IS310 Software Hardware Concept Chapter 5 to 7 Study guide Spring 2010

8/9/2019 IS310 Software Hardware Concept Chapter 5 to 7 Study guide Spring 2010

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Ch 5

Storage Device Characteristics

Speed: Most important characteristic that differentiates primary and secondarystorage.

Access time: time required to execute one complete read or writeoperation.

Average Access time: average access times on all storage locations.

Block: describes secondary storage data transfer units.

Volatility: storage device or medium that cannot reliably hold data for longperiods.

Access Method: Physical structure of a storage devices read/write mechanismand storage medium.

Serial Access: stores and retrieves data items in a linear or sequentialorder. Magnetic tapes are the only widely used form of serial access storage.

Random Access: aka direct access, not restricted to any specific orderwhen accessing data. All primary storage devices and disk storage devicesare random access devices. Access is constant for primary storage devices;but is not constant for disk storage due to, physical/spatial relationships ofthe read/write mechanisms.

Parallel Access: can simultaneously access multiple storage locations. RAMis also a parallel access device. If unit of data access is a bit, then access is

parallel. Also achieved by sub dividing data items and storing the componentpieces on multiple storage devices. E.g. operating systems storing filecontents on several disk drives.

Portability: Standardization of storage formats favors portability. Ability to beconnected or disconnected quickly to a computer. Removable storage mediahave slower access than permanently installed devices.

Cost and Capacity: Cost increases as an access method moves from serial torandom to parallel. Users sacrifice speed and parallel access to gain sufficientcapacity at an acceptable cost.


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Memory-Storage Hierarchy:

Primary Storage Devices: Critical to PSD is access speed and data transfer unitsize. PSD must closely match CPU speed and word size to avoid wait states.

Technologies applied to the construction of processors have in general, beenapplied simultaneously to the construction of primary storage devices.

Storing Electrical Signals: electrical power is stored directly by variousdevices such as batteries and capacitors. Batteries are slow toaccept/regenerate electrical current. Capacitors are rapidly faster than batteriesbut loses charge at a rapid rate and require fresh injection of electrical current atregular intervals (hundreds to thousands of times per second).

Random Access Memory: generic term describing a PSD with the following

characteristics: microchip implementation using semiconductors, ability to readand write with equal speed, and random access to stored bytes words or largedata units.

Static RAM: implements bit storage with a flip-flop circuit. Entirelyimplemented thru transistors. Volatile unless a continuous supply of power isguaranteed.

Dynamic RAM:electronic memory circuit that implements bit storage withtransistors and capacitors. Less complex than SRAM but slower due toconstant refreshing and less efficiency circuitry for accessing individual bits(10 times slower access times than SRAM). DRAM is typically 50x slower thanmicroprocessors.

Synchronous DRAM: reliable high speed method of data transmission inwhich data are sent in continuous data streams. Read-ahead RAM that usesthe same clock pulse as the system bus. Several clock cycles are required tocomplete a single random access.

Enhanced DRAM: consists of small amount of SRAM placed in each DRAMdevice. Word and several words that follow are retrieved when read request


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for specific word is retrieved. SRAM cache will store extra words inanticipation of future sequential read requests.

Nonvolatile Memory: Ram with long-term or permanent data retention (NVM).Has applications in cell phones, handheld computers, and portable storagedevices.

Firmware is software that resides on NVM or ROMs

Read Only Memory is the earliest type of NVM with data content writtenpermanently during manufacture.

Erasable Programmable ROM (EPROM) is manufactured blank, is writtenwith a special EPROM writer, and erased by exposure to ultraviolet light. Thelatest and only available type is Electronically Erasable Programmable ROM(EEPROM). EEPROM has low density, relatively high costs, and write speedthat is too slow to enable EEPROMs to serve as PSD.

Flash RAM is the most common NVM used today. Competitive with DRAM in

storage capacity and read performance. Results in cell destruction after100,000 or more write operation. Due to slow write speed and limited numberof write cycles, FLASH RAM is used for secondary storage and for firmwarethat isnt frequently updated.

