What is the Internet? And its brief history.

THE INTERNET 

The Internet is a network of a large number of computer networks around the world. It is a data communication system. Through this system millions of computers have been linked together. The Internet consists of both the hardware and the software. The hardware comprises the computer and the connections between them. The software consists of programs that let these computers communicate with each other. More than 65,000 computer networks and 20 million computers are permanently attached to the Internet. Connections to the Internet are available in about 150 countries and 50 million people have access to it. All three major media of communication are use to connect the networks and the computers in the Internet.

(1) Telephone Lines

(2) Fiber-optic cables

(3) Satellite communications

There are generally three types of computers in the Internet. These are hosts servers and users.

• Hosts store information in the form of text pictures sound and video films.
• Servers allow users to connect to the Internet. Servers also help the to store and share information on the Internet.
• Users use information stored on the hosts and pass messages to gather computers attached to the Internet.

Who Developed the Internet?

The Government of the United States started a project in 1960s to develop an efficient system of data communication. Under this project a network of 4 computers was established in September 1969 in the United States. The idea of computer networking soon became popular. Several universities and research organizations developed their own computer networks. They joined their networks to the US Government network. The original communication network became a network of networks. This network of computer networks was called the Internet.

Who Owns the Internet?

There is no single organization or government who control the available on the Internet. Millions of people now have access to the Internet. They use it to get information play game and communication also use the Internet to advertise and sell goods.

How to connect to the Internet?

The Internet can be accessed by connecting a personal computer to the Server of an Internet Service Provider (ISP) through telephone lines. To link up an ISP following is required:

A computer

Any computer can be used but it is easier to use a computer running under Windows Operating System.

A modem

It is an electronic device that links a user computer to the Server of the ISP via telephone lines.

Dial Up Software

Dial Up Networking software establishes connection between the personal computer and the Server of the ISP. This software is built into the Windows Operating System.

Web Browser 

A browser is required for browsing or surfing the Internet.

Membership of an ISP

Membership of an ISP permits a member to connect to its Server.

THE WORLD WIDE WEB

The millions of linked documents stored on compute permanently connected to the Internet throughout the world are called the World Wide Web. It is abbreviated as www or 3w. The documents on the Web contain information in the form of texts graphics videos clips and sounds. These documents are also called Web page and are stored on computers permanently connected to the Internet. The computers containing these documents are called Web sites or sites. Each web site has a unique name called site address. Site addresses are also called domain name or URL (Universal Resource Locator). A domain name or URL is made up of two or more names separated by dots.

HOW TO CREATE A WEB PAGE

Web pages are written in hypertext. Hypertext provides several facilities that are not available in conventional text documents. A hypertext document can:

1. Show text in different founts and colors.
2. Have sounds video clips and animations.
3. Provide links to other documents on the web.

The links to other documents or pages are called hyperlinks. Hyperlinks in web pages connect all pages available on the web and make it the World Wide Web. The user can directly go to the linked page just by clicking on the hyperlink. Hypertext documents are prepared using special languages. The most popular hypertext languages include XMGL, WML and WAP.

HOW TO LOCATE A PAGE

Each web is stored on a computer permanently connected to the Internet in a file. Each file is given a unique address. It is called Universal Resource Locator or URL. URL is sometime pronounced as earl. It has particular format. http://The URL begins with the protocol. http stands for Hypertext Transfer Protocol.

SMTP Services

The SMTP Service processes incoming traffic from any SMTP host. SMTP is also used in most communications between Exchange Servers (except Exchange 5.x Servers which use RPC for message transferring). SMTP is also responsible for some advanced Exchange Server functions like Message Journaling. During the Exchange installation, the built in SMTP Service from Windows Server 2003 will be extended with several new functions. Some of the Enhancements are:

• Moving the Message Queue Directories to the Exchange installation Directory
• Providing support for the LSA (Link State Algorithm) in SMTP
• Moving SMTP Messaging from IIS to the Exchange System Manager

