) / 2

Inverse hyperbolic secant (AsecH(x))

Log((Sqrt(-x * x + 1) + 1) / x)

Inverse hyperbolic cosecant (Acsch(x))

Log((Sign(x) * Sqrt(x * x + 1) + 1) /

x)

Inverse hyperbolic cotangent (Acoth(x))

Log((x + 1) / (x – 1)) / 2

Pi (3.141592654) is built in to Excel but not Visual Basic.

Now let us look at our next program. We want to calculate the angle a road should

be banked when given the velocity, radius of curvature and the force of gravity.

Visual Basic uses radians when using trigonometric functions. To convert from

radians (R) to degrees (D), we use:

Step 1

Create an interface with 5 labels, 3 text boxes, 3 buttons and one list box. The

interface should look something like this:

Step 2

Set some of the properties of the controls.

Notice, there is a “&” character in front of some letters. This will make the letter

underlined and an access key or hot key. The user can press the Alt key and the

letter (Alt + p) to select the button without the use of the mouse. To get 2, I held

down the Alt key while typing the numbers 253 on the numeric key pad. Then let

up on the Alt key.

The interface should look something like this:


Label1 Text Enter the velocity of the car in ft / sec

Label2 Text Enter the radius of the curve in feet

Label3 Text Enter the force of gravity (earth is 32.2 ft / sec²)

Label4 Text The angle of the banked road is:

Label5 Text degrees

Button1 Text Com&pute

Button2 Text &Quit

Button3 Text &Clear

Step 3

Now, we need to write the code (event procedures) for three buttons. Again, double

click the compute button while in the IDE. The code window should open. Type in

the following code:



Dim vel, rad, grav, trad, tdeg, pi

vel = Val(TextBox1.Text)

rad = Val(TextBox2.Text)

grav = Val(TextBox3.Text)

trad = Math.Atan(vel ^ 2 / (rad * grav))

pi = 3.141592654

tdeg = 180 * trad / pi

ListBox1.Items.Add(tdeg)

End Sub

Press F5 and your run should look something like this:

If you get the same answer, GREAT! If you get something different, check your

code or the numbers you typed in during the run.

In the IDE, click on the Form1.vb [Design] tab. Now double click on the Quit button

and the code window should open. Now we want to add code to the Button2 Click

event. Add the following code:



Me.Close()

End Sub

Here we are using the close method. Me refers to Form1. Therfore, we are saying close the form which ends the run. Remember I said controls or objects have

properties, events and methods. Note, we used the Add method to add items to the

list box. So a method has a period in front and parenthesis at the end.

We could have used the End statement. This ends the run which also closes the

form. The code would look something like this: Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As


End

End Sub

Now click on the Form1.vb [Design] tab. Double click on the Clear button. This

should open the code window so you can write the following code. Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As


TextBox1.Text = ""

TextBox2.Clear()

TextBox3.Text = ""

ListBox1.Items.Clear()

End Sub

For text box 1, I set the text property to a null string (a string with nothing in it).

For text box 2, I used the clear method. You can use either one for a text box. For

list box 1, I used the clear method. A list box does NOT have a text property.

As before, I set many other properties. I set the StartPosition property to

CenterScreen. I set the size of the text boxes to 125, 20. I set the size of the buttons to 110, 25. I set the Form1 size to 550, 400. I set the size of three of the

labels to 300, 25. I set the Location, x value to 35 for three of the labels. I set the

Location, x value of the three text boxes to 385. I set the x and y values of all the controls or objects.

I also set values of the TabIndex of all the controls as shown:

Remember, the user can press the Tab key to navigate from text box 1 (number 0) to text box 2 (number 1) all the way to the Quit button and never use the mouse.

Remember, using the mouse is not as fast. The user can also use the hot key, (p, q

and c). They can hold the Alt key and press p (Alt + p) and it will be the same as

clicking on the Compute button. They can press Alt + q and it will be the same as clicking the Quit button and Alt + c for the clear button.

Be sure to save all when you finish your run and finish setting all the properties. I created the following folders:

C:\Visual Basic 2008\Projects

In the projects folder, I now have three folders for Lab1PDH, Lab2PDH and

Lab3PDH. This was Lab3PDH. In the following path:

C:\Visual Basic 2008\Projects\Lab3PDH\Lab3PDH\bin\Debug

There is a Lab3PDH.exe file. This is the file you can send to your friends and they

can run it if they have Microsoft Net Framework 3.5. It is free and you installed it

when you installed Visual Basic 2008 Express Edition. As you can see many files are

created when you create a Visual Basic Project.