Ferroelectric RAM embeds crystals of a metallic compound within the bitstorage/access circuitry. Non-volatile RAM that stores bit values withinmetallic crystal. Center is moved from of the crystal to another to representbit values. R/W operations are similar to conventional DRAM and SRAM atcomparable speeds. Ferroelectric RAM access speeds are much faster thanflash RAM but repeated read operations can destroy cell contents.

Polymer Memory uses a special plastic with electrical resistance that canbe increased or decreased by an electrical field. Advantages are low-costmaterials, nondestructive read access, and individual memory cells with notransistors. Challenges are accessing individual memory cells and finding low-cost fabrication methods.

Memory Packaging: memory circuits are embedded within microchips, andgroups of chips are packed on a small circuit board that can be installed orremoved easily from a computer system.

Dual in-inline Packages (DIPs): early form of packaging for CPU andmemory circuits with two rows of electrical contact pins. Packaging form ofearly RAM and ROM circuits. Installing DIP on a PCB is a tedious and preciseoperation, and DIPs occupy a greater portion of surface area.

Single in-line Memory Module (SIMM) small printed circuit board withmemory chips on one or both sides and electrical contacts on one edge.Standard RAM package. Incorporates tiny DIPs on a tiny PCB.

Double in-line Memory Module (DIMM) a newer packaging standard,and is essentially a SIMM with independent electrical contacts on both sidesof the module.


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CPU Memory Access:The physical organization of memory, the organization ofprograms and data within memory, and data within memory, and the methods of

referencing specific memory locations are critical design issues for both primarystorage devices and processors.

Physical Memory Organization: Addresses of these memory locations areassigned sequentially so that available addresses proceed from zero (lowmemory) to the maximum available address (high memory).

Big Endian describes architectures that store the most significant byte atthe lowest memory address.

Little Endian describes architectures that store the least significant byte atthe lowest memory address.

Addressable Memoryof a CPU is the highest numbered storage byte thancan be represented. If 32 bits are used to represent a memory address, thenaddressable memory is 2^32 or 4gb.

Physical Memoryis the actual number of memory bytes that are physicallyinstalled in the machine. Physical memory is smaller than addressablememory.

Memory Allocation and Addressing: describes the assignment of specificmemory addresses to system software, application programs and data.

Absolute Addressingdescribes memory address operands that refer toactual physical memory locations.

Indirect Addressing aka Relative Addressing is the method ofautomatically computing physical memory addresses.

Offset Registeris the register that hold offset values. Contents are addedto calculate the corresponding physical memory address.

Magnetic Storage: Exploits the duality of magnetism and electricity. The polarityof magnetic charge represents the bit values zero and one.


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Factors that lead to data loss in magnetic storage devices

Magnetic Decay and Leakage: Decreases strength of individual bit charges.Natural charge decay over time data must be written at higher power than theread threshold to avoid data loss.

Areal Density: coercible material per bit decreases as areal density increases higher areal density makes stored data more susceptible to loss due to decayand leakage.

Media Integrity: stability of coercible material and its attachment to substrate physical stress and temperature/humidity extremes must be avoided toprevent loss of coercible material.

Magnetic Tape: cancellation of adjacent charges of opposite polarity andmigration of charge to nearby areas data must be written at higher power thanthe read threshold to avoid data loss.

Linear Recording places bits along parallel tracks that run along the entire

length of tape.

Helical Scanning reads and writes data to or from a tape by rotating theR/W head at an angle to tape and moving from tape edge to tape edge.Requires much more complex r/w mechanisms.

