1 CSCE 1030 Computer Science 1 Computer Organization and Networking

2 Components of a Computer System Hardware Software

3 Hardware Components – Von Neumann Architecture CPU Unit © Addison Wesley 2004 Secondary Storage

4 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

5 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

6 Control Unit (CU) Performs the Fetch/Execute cycle: Instruction Fetch (IF) Instruction Decode (ID) Data Fecth (DF) Instruction Execution (EX) Result Return (RR)

7 Fetch/Execute Cycle Computer before executing an ADD instruction © Addison Wesley 2004

8 Fetch/Execute Cycle – cont’d Instruction Fetch © Addison Wesley 2004

9 Fetch/Execute Cycle – cont’d Instruction Decode © Addison Wesley 2004

10 Fetch/Execute Cycle – cont’d Data Fetch © Addison Wesley 2004

11 Fetch/Execute Cycle – cont’d Execute © Addison Wesley 2004

12 Fetch/Execute Cycle – cont’d Result Return © Addison Wesley 2004

13 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

14 Figure 5.14 Typical Machine Language Instruction Format Invitation to Computer Science, Java Version, Second Edition

15 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 Invitation to Computer Science, Java Version, Second Edition

16 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 Invitation to Computer Science, Java Version, Second Edition

17 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 Invitation to Computer Science, Java Version, Second Edition

18 Figure 5.16 Organization of the Control Unit Registers and Circuits Invitation to Computer Science, Java Version, Second Edition

19 Storage Primary Storage (Memory) ROM RAM Secondary (Auxiliary) Storage Hard disk (HDD) Tape CD and DVDs Flash disk, etc..

20 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

21 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 2 N cells

22 Figure 5.3 Structure of Random Access Memory Invitation to Computer Science, Java Version, Second Edition

23 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

24 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

25 Memory and Cache (continued) 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 Invitation to Computer Science, Java Version, Second Edition

26 Memory and Cache (continued) Memory register Very fast memory location Given a name, not an address Serves some special purpose Modern computers have dozens or hundreds of registers Invitation to Computer Science, Java Version, Second Edition

27 Figure 5.7 Overall RAM Organization Invitation to Computer Science, Java Version, Second Edition

28 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 Invitation to Computer Science, Java Version, Second Edition

29 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

30 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 Invitation to Computer Science, Java Version, Second Edition

31 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 Invitation to Computer Science, Java Version, Second Edition

32 Figure 5.8 Overall Organization of a Typical Disk Invitation to Computer Science, Java Version, Second Edition

33 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 Invitation to Computer Science, Java Version, Second Edition

34 Figure 5.9 Organization of an I/O Controller Invitation to Computer Science, Java Version, Second Edition

35 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.

36 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

37 Why do we need networks? Distribute computation task among different computers – parallel processing Access to remote resources Personal communications ( , live chat, audio/video conferencing) Internet!! etc.

38 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

39 Figure 7.1 Two Forms of Information Representation Invitation to Computer Science, Java Version, Second Edition

40 Figure 7.2 Modulation of a Carrier to Encode Binary Information Invitation to Computer Science, Java Version, Second Edition

41 Communication Links (continued) Dial-up phone links Transmission rate: 56,000 bps (56 Kbps) Broadband Transmission rate: exceeding 128,000 bps (128 Kbps) Invitation to Computer Science, Java Version, Second Edition

42 Communication Links (continued) Options for broadband communications Home use Digital subscriber line (DSL) Cable modem Commercial and office environment Ethernet Fast Ethernet Gigabit Ethernet Invitation to Computer Science, Java Version, Second Edition

43 Figure 7.3 Transmission Time of an Image at Different Transmission Speeds Invitation to Computer Science, Java Version, Second Edition

44 Communication Links (continued) 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 Invitation to Computer Science, Java Version, Second Edition

45 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 Invitation to Computer Science, Java Version, Second Edition

46 Figure 7.4 Some Common LAN Topologies Invitation to Computer Science, Java Version, Second Edition

47 Figure 7.5: An Ethernet LAN Implemented Using Shared Cables Invitation to Computer Science, Java Version, Second Edition

48 Figure 7.6 An Ethernet LAN Implemented Using a Hub Invitation to Computer Science, Java Version, Second Edition

49 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 Invitation to Computer Science, Java Version, Second Edition

50 Figure 7.7 Typical Structure of a Wide Area Network Invitation to Computer Science, Java Version, Second Edition

51 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” Invitation to Computer Science, Java Version, Second Edition

52 Figure 7.8(a) Structure of a Typical Company Network Invitation to Computer Science, Java Version, Second Edition

53 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 Invitation to Computer Science, Java Version, Second Edition

54 Figure 7.8(b) Structure of a Network Using an ISP Invitation to Computer Science, Java Version, Second Edition

55 Figure 7.8(c) Hierarchy of Internet Service Providers Invitation to Computer Science, Java Version, Second Edition

56 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 million nodes (hosts) Hundreds of thousands of separate networks located in over 225 countries Invitation to Computer Science, Java Version, Second Edition

57 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 Invitation to Computer Science, Java Version, Second Edition

58 Figure 7.10 The Five-Layer TCP/IP Internet Protocol Hierarchy Invitation to Computer Science, Java Version, Second Edition

59 Physical Layer Protocols govern the exchange of binary digits across a physical communication channel Goal: create a “bit pipe” between two computers Invitation to Computer Science, Java Version, Second Edition

60 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 Invitation to Computer Science, Java Version, Second Edition

61 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 Invitation to Computer Science, Java Version, Second Edition

62 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 Invitation to Computer Science, Java Version, Second Edition

63 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 Invitation to Computer Science, Java Version, Second Edition

64 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 Invitation to Computer Science, Java Version, Second Edition

65 Figure 7.15 Logical View of a TCP Connection Invitation to Computer Science, Java Version, Second Edition

66 Application Layer Implements the end-user services provided by a network There are many application protocols, including: HTTP SMTP POP3 IMAP FTP Invitation to Computer Science, Java Version, Second Edition

67 Figure 7.16 Some Popular Application Protocols on the Internet Invitation to Computer Science, Java Version, Second Edition

68 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 Invitation to Computer Science, Java Version, Second Edition

69 Network Services and Benefits Services offered by computer networks Electronic mail ( ) Bulletin boards News groups Chat rooms Resource sharing Physical resources Logical resources Invitation to Computer Science, Java Version, Second Edition

70 Network Services and Benefits (continued) Services offered by computer networks Client-server computing Information sharing Information utility Electronic commerce (e-commerce) Invitation to Computer Science, Java Version, Second Edition

71 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 Invitation to Computer Science, Java Version, Second Edition

72 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 Invitation to Computer Science, Java Version, Second Edition

73 Figure 7.20 State of Networking in the Late 1980s Invitation to Computer Science, Java Version, Second Edition

74 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 Invitation to Computer Science, Java Version, Second Edition

75 Figure 7.21 Hypertext Documents Invitation to Computer Science, Java Version, Second Edition