1 csce 1030 computer science 1 computer organization and networking

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CSCE 1030

Computer Science 1

Computer Organization and Networking

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Components of a Computer System

Hardware Software

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Hardware Components – Von Neumann Architecture

CPU

Unit

© Addison Wesley 2004

Secondary Storage

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Central Processing Unit (CPU)

A microprocessor which is an integrated circuit (IC) that performs all calculations, operations in computer

2 components Arithmetic Logic Unit Control Unit

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CPU – cont’d

ALU Arithmetic operations (+, -, *, /) Bitwise logic operations (AND, NOT, OR,

XOR) Shift operations

CU Controls the flow of data through CPU Coordinates the activities of other units

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Control Unit (CU)

Performs the Fetch/Execute cycle:

Instruction Fetch (IF)

Instruction Decode (ID)

Data Fecth (DF)

Instruction Execution (EX)

Result Return (RR)

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Fetch/Execute Cycle

Computer before executing an ADD instruction


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Fetch/Execute Cycle – cont’d

Instruction Fetch


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Instruction Decode


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Data Fetch


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Execute


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Result Return


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Machine Language Instructions

Can be decoded and executed by control unit

Parts of instructions

Operation code (op code)

Unique unsigned-integer code assigned to each machine language operation

Address fields

Memory addresses of the values on which operation will work

Invitation to Computer Science, Java Version, Second Edition

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Figure 5.14

Typical Machine Language Instruction Format


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Machine Language Instructions (continued)

Operations of machine language

Data transfer operations

Move values to and from memory and registers

Arithmetic/logic operations

Perform ALU operations that produce numeric values


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Machine Language Instructions (continued)

Operations of machine language (continued)

Compare operations

Compare two values and set an indicator on the basis of the results of the compare; set register bits

Branch operations

Jump to a new memory address to continue processing


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Control Unit Registers and Circuits

Parts of control unit

Links to other subsystems

Instruction decoder circuit

Two special registers Program counter (PC)

Stores the memory address of the next instruction to be executed

Instruction register (IR) Stores the code for the current instruction


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Figure 5.16

Organization of the Control Unit Registers and Circuits


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Storage

Primary Storage (Memory) ROM RAM

Secondary (Auxiliary) Storage Hard disk (HDD) Tape CD and DVDs Flash disk, etc..

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Memory – cont’d

Read Only Memory (ROM) Non-volatile: content is always there Only manufacturer can write on ROM, once

written the content cannot be changed Stores the initial program that runs when the

computer is powered (bootstrapping) Many complex functions, such as translators

for high-level languages, and OSes are stored in ROM

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Memory

Random Access Memory (RAM) Volatile – content is lost when computer is off Provides faster access than secondary storage Can be read and written Is like the working memory Memory made of addressable cells (8 bits) All memory cells accessed in equal time Memory address

Unsigned binary number N long Address space is then 2N cells

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Figure 5.3

Structure of Random Access Memory


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RAM

Parts of the memory subsystem

Fetch/store controller

Fetch: Retrieve a value from memory

Store: Store a value into memory

Memory address register (MAR)

Memory data register (MDR)

Memory cells with decoder(s) to select individual cells

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Memory and Cache (continued)

Fetch operation

The address of the desired memory cell is moved into the MAR

Fetch/store controller signals a fetch, accessing the memory cell

The value at the MAR’s location flows into the MDR

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Store operation

The address of the cell where the value should go is placed in the MAR

The new value is placed in the MDR

Fetch/store controller signals a store, copying the MDR’s value into the desired cell


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Memory register

Very fast memory location

Given a name, not an address

Serves some special purpose

Modern computers have dozens or hundreds of registers


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Figure 5.7Overall RAM Organization


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Cache Memory

Memory access is much slower than processing time

Faster memory is too expensive to use for all memory cells

Locality principle

Once a value is used, it is likely to be used again

Small size, fast memory just for values currently in use speeds computing time


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Secondary Storage

Memory external to the main body of the computer Stores large amounts of data and programs for future

use For execution, the data and programs are read into

primary storage. Non-volatile: Content does remains when the power

is turned off. Cheap and larger in capacity as compared to RAM Also called mass storage

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Secondary Storage – cont’d

Mass storage devices Direct access storage device

Hard drive, CD-ROM, DVD Uses its own addressing scheme to access

data

Sequential access storage device Tape drive Stores data sequentially Used for backup storage these days


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Secondary Storage – cont’d

Direct access storage devices Data stored on a spinning disk Disk divided into concentric rings (sectors) Read/write head moves from one ring to

another while disk spins Access time depends on

Time to move head to correct sector Time for sector to spin to data location


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Figure 5.8

Overall Organization of a Typical Disk


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Peripheral Devices (Input – Output Units) Connected to computer main body physically Used to input and/or output data I/O controller

Intermediary between central processor and I/O devices

Processor sends request and data, then goes on with its work

I/O controller interrupts processor when request is complete


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Figure 5.9

Organization of an I/O Controller


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Software

Programs that are stored in computer 2 types

Systems Programs OSes, such as Windows, Mac, Linux, Unix, etc.

Application Programs Specific programs, such as payroll program,

accounting program, etc.

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Computer Networks

A computer network is a group of interconnected computers to share resources and exchange data through a communications link

Requires two or more individual systems something to share, e.g. printer, file A transmission medium A protocol, i.e. rules of communication

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Why do we need networks?

Distribute computation task among different computers – parallel processing

Access to remote resources Personal communications (e-mail, live chat,

audio/video conferencing) Internet!! etc.