Message Flow

• MAPI client sends a message to a remote recipient
• Information Store (Store.exe) receives the message
• The created MailMsg object is forwarded to the Advanced Queue Engine (AQE)
• The Message Categorizer from the AQE processes the MailMsg object and splits it into MIME or RTF as necessary
• The Message Categorizer expands groups and checks defined Message limits on Exchange
• The MailMsg object is then transferred to the Remote Destination Domain within the AQE
• The AQE passes the destination address to the Exchange Routing Engine
• The AQE passes the destination address to the Exchange Routing Engine
• SMTP initiates an SMTP session with the remote SMTP host
• After the SMTP session with the remote host has been established, the information store retrieves the body of the message and converts the message as necessary
• SMTP sends the Message from the Queue to the Remote Host

The following Exchange Features require the use of SMTP:

• Intra Server Message Delivery
• Inter Server Message Delivery
• Message Delivery to the Internet
• Exchange of Routing Information

Diagnostic Logging

One other troubleshooting helper is the Diagnostic Logging of Exchange Server 2003. Diagnostic Logging sets the details that are logged in the Event Viewer for specific Exchange components to a higher level, so more information will be logged in the Event Viewer Application Log .

Diagnostic Logging should only be enabled when troubleshooting specific problems because Diagnostic Logging quickly fills the Event Log. The Logging Level can be set from None to Maximum in the GUI but there is also a Registry Key for setting the Logging Level to Level 7 for SMTP Logging purposes.

Diagnostic Logging must be enabled in the Exchange System Manager under the Exchange Server object.

After enabling the Diagnostic Logging feature the Event Viewer can be analyzed for specific problems.

How To Configure InterVLAN Routing on Layer 3 Switches?

Introduction

VLANs divide broadcast domains in a LAN environment. Whenever hosts in one VLAN need to communicate with hosts in another VLAN, the traffic must be routed between them. This is known as inter-VLAN routing. On Catalyst switches it is accomplished by creating Layer 3 interfaces (Switch virtual interfaces (SVI) ). This document provides the configuration and troubleshooting steps applicable to this capability.

Note: This document uses a Catalyst 3550 as an example. However, the concepts can also be applied to other Layer 3 switches that run Cisco IOS® (for example, Catalyst 3560, 3750, Catalyst 4500/4000 Series with Sup II+ or later, or Catalyst 6500/6000 Series that run Cisco IOS System software).

Prerequisites

Requirements

Catalyst switch models 3560, 3750, Catalyst 4500/4000 Series with Sup II+ or later, or Catalyst 6500/6000 Series that run Cisco IOS system software support basic InterVLAN routing features in all their supported software versions. Before you attempt this configuration on a 3550 series switch, ensure that you meet these prerequisites:

· InterVLAN routing on the Catalyst 3550 has certain software requirements to support interVLAN routing on the switch. See this table to determine whether your switch can support interVLAN routing.

Image Type and Version	InterVLAN Routing Capability
Enhanced Multilayer Image (EMI) - All Versions	Yes
Standard Multilayer Image (SMI) - prior to Cisco IOS Software Release12.1(11)EA1	No
Standard Multilayer Image (SMI) - Cisco IOS Software Release 12.1(11)EA1 and later	Yes

Components Used

The information in this document is based on these software and hardware versions:

· Catalyst 3550-48 that runs Cisco IOS Software Release 12.1(12c)EA1 EMI

The information presented in this document was created from devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If you are working in a live network, ensure that you understand the potential impact of any command before using it.

Conventions

For more information on document conventions, refer to the Cisco Technical Tips Conventions.

Configure InterVLAN Routing

Task

In this section, you are presented with the information to configure the features described in this document.

This logical diagram explains a simple interVLAN routing scenario. The scenario can be expanded to include a multi-switch environment by first configuring and testing inter-switch connectivity across the network before configuring the routing capability. For such a scenario that uses a Catalyst 3550, refer to Configuring InterVLAN Routing with Catalyst 3550 Series Switches.

Broadband Troubleshooting Tips

Home networks not designed and/or implemented by Honeywell GTS, are not within of the scope of the support model for iPass/Remote Access. The following tips are offered as a resource for working with your ISP or network provider to resolve any connectivity problems.

