Console Application – Chapter one

Objectives of the Chapter

· Starting the console application

· Learning basic functions

· Get started with basic programs

· Understand the coding in VS.net

Starting the console based program in Visual Studio.net

Follow the following steps to run the console based application.

1. Run Microsoft Visual Studio 2005 or other versions. (Start-programs-Microsoft Visual Studio2005-Microsoft Visual Studio 2005)

2. From file, select new project…

3. In the project type-select windows and chose console application in the template. Give the name of your project at the bottom. Choose ok.

Then you will see the basic structure of a VB.Net Console based Program.

Module Module1

Sub Main()

End Sub

End Module

Some basic programs and side by side understanding functions

Here is the most basic program…

Module Module1

Sub Main()

System.Console.Write("console") 'This line traces the word console

System.Threading.Thread.Sleep(2000) 'This line stops the program for 2 seconds before ending

End Sub

End Module

To run the program press F5 key or click the green play button on the tool bar.

Description:-

By default your program will start with the object module1. (If you want, you can change the module name. i.e. module module_name. Then you will have to select the first object to be executed. For this, on the solution explorer panel, right click your project name and select properties. Then select the desired module name in the startup object.)

Sub main is the main function of your program. This main function must always appear in your program. Later you will learn to make other functions as desired. For now, just remember that main() function is the must. Sub is the keyword to define the function name which does not return any value.

The function write is used to trace desired information. This function is inside the system.console collection. The text values must be enclosed in double quotation mark. And if you have to enter other numeric values, we don’t need to put any quotation mark.

‘ (Single quotation mark) – It is used to give comments. They are not executed in the programs. It is only the help for the programmers to understand the code.

Similary system.threading.thread.sleep(2000) holds the screen for 2seconds. i.e. 2000 milliseconds before exit.

Some basic functions

Write : This function is used to trace the desired information.

Writeline : This function is also used to trace the desired information.

The difference between write and writeline is that, writeline breaks the line after it is traced. i.e. The instructions are printed in the new line.

Examples and its functions :

System.console.writeline(“Welcome”)

This statement traces the Welcome .

System.console.writeline(“your lucky number is “ & num)

In this statement, num can be integer, decimal, double etc which are numerical data types. So it prints your lucky number is and the value of num.

System.console.readline()

The function readline is used to get the input from the user.

Num = system.console.readline()

This statement asks a value from the user which is stored in the num data type.

System.Threading.Thread.sleep(5000)

This statements holds the screen from 5 seconds.

Data types in VB.net

The basic data types supported by VB.net are:-

1. Integer

2. Double

3. Boolean – 0 and 1 i.e. 0 for false and 1 for true

4. Char – stores only a character

5. String – can store 231 unicode characters

6. Single

7. byte- data range 0 to 255

8. short

9. decimal

Variables are identifiers that are used for storing data. In VB.net variables are declared using the Dim keywords.

Some rules for defining variables:

1. A variable name mush not exceed 255 character.

2. A variable name must start with an alphabet and not a number or any other character.

3. A variable name cannot contain a period(.).

Example

Module Module1

Sub Main()

Dim name As String = "Angel" 'Store Angel to name

Dim rollno As Integer = 4 ' Store 4 to rollno

Dim sex As Char = "m" 'Store m to sex

Dim marks As Decimal = 85.25 'Store 85.25 to marks

System.Console.WriteLine("Name : " & name)

System.Console.WriteLine("Rollno : " & rollno)

System.Console.WriteLine("Sex : " & sex)

System.Console.WriteLine("Marks : " & marks)

System.Threading.Thread.Sleep(5000)

End Sub

End Module

Press F5 to see the result.

If the values of name, rollno, sex and marks are to be entered from the user then, the program can be written as:

Module Module1

Sub Main()

Dim name As String

Dim rollno As Integer

Dim sex As Char

Dim marks As Decimal

System.Console.Write("Enter name : ")

name = System.Console.ReadLine() 'Ask for the value of name

System.Console.Write("Enter Roll no. ")

rollno = System.Console.ReadLine() 'Ask for the value of roll no

System.Console.Write("Enter sex ")

sex = System.Console.ReadLine() ' Ask for the value of sex

System.Console.Write("Enter marks")

marks = System.Console.ReadLine() 'Ask for the value of marks

System.Console.WriteLine("Name : " & name)

System.Console.WriteLine("Rollno : " & rollno)

System.Console.WriteLine("Sex : " & sex)

System.Console.WriteLine("Marks : " & marks)

System.Console.Readline() 'readline at this point help in holding the ouptut until you press enter key

End Sub

End Module

If you don’t want to waste the time writing again an again the system.console then, write imports system.console at the top of the program. i.e.

Imports system.console

Module Module1

Sub Main()

Dim name As String

Dim rollno As Integer

Dim sex As Char

Dim marks As Decimal

Write("Enter name : ")

name = ReadLine() 'Ask for the value of name

Write("Enter Roll no. ")

rollno = ReadLine() 'Ask for the value of roll no

Write("Enter sex ")

sex = ReadLine() ' Ask for the value of sex

Write("Enter marks")

marks = ReadLine() 'Ask for the value of marks

WriteLine("Name : " & name)

WriteLine("Rollno : " & rollno)

WriteLine("Sex : " & sex)

WriteLine("Marks : " & marks)

readline() 'readline at this point help in holding the ouptut until you press enter key

End Sub

End Module