Technology Focus Magnetic Tape Formats and Standards

Before the mid-1990s, mainframes used tape drives that used .5 or 1 inch openreel tape. IBM set standards for mainframe tapes because it made the majorityof mainframes. An alternative for smaller computers was the open Quarter InchCommittee (QIC). Digital Data Standards (DDS) standards were developedby HP and Sony from an earlier technology called Digital Audio Tape (DAT).DDS utilized helical scanning and were cheap but not meant for precisealignment, and were expensive due to being environmentally friendly for one.DDS was used widely in small servers, and DAT72 format looked to succeed it.Digital Linear Tape (DLT) is a standard developed by Quantum, and is .5

inches wide and contain a cartridge with only one reel. Longer tape lengths andhigher capacity per tape can be achieved the single reel cartridge. Sony andExabyte extended DAT with Sonys Advanced Intelligent Tap (AIT) andExabytes Mammoth standards. Both used helical scanning 8mm tapes, andemploy a more expensive and precisely manufactured tap cartridge. Both cancarry more data onto a single tape. AIT includes a small RAM cache to storedirectory information in order to speed searching and data access. Linear TapeOpen (LTO) is a standard developed by HP, IBM, and Seagate, and is aproprietary standard. LTO uses linear recording and employs a number of


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technology improvements in tape cartridges, coercible materials, r/w heads, andtape control. LTO is primarily designed for enterprise-wide servers supportingmission critical applications. Accelis Standard maximizes retrieval speed at theexpense of per-tap capacity, while the Ultrium Strandard maximizes capacityat the expense of access speed. Accelis has never been developed due to theintroduction of magnetic disks.

Magnetic Disks are flat, circular platters with metallic coatings that are rotatedbeneath r/w heads. Data are normally located on both sides of the platter.

Trackis one concentric circle of a platter, or the surface area that passesunder a read/write head when its position is fixed.

Cylinderis the set of all tracks at an equivalent distance from the edge orspindle on all platter surfaces.

Access Armis where r/w heads are mounted, on its end.

Floppy disk aka Disketteuses a base of flexible or rigid plastic materialand is 2.5 to 3.5 inches in diameter.

Disk access time depends on: switch among read/write heads; positionthe r/w heads over a track; wait for the desired sector to rotate beneath ther/w heads.

head-to-head switching time is the elapsed time required to switch sharedread/write circuitry between two adjacent r/w heads. Measured innanoseconds.

track-to-track switching time is the time required to move from one trackto another. Measured in milliseconds.

Rotational delayis the time the disk controller must wait for the propersector to rotate beneath the heads. Depends on the platter rotation speed.Increasing spin rate decreased rotational delay.

Technology Focus Pocket-Size Data Storage


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The last widely adopted improvement to the personal computer floppy diskstandard came in late 1989 the 1.4 MB 3.5 inch standard floppy still usedtoday. Floppy standards stagnated similar to that of the QIC standard. IomegaCorporation developed successful removable magnetic media including zip, jaz,and REV disks. In early 2000s, USB and flash memory were to fill the gap held byfloppy disks for decades. Flash memory matured rapidly in the late 1990s and

early 2000s. In 2003, flash memory chips with 64mb were being mass producedfor less than 10$ each.

Optical Mass Storage Devices: Came of age in 1990s. Advantages overmagnetic storage are higher areal density and longer data life. Recording densitiesare 10 times greater than magnetic storage devices. Optical storage is popular duestandardized and relatively inexpensive storage media. Manufacture of CDs is lessper bit than removable storage technologies.

CD-ROM compatible with compact disc digital audio (CD-DA) but includes

additional formatting information to store directory and file information. CD is120 millimeters (4.75 inches) in diameter. CD-DA is a standard developed bySony and Phillips for storing and distributing music.

CD-R has stable dye when scanned at low power during a read operation, butchanges its reflective properties when scanned at higher power during a writeoperation. Sensitive to light, so should be stored in a dark location at roomtemperature.

Magneto-Optical uses a laser and reflected light to sense bit values. At 150degrees Celsius, material can be charged by a magnetic field in much the sameway a purely magnetic media. Magneto Optical technology peaked in the mid1990s but was overcome by CD-RW drives. M-Os advantage over CD-RW is

access speed and capacity, but were phased out by DVD phase-change formats.

Phase-Change Optical Discs enables nondestructive writing to optical storagemedia. CD-RW is a standard of P-C Optical discs.