The following Ports are required to be open on your local router (wired or wireless) for iPass and CheckPoint VPN-1 SecureClient:

Port 80 for iPassConnectEngine.exe (iPass destination server IP 216.239.109.200)

TCP 443 for Visitor Mode

Protocol 50 for ESP

UDP 10000 for UDP Encapsulation

UDP 500 for IKE

TCP 500 for IKE over TCP

TCP 18231 for Policy Server logon when the client is inside the network

UDP 18233 for Keep alive protocol when the client is inside the network

TCP 18232 for Distribution Server when the client is inside the network

TCP 264 for topology downloads

UCP 259 for MEP configuration

UDP 18234 for performing tunnel test when the client is inside the network

TCP 18264 for ICA certificate registration

Ports 500 & 10,000 (both TCP and UDP) need to be opened for the VPN tunnel by the ISP. Please contact them. Make sure that your personal router has these same ports opened.  IPSEC needs to be enabled. This includes offices, hotels and homes. (Direct connect or wireless)

Cable Modem

Single Direct Connection - For stand-alone PCs that do not use routing device.

Ensure the ISP supports IPSec and is configured to allow IPSec traffic to pass 

Connect the PC directly to the cable modem 

Power up the cable modem, then the PC 

Test for Internet connectivity before launching iPass. 

See the hardware documentation for configuration details or contact the hardware vendor or ISP for additional troubleshooting recommendations. 

Sharing connection with a router (Wired or Wireless)

In general, routing devices used to network other PCs to a cable modem are the primary source of VPN connectivity problems. These devices may have the capability to act as a firewall, router and may provide Network Address Translation (NAT). 

Ensure the ISP supports IPSec and is configured to allow IPSec traffic to pass 

Bypass the router by connecting the PC directly to the cable modem 

Power up the cable modem then the PC 

Test for Internet connectivity before launching IPASS 

After successfully connecting to IPASS while bypassing the routing device, you can reconnect the PC and router in the correct manner. You may need to reboot everything.  Be sure to first start up the cable modem, then the router, then the PC.

Ensure your router supports IPSec, (sometimes referred to as IPSec pass through or VPN pass through), and it is enabled. See your hardware documentation for configuration details or contact your hardware vendor or ISP for more information. 

You may have to disable any firewall feature on your router. 

Make sure your router firmware is current. Even though the configuration looks like it supports IPSec traffic, a firmware upgrade may be necessary to get connected. Check your hardware vendor's website for the latest firmware updates and instructions to update your hardware. 

See the hardware documentation for configuration details or contact the hardware vendor or ISP for additional troubleshooting recommendations. 

DSL

DSL devices are usually routing devices as well, and are frequently the target of connectivity problems. As with cable modems, successful DSL connections require that the ISP support IPSec and be configured to allow IPSec traffic to pass. See your hardware documentation for configuration details or contact your hardware vendor or ISP for additional troubleshooting recommendations.

Recommended Wireless Routers:

LinkSys and Netgear.  Wired and wireless.

Routers known to not work with IPASS/CheckPoint Client:

DLink routers

EMEA:

Any router that connects via USB cable and shows up as a dial up device cannot be used.  We found this specifically in some of the BT Voyager modems/routers (British Telecom 105).  If it can be configured with manufacturer firmware to show up as a broadband device it should be configurable in the IPASS product.

Any AOL provided broadband solution:  (such as RoadRunner).

USA:

Any router that connects via USB cable and shows up as a dial up device cannot be used unless it truly has a dial up option. 

ADSL routers utilizing PPPOa cannot be used because they are not able to been configured as a broadband device.

Any AOL provided broadband solution:  (such as RoadRunner).

Distance Vector Routing Protocols

Most routing protocols fall into one of two classes: distance vector or link state. The basics of distance vector routing protocols are examined here; the next section covers link state routing protocols. Most distance vector algorithms are based on the work done of R. E. Bellman, L. R. Ford, and D. R. Fulkerson, and for this reason occasionally are referred to as Bellman-Ford or Ford-Fulkerson algorithms. A notable exception is EIGRP, which is based on an algorithm developed by J. J. Garcia Luna Aceves.

