efa99ad275835384f42b77ff378328fc.ppt
- Количество слайдов: 75
CSCE 1030 Computer Science 1 Computer Organization and Networking 1
Components of a Computer System n Hardware n Software 2
Hardware Components – Von Neumann Architecture Secondary Storage CPU Unit © Addison Wesley 2004 3
Central Processing Unit (CPU) n A microprocessor which is an integrated circuit (IC) that performs all calculations, operations in computer n 2 components Arithmetic Logic Unit n Control Unit n 4
CPU – cont’d n ALU n Arithmetic operations (+, -, *, /) n Bitwise logic operations (AND, NOT, OR, XOR) n Shift operations n CU n Controls the flow of data through CPU n Coordinates the activities of other units 5
Control Unit (CU) n Performs the Fetch/Execute cycle: Instruction Fetch (IF) Instruction Decode (ID) Data Fecth (DF) Instruction Execution (EX) Result Return (RR) 6
Fetch/Execute Cycle Computer before executing an ADD instruction © Addison Wesley 2004 7
Fetch/Execute Cycle – cont’d Instruction Fetch © Addison Wesley 2004 8
Fetch/Execute Cycle – cont’d Instruction Decode © Addison Wesley 2004 9
Fetch/Execute Cycle – cont’d Data Fetch © Addison Wesley 2004 10
Fetch/Execute Cycle – cont’d Execute © Addison Wesley 2004 11
Fetch/Execute Cycle – cont’d Result Return © Addison Wesley 2004 12
Machine Language Instructions n Can be decoded and executed by control unit n Parts of instructions n Operation code (op code) n n Unique unsigned-integer code assigned to each machine language operation Address fields n Memory addresses of the values on which operation will work 13
Figure 5. 14 Typical Machine Language Instruction Format 14
Machine Language Instructions (continued) n Operations of machine language n Data transfer operations n n Move values to and from memory and registers Arithmetic/logic operations n Perform ALU operations that produce numeric values 15
Machine Language Instructions (continued) n Operations of machine language (continued) n Compare operations n n Compare two values and set an indicator on the basis of the results of the compare; set register bits Branch operations n Jump to a new memory address to continue processing 16
Control Unit Registers and Circuits n Parts of control unit n Links to other subsystems n Instruction decoder circuit n Two special registers n Program counter (PC) § Stores the memory address of the next instruction to be executed n Instruction register (IR) § Stores the code for the current instruction 17
Figure 5. 16 Organization of the Control Unit Registers and Circuits 18
Storage n Primary Storage (Memory) n ROM n RAM n Secondary (Auxiliary) Storage n Hard disk (HDD) n Tape n CD and DVDs n Flash disk, etc. . 19
Memory – cont’d n Read Only Memory (ROM) n Non-volatile: content is always there n Only manufacturer can write on ROM, once written the content cannot be changed n Stores the initial program that runs when the computer is powered (bootstrapping) n Many complex functions, such as translators for high-level languages, and OSes are stored in ROM 20
Memory n Random Access Memory (RAM) n Volatile – content is lost when computer is off n Provides faster access than secondary storage n Can be read and written n Is like the working memory n Memory made of addressable cells (8 bits) n All memory cells accessed in equal time n Memory address n n Unsigned binary number N long Address space is then 2 N cells 21
Figure 5. 3 Structure of Random Access Memory 22
RAM n Parts of the memory subsystem n Fetch/store controller n Fetch: Retrieve a value from memory n Store: Store a value into memory n Memory address register (MAR) n Memory data register (MDR) n Memory cells with decoder(s) to select individual cells 23
Memory and Cache (continued) n Fetch operation n The address of the desired memory cell is moved into the MAR n Fetch/store controller signals a fetch, accessing the memory cell n The value at the MAR’s location flows into the MDR 24
Memory and Cache (continued) n Store operation n The address of the cell where the value should go is placed in the MAR n The new value is placed in the MDR n Fetch/store controller signals a store, copying the MDR’s value into the desired cell 25
Memory and Cache (continued) n Memory register n Very fast memory location n Given a name, not an address n Serves some special purpose n Modern computers have dozens or hundreds of registers 26
