menu driven program in vb

Private Sub cmdClear_Click()
    Text1.Text = ""
    Text2.Text = ""
    Text3.Text = ""
    Text1.SetFocus
End Sub

Private Sub cmdExit_Click()
    Unload Me
End Sub

Private Sub mnuadd_Click()
    Text3.Text = Val(Text1.Text) + Val(Text2.Text)
End Sub

Private Sub mnuDiv_Click()
    Text3.Text = Val(Text1.Text) / Val(Text2.Text)
End Sub

Private Sub mnuMult_Click()
    Text3.Text = Val(Text1.Text) * Val(Text2.Text)
End Sub

Private Sub mnusub_Click()
    Text3.Text = Val(Text1.Text) - Val(Text2.Text)
End Sub

Output:-

INTERNET INTRANET EXTRANET

What is Internet ?
It is a Global network of computers, (servers or clients) to exchange information.
It is a "network of networks" that includes millions of  private and public, academic, business, and government networks (local or Global),
linked by copper wires, wireless connections, and other technologies.

Hardware and Software of Internet
Variety of hardware and software are used to make Internet functional.

• Modem

Device that enables computers to communicate through phone lines.
When we start internet the our modem communicates to modem of ISP.

• Computer

In addition to a modem, you need a client capable of handling multiple data types.

• Software

Two types of software’s required to enable your PC as an Internet PC.
        Communication software to establish connection
        Client software for browsing, e-mail, news.
        these software’s are provided with windows itself


Applications Of Internet :-

1. Download programs and files
2. E-Mail
3. Voice and Video Conferencing
4. E-Commerce
5. File Sharing
6. Information browsing
7. Search the web addresses for access through search engine
8. Chatting and many more…

Disadvantages of Internet:-

1. Theft of personal information such as name, address, credit card number etc.
2. Virus threats nothing but a program which disrupts the normal functioning of your system.
3. Spamming refers to receiving unwanted e-mails in bulk, which provide no purpose and needlessly obstruct the entire system.
4. Pornography This is perhaps the biggest threat related to children’s healthy mental life. A very serious issue concerning the Internet. 

Though, internet can also create havoc, destruction and its misuse can be very fatal, 

the advantages of it outweigh its disadvantages

What is Intranet ?

Internal company network that uses Internet standards (HTML, HTTP & TCP/IP protocols) & software.

Accessed only by authorized persons, especially members or employees of the organization

Intranet Security:-

Two levels of Security required:

Internal

It can be imposed by  Public Key Security & Encryption Key.

External

Through Firewall.

What is Firewall?

Security device located between firm’s internal network (intranet) & external network (internet).

Regulates access into & out of a company’s network based on a set of rules.

Note :  needs to be upgraded from time to time to check latest potential security problems.

Virtual Private Network (VPN):-

A secure connection between two points across the Internet

Tunneling:-

The process by which VPNs transfer information by encapsulating traffic in IP packets and sending the packets over the Internet

Applications of Intranet

1. Sharing of company policies/rules & regulations
2. Access employee database
3. Distribution of circulars/Office Orders
4. Access product & customer data
5. Sharing of information  of common interest
6. Launching of personal/departmental home pages
7. Submission of reports 

What is Extranet?

Extranet is an Intranet for outside authorized users using same internet technology.

Inter-organizational information system.

Enable outsiders to work together with company’s employees. 

Open to selected suppliers, customers & other business partners

Corporate telephone directories

Examples..

Dealers/distributors have access to product files such as :-

• product specification,
• pictures,
• images, etc.
• to answer the queries of the customer.

Components of extranets ..

1. Some basic infrastructure components such as the internet Including :- 
2. TCP/IP protocols,
3. E-mail,
4. Web-browsers,
5. External business partners &
6. Tele-commuting employees place order, check status & send E-mail.

Benefits of Extranet:-

1. Improved quality.
2. lower travel costs.
3. lower administrative & other overhead  costs.
4. reduction in paperwork.
5. delivery of accurate information on time.
6. improved customer service.
7. better communication.
8. overall improvement in business effectiveness.

Disadvantages of Extranet:-

1. The suppliers & customer who don’t have technical knowledge feel problem.
2. Faceless contact.
3. Information can be  misused  by other competitors.
4. Fraud may be possible.
5. Technical Employees are required.