R. E. Bellman. Dynamic Programming. Princeton, New Jersey: Princeton University Press; 1957.

L. R. Ford Jr. and D. R. Fulkerson. Flows in Networks. Princeton, New Jersey: Princeton University Press; 1962.

The name distance vector is derived from the fact that routes are advertised as vectors of (distance, direction), where distance is defined in terms of a metric and direction is defined in terms of the next-hop router. For example, "Destination A is a distance of five hops away, in the direction of next-hop Router X." As that statement implies, each router learns routes from its neighboring routers' perspectives and then advertises the routes from its own perspective. Because each router depends on its neighbors for information, which the neighbors in turn might have learned from their neighbors, and so on, distance vector routing is sometimes facetiously referred to as "routing by rumor."

Distance vector routing protocols include the following:

• Routing Information Protocol (RIP) for IP
• Xerox Networking System's XNS RIP
• Novell's IPX RIP
• The Cisco Systems Internet Gateway Routing Protocol (IGRP) and Enhanced Internet Gateway Routing Protocol (EIGRP)
• DEC's DNA Phase IV
• AppleTalk's Routing Table Maintenance Protocol (RTMP)

Common Characteristics

A typical distance vector routing protocol uses a routing algorithm in which routers periodically send routing updates to all neighbors by broadcasting their entire route tables.

A notable exception to this convention is the Cisco Enhanced IGRP. EIGRP is a distance vector protocol, but its updates are not periodic, are not broadcasted, and do not contain the full route table. "Enhanced Interior Gateway Routing Protocol (EIGRP)."

The preceding statement contains a lot of information. Following sections consider it in more detail.

Periodic Updates

Periodic updates means that at the end of a certain time period, updates will be transmitted. This period typically ranges from 10 seconds for AppleTalk's RTMP to 90 seconds for the Cisco IGRP. At issue here is the fact that if updates are sent too frequently, congestion and router CPU overloading might occur; if updates are sent too infrequently, convergence time might be unacceptably high.

Neighbors

In the context of routers, neighbors mean routers sharing a common data link or some higher-level logical adjacency. A distance vector routing protocol sends its updates to neighboring routers and depends on them to pass the update information along to their neighbors. For this reason, distance vector routing is said to use hop-by-hop updates. This statement is not entirely true. Hosts also can listen to routing updates in some implementations; but all that is important for this discussion is how routers work.

Broadcast Updates

When a router first becomes active on a network, how does it find other routers and how does it announce its own presence? Several methods are available. The simplest is to send the updates to the broadcast address (in the case of IP, 255.255.255.255). Neighboring routers speaking the same routing protocol will hear the broadcasts and take appropriate action. Hosts and other devices uninterested in the routing updates will simply drop the packets.

Full Routing Table Updates

Most distance vector routing protocols take the very simple approach of telling their neighbors everything they know by broadcasting their entire route table, with some exceptions that are covered in following sections. Neighbors receiving these updates glean the information they need and discard everything else.

Operating System (OS)

The Operating System (OS) is an integral part of your computer. It acts as an interpreter between the different application software programs and your computer. The OS can understand the data, information and commands used by different programs because those programs are written or coded specifically for that Operating System's interface, using it's standard rules, commands and protocols. It then translates the many commands and information into procedures the computer can understand. Computers are not of much use without an operating system.

Just a quick note on Operating Systems. As I said before, your computer will not work without one. The accepted practice in most stores is to sell computers with operating systems.

Recently, I was buying a computer for a customer and one particular store had prices considerably lower than others. Of course, there were the usual price cutting features, smaller hard drive, cheaper video card, less RAM, etc..., but it would serve the purpose. They offered the choice of Windows98 or 2000, which was really nice of them... considering the fact that you had to buy it off the shelf!