Figure 5. 7 Overall RAM Organization 27
Cache Memory n Memory access is much slower than processing time n Faster memory is too expensive to use for all memory cells n Locality principle n Once a value is used, it is likely to be used again n Small size, fast memory just for values currently in use speeds computing time 28
Secondary Storage n Memory external to the main body of the computer n Stores large amounts of data and programs for future n n 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 29
Secondary Storage – cont’d n Mass storage devices n Direct access storage device n n n Hard drive, CD-ROM, DVD Uses its own addressing scheme to access data Sequential access storage device n Tape drive n Stores data sequentially n Used for backup storage these days 30
Secondary Storage – cont’d n Direct access storage devices n Data stored on a spinning disk n Disk divided into concentric rings (sectors) n Read/write head moves from one ring to another while disk spins n Access time depends on n Time to move head to correct sector n Time for sector to spin to data location 31
Figure 5. 8 Overall Organization of a Typical Disk 32
Peripheral Devices (Input – Output Units) n Connected to computer main body physically n Used to input and/or output data n I/O controller n Intermediary between central processor and I/O devices n Processor sends request and data, then goes on with its work n I/O controller interrupts processor when request is complete 33
Figure 5. 9 Organization of an I/O Controller 34
Software n Programs that are stored in computer n 2 types n Systems Programs n n OSes, such as Windows, Mac, Linux, Unix, etc. Application Programs n Specific programs, such as payroll program, accounting program, etc. 35
Computer Networks n A computer network is a group of interconnected computers to share resources and exchange data through a communications link n Requires two or more individual systems n something to share, e. g. printer, file n A transmission medium n A protocol, i. e. rules of communication n 36
Why do we need networks? n Distribute computation task among different computers – parallel processing n Access to remote resources n Personal communications (e-mail, live chat, audio/video conferencing) n Internet!! n etc. 37
Communication Links n Switched, dial-up telephone line n A circuit is temporarily established between the caller and callee n Analog medium n Requires modem at both ends to transmit information produced by a computer n Computer produces digital information 38
Figure 7. 1 Two Forms of Information Representation 39
Figure 7. 2 Modulation of a Carrier to Encode Binary Information 40
Communication Links (continued) n Dial-up phone links n Transmission rate: 56, 000 bps (56 Kbps) n Broadband n Transmission rate: exceeding 128, 000 bps (128 Kbps) 41
Communication Links (continued) n Options for broadband communications n Home use n n n Digital subscriber line (DSL) Cable modem Commercial and office environment n Ethernet n Fast Ethernet n Gigabit Ethernet 42
Figure 7. 3 Transmission Time of an Image at Different Transmission Speeds 43
Communication Links (continued) n Wireless data communication n Uses radio, microwave, and infrared signals n Enables “mobile computing” n Types of wireless data communication n Wireless local access network n Wireless wide-area access network 44
Local Area Networks n Local area network (LAN) n Connects hardware devices that are in close proximity n The owner of the devices is also the owner of the means of communications n Common wired LAN topologies n Bus n Ring n Star 45
Figure 7. 4 Some Common LAN Topologies 46
Figure 7. 5: An Ethernet LAN Implemented Using Shared Cables 47
Figure 7. 6 An Ethernet LAN Implemented Using a Hub 48
Wide Area Networks n Wide area networks (WANs) n Connect devices that are across town, across the country, or across the ocean n Users must purchase telecommunications services from an external provider n Dedicated point-to-point lines n Most use a store-and-forward, packet-switched technology to deliver messages 49
Figure 7. 7 Typical Structure of a Wide Area Network 50
Overall Structure of the Internet n All real-world networks, including the Internet, are a mix of LANs and WANs n Example: a company or a college n n One or more LANs connecting its local computers Individual LANs interconnected into a widearea “company network” 51