Loops

There are several tyoes of loops used in Visual Basic.

While … End While Do … Loop

For … Next

For … Each Next

The For … Next loop performs the loop a set number of times. It uses a control

variable or counter to keep track of the number of repetions. You specity the

starting value and the end value. The default increment is one. You can specify the increment. The format looks something like this:

For counter [ As datatype ] = start To end [ Step step ]

[ statements ]

[ Exit For ]

[ statements ]

Next [ counter ]

The items in [] are optional.

Examples of For statements:

Now our next program will produce a table. We want the user to enter the value of a resistor in a text box. They will click the button to produce a table in a list box.

We will vary the current and compute the power. We will use the following

equation:

P = I2 R

P = Power (watts)

I = Current (amps)

R = Resistance (ohms or Ω)

Hold the Alt key while typing 234 on the numeric key pad to get Ω.

Step 1

Create the graphic user interface (GUI) with one label, one text box, one button

and one long listbox. The width of the form is 500 and the height is 600. The

interface should look something like this:

Step 2

Set properties as follows:

When we set the form Font property, that is the default font for controls placed on

the form. The label, text box, button and list box all have the same font unless we change it. This will be useful when we try to produce a table with characters that

line-up.

Set the following properties:


Form1 Font

Name Courier New

Size 10


Form1 Size

Width 500

Height 600


Label1 Size

Width 270

Height 23

Label1 Location

x 32

ListBox1 Location

x 32

ListBox1 Size

Width 425

Height 436

Label1 Text Enter the resistance in ohms

Button1 Text &Table

Button1 Size

Width 120

Height 26

The form should look something like this:

Step 3

Now we are about ready to write some code. The items placed in a list box are

string data type. We will use the String.Format method to add items to the list box.

The format or syntax is:

String.Format(format, arg0, arg1, arg2)

We will have three arguments (power, current and resistance). The format item in

the above has a certain format or syntax.

{index[,alignment or length][:format specifier character]}

We will not use the last item (format specifier character).

While in the IDE, double click the button and the code window should open.

Remember to set the TabIndex property of the textbox to 0 and the button to 1.

Write the following code:

Public Class Form1

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim p, i, r As Single, fm As String

r = Val(TextBox1.Text) fm = "{0,-15}{1,-15}{2,-15}"

ListBox1.Items.Clear() ListBox1.Items.Add(String.Format(fm, "Power", "Current", "Resistance"))

ListBox1.Items.Add(String.Format(fm, "watts", " amps", " Ω")) ListBox1.Items.Add(String.Format(fm, "", "", ""))

For i = 10 To 20 Step 0.5 p = i ^ 2 * r

ListBox1.Items.Add(String.Format(fm, p, i, r)) Next i

End Sub End Class

The first thing is to dimension all our variables. Then we store the value typed into

the text box in the variable r.

Looking at:

fm = "{0,-15}{1,-15}{2,-15}"

The 0, 1 and 2 are the index value of the three arguments. The -15 says you want

it left aligned and 15 characters long. The next four lines of code clear the list box

and display the heading for our table in the list box. The For … Next loop creates a

table of values in our list box.

Press F5 to run the program. The run should look something like this:

I we change the -15’s in, fm = "{0,-15}{1,-15}{2,-15}" , to 15 then the columns

will be right justified.

Again I held down the Alt key while typing the numbers 234 on the numeric key

pad to get the symbol Ω. There are many characters that can be entered this way.

It works with most fonts. This also works in Excel, PowerPoint and of course Word.

Special Characters:

Hold down the Alt key and type 237 from the numeric key pad only to get φ.

Hold down the Alt key and type 241 to get ±.

In engineering, we use the degree symbol a lot. Hold down the Alt key and type

248 to get something like this 27 °F. We also use square a lot. So how would I get

a² + b² = c². That is right Alt + 253. If you can find it on here, use it. That will be

much fast than any other way. In engineering, time is money. If we can save time,

we can make more money.

I hope we covered enough of Visual Basic 2008 to get you interested in learning

more. There are many new books on Visual Basic 2008, some you can download

free from the Internet. One is “Accelerated VB 2008”. Other good books are

“Beginning VB 2008 From Novice to Professional” and “Visual Basic 2008 Step by

Step”. There are many controls like radio buttons, check boxes, timer, combo

boxes, group boxes and picture boxes. that we didn’t cover. We didn’t discuss

strings in detail since engineers use number a lot. Arrays are another useful topic

for engineers. In addition to event procedures, there are sub and function

procedures.

vb 2008 express for engineers

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