If you wanted an Operating System with your computer, it was going to cost you extra!
Make sure of what you're getting

Tips & Tricks

Tips & Tricks can often be an interesting, fun and fast way of learning a particular software. As far as understanding the computer and its operating system, everybody is at a different level. And everyone is always learning. There's so many different ways of performing the same function in a single operating system that its impossible to know them all. The OS has become so huge and intricate that even a person considered an expert couldn't possibly be aware of all the capabilities of today's Operating Systems (let alone the thousands of applications out there).

Many of the Tips & Tricks presented on this Site may be fairly basic, but as I said before, everyone is at a different level. Other tips may not be so common. I'll continue to add them when I have time or as they come up.

The Tips & Tricks found on this site are gathered from experience, magazine articles, e-zincs, other websites and reader submission. If you have a favorite that you'd like to share with other readers, please send it to us.

What is a Network?

Modern networks have more than the physical and the data link layers. The network layer is a set of mechanisms that can be used to send packets from one computer to another in the world. There are two types of networks: With packet switching, data packets can be carried together on the same link. They are differentiated by addressing information. Packet switching is the basis for all data networks today, including the Internet, public data networks such as Frame Relay or X.25, and even ATM. Packet switches have queues. Circuit switching is the way telephone networks operate. A circuit emulates the physical signals of a direct end-to-end cable. When computers are connected by a circuit switched network, they establish a direct data link over the circuit. This is used today for modem access to a data network. Modern circuit switches are based on byte multiplexing and are thus similar to packet switches, with the main difference that they perform non-statistical multiplexing.

A network has intermediate systems (ISs): those are systems that send data to next ISs or to the destination. Using interconnected ISs saves cable and bandwidth. Intermediate systems are known under various terms depending on the context: routers (TCP/IP, AppleTalk,…), switches (X.25, Frame Relay, ATM, telephone), communication controllers (SNA), network nodes (APPN)

WHAT IS PASSWORD ?

What is a password? Give examples:

PASSWORD

A password is a secret word, a number or a combination of the two that must be type on the keyboard to set access to the computer system. In a computer a password is applied to limit the use of a computer system or software. Only those persons who know the password can use the system. These are called the persons authorized to use the system. A password protected system or software asks for the password before its execution. If the person is authorized to use the system and knows the password, he types it. The system of software confirms the password and its executions starts if correct password is entered. Otherwise the system or software dose not execute. The authorized persons can change passwords. The authorized persons must keep their password secret. They should not forget their passwords. While adopting a password for a system or software the following points must be in mind:

             

• The password should not be a commonly used word.

• The password must be a combination of alphabetic letters and numeric digits.

• The password should be written down in a notebook because if it is forgotten the system cannot be run.

• Password should be changed at least once a month.

Examples of Password Protection:

(1)         Different computers have different set-up of configurations i.e. the arrangement of their parts of their parts. These configurations are given in the set-up of the computers. The computer set-up is usually accessed pressing Del key after starting the computer. The user of the computer sets the configurations according to his needs and protect them with a password. Only the person who make changes in it. Thus the computer set-up is protected from being change by unauthorized persons. The authorized persons can however also change the password.

(2)  When one gets the memberships of an Internet Service Provider (ISP), he or she Is given a user name and a password. The user name is usually the name of the person and the password is the secret code that he uses to access the ISP. While the user name of the person remains the same the password can be changed. All ISPs give a procedure for changing it.

BACKUP OF DATA ?

What is meant by backup of data? Why is it necessary to make a backup copy of your data?

BACKUP OF DATA

The copy of data or information stored in the computer hard disk or on another storage media for example floppy disk Zip disk or CD ROM is called the backup of data. The hard disk of the computer is usually used for storage of data. It is generally a reliable storage device. But it can develop problems due to voltage fluctuations or other reasons. If a hard disk is damaged all data on it cannot be retrieved. Thus the data may be lost. In such a situation the data stored as backup can be retrieved and stored on the new hard disk. This can save the time and the effort of creating data new. The computer on which data is kept may   be stolen or a fire in the room may damage it. In these circumstances the backup of the data is used. It is necessary that the backup of the data be prepared regularly and placed at a fire proof and safe place. In large organizations the backup is normally kept on the floppy disks or Zip disks or Write-able CD-ROMS. These are two manners in which backup are created. These are complete backup and incremental backups.