Figure 7. 8(a) Structure of a Typical Company Network 52
Overall Structure of the Internet (continued) n Internet Service Provider (ISP) n A wide-area network n Provides a pathway from a specific network to other networks, or from an individual to other networks n ISPs are hierarchical n Interconnect to each other in multiple layers to provide greater geographical coverage 53
Figure 7. 8(b) Structure of a Network Using an ISP 54
Figure 7. 8(c) Hierarchy of Internet Service Providers 55
Overall Structure of the Internet (continued) n Internet n A huge interconnected “network of networks” n Includes nodes, LANs, WANs, bridges, routers, and multiple levels of ISPs n Early 2003 n n 170 million nodes (hosts) Hundreds of thousands of separate networks located in over 225 countries 56
Communication Protocols n A protocol n A mutually agreed upon set of rules, conventions, and agreements for the efficient and orderly exchange of information n TCP/IP n The Internet protocol hierarchy n Governs the operation of the Internet n Five layers 57
Figure 7. 10 The Five-Layer TCP/IP Internet Protocol Hierarchy 58
Physical Layer n Protocols govern the exchange of binary digits across a physical communication channel n Goal: create a “bit pipe” between two computers 59
Data Link Layer n Protocols carry out n Error handling n Framing n Creates an error-free “message pipe” n Composed of two services n Layer 2 a: medium access control n Layer 2 b: logical link control 60
Data Link Layer (continued) n Medium access control protocols n Determine how to arbitrate ownership of a shared line when multiple nodes want to send at the same time n Logical link control protocols n Ensure that a message traveling across a channel from source to destination arrives correctly 61
Network Layer n Delivers a message from the site where it was created to its ultimate destination n Critical responsibilities n Creating a universal addressing scheme for all network nodes n Delivering messages between any two nodes in the network 62
Network Layer (continued) n Provides a true “network delivery service” n Messages are delivered between any two nodes in the network, regardless of where they are located n IP (Internet Protocol) layer n Network layer in the Internet 63
Transport Layer n Provides a high-quality, error-free, order preserving end-to-end delivery service n TCP (Transport Control Protocol) n Primary transport protocol on the Internet n Requires the source and destination programs to initially establish a connection 64
Figure 7. 15 Logical View of a TCP Connection 65
Application Layer n Implements the end-user services provided by a network n There are many application protocols, including: n HTTP n SMTP n POP 3 n IMAP n FTP 66
Figure 7. 16 Some Popular Application Protocols on the Internet 67
Application Layer (continued) n Uniform Resource Locator (URL) n A symbolic string that identifies a Web page n Form protocol: //host address/page n The most common Web page format is hypertext information n Accessed using the HTTP protocol 68
Network Services and Benefits n Services offered by computer networks n Electronic mail (email) n Bulletin boards n News groups n Chat rooms n Resource sharing n Physical resources n Logical resources 69
Network Services and Benefits (continued) n Services offered by computer networks n Client-server computing n Information sharing n Information utility n Electronic commerce (e-commerce) 70
A Brief History of the Internet and the World Wide Web: The Internet n August 1962: first proposal for building a computer network n Made by J. C. R. Licklider of MIT n ARPANET n Built by the Advanced Research Projects Agency (ARPA) in the 1960 s n Grew quickly during the early 1970 s 71
The Internet (continued) n NSFNet: A national network built by the National Science Foundation (NSF) n October 24, 1995: Formal acceptance of the term “Internet” n Internet service providers start offering Internet access once provided by the ARPANET and NSFNet 72
Figure 7. 20 State of Networking in the Late 1980 s 73
The World Wide Web n Development completed in May 1991 n Designed and built by Tim Berners-Lee n Components n Hypertext n n A collection of documents interconnected by pointers called links URL (Uniform Resource Locator) n The worldwide identification of a Web page located on a specific host computer 74
Figure 7. 21 Hypertext Documents 75