DVD digital video or digital versatile disc was developed by a consortium ofcompanies as standard for distributing movies and other audiovisual content. 3competing standards for RW: DVD RAM, DVD-RW, and DVD+RW.

Ch 6

System Bus: connects the CPU with main memory and other system components.Bus is a set of parallel communication lines that connect two or more devices.

Data Busmoves data among computer system components. A 64bit CPU wouldhave 64 or 128 bus data lines.


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Address Buscarries the bits of a memory address. Modern address bus, haveat least 32 lines.

Control Buscarries commands, command responses, status codes and similarmessages.

Bus Clock and Data Transfer Rate

Bus Clockis carried by control buses, and is a common timing reference forall attached devices. Its frequency is measured in megahertz (MHz).

Bus Cycle is the time interval between from one clock pulse to the next. Buscycle time is the inverse of the bus clock rate.

BCT = 1 / BCR

Bus Protocolgoverns the format, content and timing of data, memory address,and control messages sent across the bus. Every peripheral device must havethis.

Bus Masteris the CPU due to being the focus of all computer activity, while allother devices are Bus Slaves.

Besides the CPU, no other device can access the bus except in response to anexplicit instruction from the CPU.

Direct Memory Access (DMA): allows the transfer of data directly betweenmemory and secondary storage devices, without the assistance of the CPU. Withit, the DMA Controller assumes role of bus master for all transfers betweenmemory and other storage or I/O devices. As DMA controller manages bustraffic, CPU is free to execute computation and data movement instructions.

Peer-to-Peer Busis where any device can assume control of the bus, or act asa bus master for transfers to any other device.

Bus Arbitration Unitis a simple processor attached to a p2p bus that decideswhich devices must wait when multiple devices want to become a bus master.

Logical and Physical Access

I/O port: Communication pathway from CPU to peripheral device. A memoryaddress that can be read/written by the CPU and a single peripheral device. Alogical abstraction that enables CPU and bus to interact with each peripheral

device as if the device were a storage device with linear address space.

Physical access: System bus is usually physically implemented on a largeprinted circuit board with attachment points for devices.

Logical access:The device, or its controller, that translates linear sectoraddress into corresponding physical sector location on a specific track andplatter.


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Linear Address Space: A set of sequentially numbered storage location.

Device Controllers: Implement the bus interface and access protocols. Translatelogical addresses into physical addresses. Enable several devices to share access to

a bus connection.

Mainframe Channels: Advanced type of device controller used in mainframecontrollers.

Compared with device controllers: Greater data transfer capacity. Largermaximum number of attached peripheral devices. Greater variability intypes of devices that can be controlled.

Technology FocusSCSI

Pronounced skuzzy, SCSI stands for Small Computer System Interface.There have been 9 generations, the earliest being SCSI-1, and latest being Serial

Attached SCSI (SAS). SCSI bus implements both a low level physical I/O protocoland high level logical device control protocol. Can connect up to 16 devices,which are assigned a unique ID of 0 to 15. The bus can be as long as 25 meters.

The control bus transmits control and status signals. SCSI-1 had a data bus 8 bitwide, while later ones had 16 bit data bus.

Interrupt Processing: Used by application programs to coordinate data transfersto/from peripherals, notify CPU of errors, and call operating system serviceprograms. When interrupt is detected, executing program is suspended; pushescurrent register values onto the stack and transfers control to an interrupt handler.When interrupt handler finishes executing, the stack is popped and suspendedprocess resumes from point of interruption

I/O Wait States: CPU cycles that could have been devoted to instructionexecution.

Interrupt: a signal to the CPU that some event has occurred that requires theCPU to execute a specific program or process.

Interrupt Handlers: operating system service routine to process each possibleinterrupt.

Supervisor: examines the interrupt code stored in the interrupt register anduses it as an index to interrupt table. Extracts the corresponding memoryaddress and transfers control the interrupt handler at that address.

Multiple Interrupts: Categories of interrupts: I/O event, Error condition,Service request.


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Stack Processing:The mechanism that allows a program to resume executionin exactly the same state as before interruption. Area of the storage is accessedin last in, first out (LIFO) basis.