COMPLETE BACKUP

A complete backup means a backup of all data stored on the computer hard disk.

Advantage of Complete Backup

A copy of the entire hard disk is created. The entire data can be restored if it is damaged.

Disadvantage of Complete Backup

It takes much time to create backup of entire hard disk. Each time backup is created the entire data is copied.; It takes longer time to create the backup.

INCREMENTAL BACKUP

An incremental Backup means the weekly backup of the entire data. At the end of the day backup of only new files and those files that are changed since last backup is made. It takes less time to make backup since a backup of only a small number of files is created each day.

 

COMPUTER VIRUS?

A computer virus is a small program that interferes with normal functions the computer. Usually a virus program is attached to a computer file. The file to which a virus is attached file is copied a disk, the virus is also copied and it hides itself on the disk.

Activation of a Virus

The running of a virus program residing in a computer is called activation of the virus. The virus program executes when it is activated. The method of activation of a computer virus is defined in the virus program itself. Different computer viruses are activated in different ways. For example, Some viruses activate on a fixed date. Usually these viruses are part of some application software. When the application software is run on the computer it checks the system date. If the system date matches the virus program date the virus is activated. For example Friday the 13^th virus activates only if the date is 13^th and the day is Friday.

How Computer Gets a Virus

• Transfer of a virus program into the hard disk of a computer is called infecting of the computer with a virus. There are many ways through which a computer can get a virus. Most common ways are: Nowadays the most common way of transfer of virus to a computer is through the Internet. For example
• A virus can be attached to an e-mail message. When this e-mail message carrying the virus is download onto a computer the virus is also downloaded.
• A virus can also be attached to some software on the Internet. When this software is downloaded from the Internet into your computer the virus is also transferred. When a virus-affected file is copied from one computer to another through a floppy disk the virus is also transferred.

Action of a Virus

Different computer viruses create different problems in different ways. The most common problems are:

·         A virus may destroy all data stored in the hard disk by either formatting it without warning or by destroying some of its sectors.

·         A virus may change the boot sector of the hard disk if the boot sector of a disk is a affected it cannot boot the computer.

·         The computer viruses are automatically loaded into the main memory of the computer and remain in the memory. This slows down the data accessing speed of the computer.

·         A virus can destroy BIOS of the computer.

What is Magnetic Memory?

MAGNETIC MEMORY

Magnetic memory is also called secondary storage. It is used to store computer instructions and data permanently. The instructions and data stored on the magnetic memory are not lost when the computer is on the magnetic memory. Magnetic memory consists of a magnetic medium on which information is stored. Most common medium used for magnetic memory is disk. This is why magnetic memory is also called Disk Memory. There are two most common type of magnetic memories. These are floppy disks and hard disks. The magnetic memory has large capacity as compared to RAM. The reading and writing of data on magnetic is however much slower than in the RAM. Magnetic memory is used to store instructions and data permanently. When instructions are to be executed these are loaded from the magnetic memory into the RAM.

What is a computer Bus? Explain important types of buses.

COMPUTER BUSES

The electrical paths through which data is transferred from one component to another within the computer system are called computer buses. These buses connect different devices with the CPU. A bus consists of a set parallel electrical paths, usually copper tracings on the surface of the motherboard. The amount of data that a bus can carry at one time is called bus width. Bus width is measured in terms of how many bits can be carried at one time. Nowadays Intel Pentium microprocessors have 64-bit data buses. The greater the width of the computer bus, the more data it can transfer. Thus a larger bus width in a computer means a faster and more powerful computer. A computer system has several types of buses. Important buses are-discussed below:

DATA BUS

The data bus connects different parts of the computer. It is used to transfer data from one device to another.

ADDRESS BUS

The bus that is used to locate a storage position in the computer memory is called address bus. It used to locate the address of data in memory. It is also used locate the memory address of instructions to be executed.

