EGR 141Computer Problem Solving in

Engineering and Computer Science

Data Types and Variables

Strings

“(248) 555-1212”“Hello, this is a string!”“The article ””Small Miracles”” is good”

“This is an example of a string in Visual Basic “ & _“that goes for more than one line. It can even “ & _“go on for three lines.”

“”

Empty StringStringContinuation

Quotes within a string

Strings

lblThetext.Text = “This is the caption for the control “ & _ “called lblThetext!”

String continuation

Strings

Putting the strings together…

lblText.Text = “Hello “ & txtName.Text & “!”

lblText.Text = “Hello txtName.Text !”

lblText2.Text = “Welcome “ & txtName.Text & _ “ to the Grand Hotel.”

Concatenation

CommentsBegin a comment with a ‘ mark

‘This is a commentlblText.Text = “Hello” ‘ Put Hello in the box

Program Header

‘Program: Lab 1 - Hello World‘Form: frmHello‘Programmer: Robin Bank‘Purpose: The user can enter their name and when‘ they click the ‘Show Message’ button‘ it will welcome them.

Variable Names

• VB Rules– <= 255 characters– must begin with an

alphabetic character– can't contain

punctuation characters (except underscore "_")

– must be unique within the same scope

– case insensitive– can't be the same as a

keyword

• Textbook Conventions– be meaningful and

descriptive– use consistent

abbreviations for same word

– use entire words or initial syllables

– use mixed case, with a capital letter at the start of each word ("camel-back notation")

– Generally between 5 and 20 characters.

Data Types

Data Types

Short. A non-decimal (whole) number with a value in the range of -32,768 to +32,767.

Integer. A non-decimal (whole) number with a value in the range of -2,147,483,648 to +2,147,483,647.

Long. A non-decimal (whole) number with a value in the range of -9,223,372,036,854,775,808 to +9,223,372,036,854,775,807.

Data Types

Data Types

Single. A floating-point (decimal) positive or negative number with a value in the range of up to 3.402823E38 (scientific notation).

Double. A floating-point (decimal) positive or negative number with a value in the range of up to 1.79769313486232E308.

Decimal. A decimal number with a value in the range of up to +79,228,162,514,264,337,593,950,335. without decimal precision and up to +7.9228162514264337593543950335 with 28 places of decimal precision.

String. Any number of alphabetic, numerical, and special characters.

Date. Dates in the range between January 1, 0001 to December 31, 9999 and times in the range between 0:00:00 to 23:59:59.

Boolean. The value True or False.

Data Types

Data Types

String. Any number of alphabetic, numerical, and special characters.

Date. Dates in the range between January 1, 0001 to December 31, 9999 and times in the range between 0:00:00 to 23:59:59.

Boolean. The value True or False.

Declarations

Dim MyNumber As LongDim MyDecimal As Double

Dim NumberA, NumberB, NumberC As Long

Dim message As StringDim fName, lName As String

Const PI As Double = 3.14159

Declarations

Built-in Constants

System.Drawing.Color.BlackSystem.Drawing.Color.RedSystem.Drawing.Color.LimeSystem.Drawing.Color.YellowSystem.Drawing.Color.BlueSystem.Drawing.Color.MagentaSystem.Drawing.Color.CyanSystem.Drawing.Color.White

Usage

Form1.ActiveForm.BackColor = System.Drawing.Color.Red

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Me.BackColor = System.Drawing.Color.Red

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Refers to the current, active form