Push: When values in a CPU register is added to the stack in an operation, whena process is interrupted.

Machine State: Saved register values; values held in register.

Pop: CPU remove values on the top of the stack and loads them back into theappropriate register when an interrupt handler finishes executing.

Stack Overflow: an error that occurs when there is attempt to push valuesonto stack results at full capacity.

Stack Pointer: A special purpose register that always points to the next empty

address in the stack. Incremented and decremented each time the stack ispushed or popped.

Performance Effects

Buffers and Caches

Buffers: Small storage areas (usually DRAM or SRAM) that hold data in transitfrom one device to another. Use interrupts to enable devices with different datatransfer rates and unit sizes to efficiently coordinate data transfer.

Buffer overflow: occurs when buffer is not large enough to hold a full page.Buffer size must be at least as large as the data output unit.

Diminishing Returns: When multiple resources are required to producesomething useful, adding more and more of a single resource produces fewerand fewer benefits. Applicable to buffer size. As buffer size increases, CPU cycleconsumption decreases at a nearly linear rate, but total bus cycles decrease at adiminishing rate.


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Cache: Like buffer, this a storage area (usually RAM) that improves systemperformance.

Different from a buffer thru: Data content not automatically removed asused. Used for bidirectional data. Used only for storage device accesses.Usually much larger. Content must be managed intelligently. Primary Storage

Caches.

Cache Controller: a processor that manages cache content.

Can be implemented in: A storage device controller or communicationchannel, as a special purpose processor controlling RAM installed within thecontroller or channel.

The operating system uses part of the primary storage to implement thecache.

Cache hit: when a read operation accesses data already contained withinthe cache.

Cache Miss: When the data needed is not in the cache.

Hit Ratio: ratio of cache hits to read accesses.

Cache Swap:The result of cache miss. The cache controller guesses whichdata items are least likely to be needed in the near future, writes them to thestorage device, and purges them from the cache.

Technology FocusItanium2 Memory Cache:

Itanium 2 uses 3 levels of primary storage caching. CPU, L1 and L2 areimplemented on a single chip. L3 cache is implemented on asset of separate

chips and can be 3, 4, or 6 MB. These integrated package reduces distancebetween components, so L3 can communicate with the CPU at the CPUsclock rate. L2 cache at 256KB holds both instructions and data. L1 storeprefetch instructions. Separate L1 caches allow some streamlining ofprocessor functions when storing instruction and data. Itanium 2 can assignvarious caching modes to 2KB, 4KB, or 4MB regions of main memory. Itanium2 was designed to participate in multiprocessor computer systems. Itanium 2utilizes memory snooping to maintain consistency among their caches andmain memory.

Secondary Storage Caches: Disk caching is common in modern computersystems, particularly in file and database servers. In a file server, disk

caching performance can be improved if information about file access istracked and used to guide the cache controller by:

Giving frequently accessed files higher priority for cache retention.

Use read-ahead caching for files that are read sequentially.

Give files opened for random access lower priority for cache retention.


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Processing Parallelism: Increases computer system computational capacity;breaks problems into pieces and solves each piece in parallel with separate CPUs.

Techniques for Processing Parallelism: Multicore processors, Multi-CPUarchitecture, Clustering

Multicore Processors: Placing hundreds of millions of transistors and theirinterconnections within a single microchip.

Multi-CPU Architecture: Employs multiple single or multicore processorssharing main memory and the system bus within a single motherboard orcomputer system. Common in midrange computers, mainframe computers, andsupercomputers. Cost effective for: Single system that executes manydifferent application programs and services; Workstations.

Workstations

Scaling Up: Increasing processing by using larger and more powerfulcomputers. Used to be most cost-effective. Still cost-effective when maximal

computer power is required and flexibility is not as important.

Scaling Out: Partitioning processing among multiple systems. Speed ofcommunication networks; diminished relative performance penalty. Economiesof scale have lowered costs. Distributed organizational structures emphasizeflexibility. Improved software for managing multiprocessor configurations.