CONTROL BUS

It is used to transfer control from one instruction to another during program execution. It also transfer control signals to different devices.

EXPANSION BUS

The bus that carries data to and from expansion on the motherboard is called expansion bus. Additional card for example, network cards, modems, sound cards are added to the expansion slots. The expansion buses connect these cards to the computer system.

What is the function of computer clock?

COMPUTER CLOCK

The computer clock is an electronic circuit that generates pulses at a rapid pace. It generates millions of pulses in one second. The pulses are reported as millions of cycles per second or Mega Hertz (MHz). The rate of generation of pulses is called the clock speed. Each pulse of the computer clock carries out one event inside the computer. Usually 1 to 6 clock pulses are required to perform one instruction. Clock speed in modem microcomputers generally varies from 100MHz to 1000 MHz. Because of this high clock speed the computer can execute millions of instruction in one second.

How the control unit executes program instructions?

EXECUTION OF INSTRUCTION  

Control Unit controls the operations of all parts of the computer system. It executes the instructions given to the computer. Execution of an instruction by the control Unit consists of four simple steps. These steps are:

(1)Instruction Fetch

It gets a program instruction stored in the main memory of the computer. This is called fetching instruction.

(2)Interpret Instruction

It decodes the instruction to find out what action is to be taken.

(3)Data Fetch

If an decoding requires certain data to operate upon, the CU fetches the data from the computer memory and loads it into a register.

(4)Execute Instruction

After decoding the instruction and getting required data the CU instruction the ALU to process the data according to the given instruction.

What is an instruction set of the CPU

TYPES OF INSTRUCTION EXECTED BY CPU

The instruction set of the CPU generally consists of four types of instructions. These are:

(1)Arithmetic Instructions

(2)Logical Instructions

(3)Data Transfer Instructions

(4)Control Transfer Instructions

Arithmetic Instructions

The instructions that are used to perform arithmetic operations of addition, subtraction, multiplication and division are called arithmetic instructions. These instructions are executed by arithmetic section of  ALU.

Logical Instructions

The instruction that are used to compare two data items with each are called logical instruction. These instruction are executed by logical section of ALU.

Data Transfer Instructions

The instructions that are used to transfer data from one unit to another during program execution are called data transfer instructions. For example, these instructions are used to transfer data from the RAM to the CPU registers.

Control Transfer Instructions

The instruction that are used to transfer the execution control from one part of the program to another during program execution are called control instructions.

How is Performance of CPU Measured

PERFORMANCE OF CPU

The performance a CPU is measured in terms of its data processing speed. Data processing speed of CPU depends upon the following three factors.

(1)Register Size

A large size register can hold larger amount of data. It increases the processing and accessing speed of CPU.

(2)Instruction Set Size

Every processor can execute a fixed set instruction for arithmetic and logical operations. It is called the instruction set of the CPU. Different CPUs have different instruction sets. Usually a modern CPUs instruction set consists of 80 to 120 instructions. Larger instruction set of CPU increases data processing speed.

(3)Clock Speed

Processing speed of the CPU depends upon the clock speed of the computer. Usually 1 to 6 ticks of the clock are required to perform one instruction. Clock speed usually varies from 100  MHz to 1000 MHz. Higher clock speed means faster data processing by the CPU.

ADVANCED FEATURES

Modern CPUs have certain advanced features that increase their data processing speed. These features are:

(1)Cache Memory

A cache (pronounced as cash) is a small very memory within the CPU. It is for speeding up the internal data transfer.

(2)Math Coprocessor

Math coprocessor is a special circuitry specially designed to perform larger and complex mathematical calculations. These are used to increase the performance of the CPU while running application program that need complicated computations. Until recently math coprocessors were used as separate chips that could be added to the computer system. Nowadays these are built within the CPU.

(3)Stack Register & Stack Management Instruction

A stack is a set of blocks of memory location where a series of data is stored one upon the other. The data cannot be stored and retrieved randomly. It is stored and retrieved in some order. The data stored in the last position is retrieved first. This method of storing and retrieving data is called Last In First Out (LIFO).