Understanding Digital Data Representation and Computer Systems - Prof. Willis Boughton, Study notes of Computer Science

Download Understanding Digital Data Representation and Computer Systems - Prof. Willis Boughton and more Study notes Computer Science in PDF only on Docsity! Chapter 2 The System Unit: Processing and Memory In order to be understood by a computer, data and programs need to be represented appropriately Coding systems (or coding schemes): represent data and programs Digital computers: devices that can only understand two states, off and on, represented by the digits 0 and 1 (bits, from binary digits) Digital data representation: process of representing data in digital form so it can be used by a computer Computers represent programs and data through binary-based coding schemes 2 Decimal Binary 0 0 1 1 2 10 3 11 4 100 5 101 6 110 7 111 8 1000 9 1001 10 1010 11 1011 12 1100 13 1101 14 1110 15 1111 16 10000 5 Number Systems DECIMAL NUMBERING SYSTEM Each place value in a decimal number represents 10 taken to the appropriate power. BINARY NUMBERING SYSTEM Each place value in a binary number represents 2 taken to the appropriate power. The decimal number 7216 The binary number 1001 —— | OL > Decimal 10 taken to =a different powers means 6 x1 means 1 x 10 means 2 x 100 € 1c 200 means 7 x 1,000 = 7,000 7 2 taken to Gen iierent powers means 1 x1 means 0 x 2 means 0 x 4 means 1x8 Glaco- equivalent 216 Convert letters into binary numbers and vice versa ASCII and EBCDIC (pp 58) ASCII (American Standard Code for Information Interchange): coding system used with PCs EBCDIC (Extended Binary-Coded Decimal Interchange Code): developed by IBM, primarily for mainframe use Unicode: newer code (32 bits per character is common); universal coding standard that represents text data written in any language 7 Is the main case of a computer Houses the processing hardware for that computer, as well as disk drives, memory, the power supply, cooling fans, etc. For a desktop PC often looks like a rectangular box For a notebook is the notebook case itself 10 System Unit, Cont'd EXPANSION CARD Used to connect peripheral devices or add new capabilities to acomputer system. EXPANSION SLOTS. Connect expansion cards to the mother- board to add addi- tional capabilities. MOTHERBOARD Connects all compo- nents of the computer system; the PC’s main circuit board. MEMORY (RAM) MODULES —— Store data temporarily while you are working with it. CPU POWER SUPPLY FAN HARD DRIVE Converts standard Cools the CPU and Stores data and programs; other important the principal storage device needed for processing, and a form the computer components. for most PCs. Performs the calculations and does the comparisons electrical power into controls the other parts of can use. the computer system. \ MEMORY SLOTS Connect memory modules to the motherboard. STORAGE BAYS Hold storage devices, such as the floppy, DVD, and hard drives shown here. DVD DRIVE Accesses data stored on CDs or DVDs. FLOPPY DRIVE Accesses data stored on floppy disks, 1 Circuit board: thin board containing chips very small pieces of silicon or other semi-conducting material onto which integrated circuits are embedded and other electronic components Motherboard or system board: the main circuit board inside the system unit External devices (monitors, keyboards, mice, printers) connect to the motherboard by plugging into a port exposed through the exterior of the system unit 12 Cache memory: very fast memory chips located on or close to the CPU Used to speed up the CPU Level 1 is fastest, followed by Level 2 More cache memory typically = faster processing Bus width and bus speed: Bus = an electronic path over which data can travel Computer uses many different buses Bus width = the number of bits the bus can transport at each clock tick The larger the bus width, the faster the bus 15 RAM (random access memory): the main, working memory of the computer Where data and instructions are put temporarily while being used Random means every byte can be accessed directly Can be read and written by CPU Consists of chips on a module plugged into the motherboard Is volatile; contents are lost when computer is shut off 16 Registers: highest-speed memory built into the CPU and used by the CPU for processing ROM (read-only memory): nonvolatile memory that stores data and programs permanently CPU can only read, not write to Set up by computer's manufacturer Contains Basic Input/Output System (BIOS), the instructions the CPU executes during system boot Flash memory: nonvolatile for data and programs CPU can read and write - contents not permanent Some is on motherboard; also on