High-Performance Clustering: Connects separate computer systems with high-speed interconnections.

Used for the largest computational problems. (e.g., modeling three-dimensionalphysical phenomena)

Compression: Reduces number of bits required to encode a data set or stream.Effectively increases capacity of a communication channel or storage device.Requires increased processing resources to implement compression/decompressionalgorithms while reducing resources needed for data storage and/orcommunication.

Compression Algorithm: a specific mathematical compression techniqueimplemented as a program.

Decompression Algorithm: restores compressed data to its original or nearoriginal state.

Lossless Compression: Result of compressing and then decompressing anydata input is exactly the same as the original input. Required for applicationssuch as accounting records, executable programs, and most stored documents.

Lossy Compression: Result of compressing and then decompressing any datainput is different than, but still similar to, the original input. Usually applied tovideo and audio data.


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Compression Ratio: describes the ratio of data size in bits or bytes before andafter compression. Lossless compression ratios of 10:1 is easily achieved withword processing document and ASCII/UNICODE text files. Lossless ratio of 3:1are difficult or impossible to achieve with video and audio data.

Technology FocusMPEG and MP3

Motion Pictures Expert Group creates and evaluates standards for motion picturerecording and encoding technology. CD quality music can be compressed 6:1 andmost listeners cannot distinguish the compressed audio data from the original. MP3takes advantage of well known human characteristic of human audio perceptionsuch as inability to recognize fain tones of one frequency simultaneously with muchlouder tones in nearby frequencies (3 total advantages total). Encoder utilizes 16 bitprecision.

Ch 7

Basic Concepts of Print and Display: Share many features. Characterrepresentation methods. Measurement systems. Methods of generating color.

Matrix-Oriented Image Composition: Display surfaces, Fonts, Color, Numericpixel content.

Pixel: abbreviation for picture element. Single unit of data in a graphicimage; single point on a display image.

Resolution: number of pixels displayed per linear measurement unit. A 19-

inch flat panel display has 40 pixels per centimeter or 100 pixels per inch.

Dots Per Inch: Used in U.S. to notify that a dot is equivalent to pixel.Smaller size yields higher print quality because fine details such as smoothercurves can be incorporated into the image.

Point: Used decades ago by printer to denote 1/72nd of an inch as a standardpixel size. Its use as a printers measuring system continues, even thoughmodern printing techniques are capable of much higher resolution.

Characters: symbols of written western languages.

Font: a collection of characters of similar style and appearance.

Color

RGB: primary colors for video display. Video displays generate colors usingmixtures of red, green, and blue.

Additive Colors: Video display colors. Printing industry generates colorsusing the inverse of the primary video display colors.


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Subtractive Colors: inverse colors of additive colors.

CMY: Colors, Cyan, Magenta, and Yellow, are subtractive colors.

CMYK: the four-dye scheme.

Numeric pixel contentBitmap: stored set of numbers that describes the content of all pixels in animage.

Monochrome: can display one of two colors and thus requires only one bitper pixel.

Grayscale: capable of displaying black, white and many shades of gray inbetween.

Chromatic Depth aka Chromatic Resolution: number of distinct colors orgray shades that can be displayed.

24-Bit Color: Colors of a display featuring a chromatic depth of, 2^(3*8) or16 million. Chromatic depth depends on the number of bits used to representeach colors intensity.

Palette: a table of colors. Number of bits used to represent each pixeldetermines the table size. If 8 bits, then table has 2^8 or 256 entries.

Dithering: a process that generates color approximations by placing smalldots of different colors in an interlocking pattern.

Half-Toning: grayscale dithering.

Image Storage Requirements: Depends on number of bits that representeach pixel and on image height and width in pixels. Can be reduced with bitmapcompression. Graphics Interchange Format (GIF). Joint Photographic ExpertsGroup (JPEG). Moving Pictures Experts Group (MPEG). All compression methodsare lossy, resulting in some loss of image quality. Image Description Languages.