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Communication Links

Switched, dial-up telephone line

A circuit is temporarily established between the caller and callee

Analog medium

Requires modem at both ends to transmit information produced by a computer

Computer produces digital information

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Figure 7.1 Two Forms of Information Representation


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Figure 7.2

Modulation of a Carrier to Encode Binary Information


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Communication Links (continued)

Dial-up phone links

Transmission rate: 56,000 bps (56 Kbps)

Broadband

Transmission rate: exceeding 128,000 bps (128 Kbps)


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Options for broadband communications

Home use

Digital subscriber line (DSL)

Cable modem

Commercial and office environment

Ethernet

Fast Ethernet

Gigabit Ethernet


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Figure 7.3

Transmission Time of an Image at Different Transmission Speeds


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Wireless data communication

Uses radio, microwave, and infrared signals

Enables “mobile computing”

Types of wireless data communication

Wireless local access network

Wireless wide-area access network


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Local Area Networks

Local area network (LAN)

Connects hardware devices that are in close proximity

The owner of the devices is also the owner of the means of communications

Common wired LAN topologies Bus

Ring

Star


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Figure 7.4

Some Common LAN Topologies


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Figure 7.5: An Ethernet LAN ImplementedUsing Shared Cables


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Figure 7.6

An Ethernet LAN Implemented Using a Hub


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Wide Area Networks

Wide area networks (WANs)

Connect devices that are across town, across the country, or across the ocean

Users must purchase telecommunications services from an external provider

Dedicated point-to-point lines

Most use a store-and-forward, packet-switched technology to deliver messages


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Figure 7.7

Typical Structure of a Wide Area Network


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Overall Structure of the Internet

All real-world networks, including the Internet, are a mix of LANs and WANs

Example: a company or a college

One or more LANs connecting its local computers

Individual LANs interconnected into a wide-area “company network”


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Figure 7.8(a)

Structure of a Typical Company Network


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Overall Structure of the Internet (continued)

Internet Service Provider (ISP)

A wide-area network

Provides a pathway from a specific network to other networks, or from an individual to other networks

ISPs are hierarchical

Interconnect to each other in multiple layers to provide greater geographical coverage


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Figure 7.8(b)

Structure of a Network Using an ISP


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Figure 7.8(c)Hierarchy of Internet Service Providers


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Overall Structure of the Internet (continued)

Internet

A huge interconnected “network of networks”

Includes nodes, LANs, WANs, bridges, routers, and multiple levels of ISPs

Early 2003 170 million nodes (hosts)

Hundreds of thousands of separate networks located in over 225 countries


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Communication Protocols

A protocol

A mutually agreed upon set of rules, conventions, and agreements for the efficient and orderly exchange of information

TCP/IP

The Internet protocol hierarchy

Governs the operation of the Internet

Five layers


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Figure 7.10

The Five-Layer TCP/IP Internet Protocol Hierarchy


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Physical Layer

Protocols govern the exchange of binary digits across a physical communication channel

Goal: create a “bit pipe” between two computers


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Data Link Layer

Protocols carry out

Error handling

Framing

Creates an error-free “message pipe”

Composed of two services

Layer 2a: medium access control

Layer 2b: logical link control


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Data Link Layer (continued)

Medium access control protocols

Determine how to arbitrate ownership of a shared line when multiple nodes want to send at the same time

Logical link control protocols

Ensure that a message traveling across a channel from source to destination arrives correctly


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Network Layer

Delivers a message from the site where it was created to its ultimate destination

Critical responsibilities

Creating a universal addressing scheme for all network nodes

Delivering messages between any two nodes in the network


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Network Layer (continued)

Provides a true “network delivery service”

Messages are delivered between any two nodes in the network, regardless of where they are located

IP (Internet Protocol) layer

Network layer in the Internet


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Transport Layer

Provides a high-quality, error-free, order preserving end-to-end delivery service

TCP (Transport Control Protocol)

Primary transport protocol on the Internet

Requires the source and destination programs to initially establish a connection


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Figure 7.15

Logical View of a TCP Connection


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Application Layer

Implements the end-user services provided by a network

There are many application protocols, including:

HTTP

SMTP

POP3

IMAP

FTP


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Figure 7.16

Some Popular Application Protocols on the Internet


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Application Layer (continued)

Uniform Resource Locator (URL)

A symbolic string that identifies a Web page

Form

protocol://host address/page

The most common Web page format is hypertext information

Accessed using the HTTP protocol


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Network Services and Benefits

Services offered by computer networks

Electronic mail (email)

Bulletin boards

News groups

Chat rooms

Resource sharing Physical resources

Logical resources


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Network Services and Benefits (continued)

Services offered by computer networks

Client-server computing

Information sharing

Information utility

Electronic commerce (e-commerce)


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A Brief History of the Internet and the World Wide Web: The Internet

August 1962: first proposal for building a computer network

Made by J. C. R. Licklider of MIT

ARPANET

Built by the Advanced Research Projects Agency (ARPA) in the 1960s

Grew quickly during the early 1970s


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The Internet (continued)

NSFNet: A national network built by the National Science Foundation (NSF)

October 24, 1995: Formal acceptance of the term “Internet”

Internet service providers start offering Internet access once provided by the ARPANET and NSFNet


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Figure 7.20State of Networking in the Late 1980s


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The World Wide Web Development completed in May 1991

Designed and built by Tim Berners-Lee

Components

Hypertext A collection of documents interconnected by

pointers called links

URL (Uniform Resource Locator) The worldwide identification of a Web page

located on a specific host computer


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Figure 7.21

Hypertext Documents