memory sticks, etc. Significantly slower than RAM 17 Expansion slot: a location on the motherboard into which expansion cards are inserted The more slots available, the more devices you can add to your computer Expansion card: a circuit board inserted into an expansion slot on a PC s motherboard to add additional functionality or to attach a peripheral device Also called add-in boards, interface cards, and adapter boards 20 Expansion Slots and Cards, Cont'd The port on this . network card is @ ‘ This part of the card plugs See into an empty expansion " slot on the motherboard. system unit’s case. COMMON EXPANSION CARDS Per MMT Accelerator board Disk controller card Modem card Network interface card Sound card TV tuner card USB or FireWire card Video capture board Video graphics board atin Uses specialized processor chips that speed up overall processing. Enables a particular type of disk drive to interface with the PC. Provides communications capabilities to connect to a network or the Internet. Enables a PC to connect to a network. Enables users to attach speakers to aPC and provides sound capabilities. Allows a PC to pick up television signals. Adds one or both of these ports to the PC. Allows video images to be input into the computer from a video camera. Enables the connection of a monitor; may provide additional graphics capabilities. 21 System bus: the bus that connects the CPU and RAM Expansion buses: connect the CPU to peripheral (typically input and output) devices Bus speed (throughput) measured in MB per second, MBps Depends on bus width and bus clock Each bus has a clock whose rate is in MHz or GHz Big difference in bus speeds; some relatively slow and some very fast 22 Connector on the exterior of system unit into which a device can be attached Most on back of system unit but some usually on front Common ports: Serial Parallel Network Keyboard Mouse Monitor Phone Modem FireWire IrDA Game USB 25 Ports, Cont'd MOUSE PORT Used lo connect a mouse. KEYBOARD PORT. Used to connect a keyboard, USB PORTS: Used to connect a keyboard, mouse, scanner, flash memory drive, or other USB devices. MONITOR PORT Used to connect a manitor. SOUND PORTS Used lo connec speakers, head- phones, and a microphone. PHONE PORT Used to connect a telephone so you don’t lose the use of your phone Jack. POWER CONNECTOR Conneels PC loa Power outlet. SERIAL PORT Usually used for a scanner or mouse. PARALLEL PORT Usually used tor a printer. NETWORK PORT Used to connect the PC toa network. MODEM PORT Used to connect the PC toa phone Jack. CONNECTORS 26 Ports, Cont'd NETWORK PORT MODEM PORT MONITOR PORT S-VIDEO PORT PARALLEL PORT FIREWIRE PS 2 PORT PORT (for keyboard or mouse) SD slot SDIO Wi-Fi networking card SD flash. memory card USB PORTS 27 System clock: timing mechanism that synchronizes the computer s operations Ticks millions of time per second 1 tick per second = hertz (Hz) At each clock tick, the CPU executes one or more machine instructions 30 CPU RAMSystem bus Instructions Store results Program Instructions loaded into RAM when program startedSystem Clock Does fetch, decode, execute, store for every instruction Controls rate instructions processed 31 Machine cycle: the series of operations involved in executing a single machine instruction Fetch the program instruction is fetched from RAM Decode the instruction is decoded so it can be executed Execute the instruction is carried out Store the original data or the result is stored either in registers or in RAM, depending on the instruction 32 MACHINE CYCLE 3: The addition command is input, causing the two numbers to be added and the result stored. The Machine Cycle, Cont'd CPU ea TOLL / / Decode Unit be ET eta Ul i a (eat CPU MACHINE eee aes CYCLE 4: Output The equal cautents of Z sign Is inpu’ r causing the sum to be Oa A nee output. Unit Co eB Output Z Lp 2G! Le ee Cle RT { Hie 35 Don't run so many programs at a time Add more RAM Upgrade your disk drive to a faster one Can make a big difference Faster does not necessarily mean bigger Uninstall unused programs, delete temporary files, scan for viruses and spyware, etc. Upgrade your Internet connection Upgrade your video card Will make a difference only for games and video 36 Improved architecture (smaller components, faster bus speeds, multiple CPU cores, etc.) Pipelining: multiple instructions executed at one time Most modern PCs do this Multiprocessing and parallel processing: using more than one processor With multiprocessing, multiple CPUs run different programs at same time With parallel processing, multiple CPUs run the same program at same time Home PCs never do this, due to cost and complexity 37