Bitmap Compression Formats: Graphics Interchange Format (GIF), JointPhotographic Experts Group (JPEG) for single still images, and MovingPicture Experts Group (MPEG) for moving images. These compressionmethods are all lossy, resulting in some loss of image quality.

Technology Focus Adobe Postscript and Portable Document Format

PostScript is an image description language designed primarily for printeddocuments, although it can also be used to generate video display outputs.PostScripts are composed of ASCI characters and may include numeric or textualdata, primitive graphic operations, and procedure definitions. By 1990, PostScriptwas widely used in the printing and publishing industries. Missed features such astable of contents, hyperlinks to other documents, web pages, or active objects likeexecutable programs, annotations, document properties such as copyright, anddigital signatures


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Video Display:

Character-Oriented Video Display Terminals: Integrated keyboard andvideo display surface

VDTs. Most common form of video display in 1970s and much of 1980s (untilPCs). Network computers or thin clients. New class of VDT in 1990s. Limitedprocessing capabilities.

Thin Client: a hybrid device with a mix of VDT and microcomputercharacteristics. Execute within an operating environment such as Java, webbrowser, or Windows Terminal Services.

Video Controllers: Enables communication between computer system andmonitor.

Accepts commands and data transmitted via a bus from the CPU. Generates TV-

style analog video signal, which is transmitted to the monitor. Refresh cycle andrefresh rate; video RAM; dual porting; graphics accelerators.

Monitor: a modern display device.

Video Controller: Connected to video monitor, which in turn connects to thesystem bus.

Refresh Cycle:Transfer of full screen of data from the display generator tothe monitor.

Refresh Rate: Number of refresh cycles per second, and is stated in Hertz.

Video Ram aka VRAM: different than ordinary RAM, because it can bewritten by the bus interface circuitry or video processor while it is beingsimultaneously read by display generator circuitry.

Dual Porting: Simultaneous r/w capability.

Graphics Accelerators: high performance video controllers that use morepowerful processors, and software to convert incoming IDL commands introappropriate cache contents.

Video Monitors: Separate from keyboards. Common types are:

Cathode ray tubes (CRTs): an enclosed vacuum tube. Electron gun in the

rear of the tube generates a stream of electrons that are focused in a narrowbeam toward the front surface of the tube.

Liquid crystal displays (LCDs): contains a matrix of liquid crystalssandwiched between two polarizing filer panels. A liquid crystal twists oruntwists when an electrical charge is applied. Applying electrical charge toeach display matrix cell requires transistors and wiring. Less contrast thanCRT.


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Active Matrix Display: uses one or more transistors for every pixel.

Passive Matrix Display: shares transistors among rows and columns ofpixels.

Thin Film Transistor (TFT):since 1990s this has been used to manufacture

active matrix displays.

Plasma displays: Combines elements of CRT and LCD technology. Flat panelactive matrix devices. Unlike LCDs, have no backlight and no color filters. Eachpixel contains gas that emits ultraviolet light when electricity is applied.

Printers

Inkjet Printers: Most common printing technology. Prints with liquid ink placeddirectly onto paper. Uses mechanical movement or heat to force ink out ofnozzle. Paper is drawn past moving print head. Resolution is up to 600 dpi. Has

disposable print cartridges that contain ink reservoirs, a matrix of ink nozzles,and electrical wiring and contact points.

Printer Communication:

Computer systems and an Impact printer consist of ASCII or Unicodecharacters, because character and symbols are fundamental output unit.

Inkjet and laser printers use pixels as fundamental output unit.

Inkjets and laser printers have relatively large buffers to hold a line,multiple lines, or an entire page of printed output.

Image Description Languages (IDLs) are commonly used to improveprinter performance.

Laser Printers: operates with an electrical charge and attraction of ink to thatelectrical charge.

Plotters: a printer that generates line drawings on wide sheets or rolls of paper.Can handle paper widths of up to 60 inches, which makes them ideal forproducing blueprints and other engineering drawings. Pen-based printingtechnology was the norm until the mid-1990s. P-B technology draws imagesusing one or more moving pens that are raised and lowered onto paper.

Large Format Printer: current term for plotters.

Manual Input Devices: keyboards, mice, pressure-sensitive pads, and many lessfamiliar but related devices. Until the 1980s, keyboards were the dominant form ofinputs, until the introduction of the mice.

Keyboards: For entering text and commands. Early computer systems acceptedinput via punched cards or tape.


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Keyboard Controller: an integrated microprocessor for modern keyboards,used to generate bit stream inputs.

Scan Code: coded output generated by a keyboard for interpretation by aprocessor or keyboard controller.

Pointing Devices: For pointing and selecting buttons or menu items, Fordrawing, For moving the position of cursor.

Cursor: displays of pointing device movements.

Mouse: a pointing device that is moved flat surface such as a table, desk orrubber pad.

Digitizer: consists of a digitizing tablet and pen, stylus, or both. Ideal fordrafters and artists to trace blueprints or free hand sketching.

Input Pads: digitizing tablet and tablet PCs are examples of a general classof input device. 3 common input pad technologies: Infrared, Photosensor,

Pressure-sensitive pad.

Optical Input Devices: Detect light reflected off a printed surface or object into aphotosensor

Categories. Mark and pattern sensors. Image capture devices. Mark Sensors andBar-Code Scanners.

Photosensor: converts incoming light energy into outgoing electrical energy.

Mark Sensor: scans for light or dark marks at specific locations on a page.Similar to collect data from a multiple choice test.

Bar-Code Scanner: detects specific patterns of bars or boxes. Most commontype ofbar-codes is a series of vertical bars of equal length but varyingthickness and spacing.

Scanning Laser: sweeps a narrow laser beam back and forth across the barcode. Bars must have precise width and spacing as well as high contrast foraccurate decoding.

Optical Scanners: generates bitmap representations of printed images. Brightwhite light shines on the page; reflected light is detected by an array ofphotosensors. Optical character recognition (OCR) devices combine opticalscanning technology with intelligent interpretation of bitmap content

Digital Cameras: Employ optical scanning technology to capture single or stillimages and store them as raw compressed bitmaps.

Portable Data Capture Devices: Combine a keyboard, mark or bar-codescanner, and wireless communications to a wired base station or computersystem. Provide rapid data capture (e.g., warehouse inventory control, packagerouting and tracking).

Audio I/O Devices


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Sampling: process of measuring and digitally encoding one or more parametersof analog signal at regular time intervals. Process of digitally encoding analogsound waves.

Analog-To-Digital Converter (ADC): accepts a continuous electrical signalrepresenting sound such as microphone input, samples it at regular intervals,

and outputs a stream of bits that represent the samples.

Digital-To-Analog (DAC): performs the reverse transformation, accepts astream of bits representing sound samples and generating an equivalentcontinuous electrical signal that can be amplified and routed to speakers.

Monophonic: outputs only one frequency (note) that can be generated at atime.

Polyphonic aka Multifrequency: used by most computers, sound generationhardware with built-in amplification and high-quality speakers.

Speech Recognition: process of reorganizing and appropriately responding tothe meaning embedded within spoken words, phrases, or sentences.Conceptually simple, but complicated by speaker variability, phonemetransitions and combinations, and real-time processing.

Phonemes: Individual sounds in human speech, that roughly corresponds tothe sounds of each letter of the alphabet.

Digital Signal Processor (DSP): Specialized to process continuous streamsof audio or graphical data. Commonly embedded in audio and videohardware.

Speech Generation

Audio Response Unit: generates spoken messages based on textual input(e.g., automated call routing).

Speech Synthesis: Stores individual phonemes within the system.

General-Purpose Audio Hardware: sound card, multimedia controller.Typically packaged as an expansion card that connects to the system bus of aworkstation. Sound cards include an ADC, DAC, low-power amplifier, andconnectors (jacks) for microphone, speaker, or headphone. Musical InstrumentDigital Interface (MIDI), Compact storage format.

IS310 Software Hardware Concept Chapter 5 to 7 Study guide Spring 2010

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