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Storage tradeoffs
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Computer Storage Fundamentals
Binary representationData are processed and stored in computer
system through the presence or absence of signals
Either ON or OFFON = number 1OFF = number 0
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Bit and Byte
Bit (short for binary digit)Smallest element of dataEither zero or one
ByteGroup of eight bits which operate as a single unitRepresents one character or number
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Representing characters in bytes
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Computers use binary system to calculate
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Measuring storage capacities
Kilobyte (KB): one thousand bytesMegabyte (MB): one million bytesGigabyte (GB): one billion bytesTerabyte (TB): one trillion bytesPetabyte (PB): one quadrillion bytes
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Direct and Sequential Access
Direct Access or Random AccessDirectly store and retrieve dataEach storage position has unique address and
can be accessed in same length of timeSemiconductor memory chips, magnetic disks
Sequential AccessData is stored and retrieved in a sequential
processMust be accessed in sequence by searching
through prior dataMagnetic tape
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Direct and sequential access
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Semiconductor memory
Microelectronic semiconductor memory chipsUsed for primary storageAdvantage:
Small sizeFastShock and temperature resistance
Disadvantage:Volatility: must have uninterrupted electric
power or lose memory
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Two types of semiconductor memory
RAM: random access memoryMost widely used primary storage mediumVolatile memoryRead/write memory
ROM: read only memoryPermanent storageCan be read but cannot be overwrittenFrequently used programs burnt into chips
during manufacturingCalled firmware
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Flash drive
New type of permanent storage
Uses semiconductor memory
Small chip with thousands of transistors
Easily transportedAlso called jump drives,
USB flash drives
Source: Courtesy of Lexar Media.
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Magnetic Disks
Used for secondary storageFast access and high storage capacity
Source: Quantum. Source: Corbis.
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Types of magnetic disks
Floppy disksMagnetic disk inside a plastic jacket
Hard disk drivesMagnetic disk, access arms, and read/write
heads in sealed moduleRAID (Redundant arrays of independent disks)
Disk arrays of interconnected hard disk drivesFault tolerant with multiple copies on several
disks
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Magnetic Tape
Secondary storageTape reels and cartridgesUsed in robotic automated drive assembliesArchival storage and backup storage
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Optical Disks
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Uses of optical disks
Image processingLong term storage of historical files of imagesScan documents and store on optical disks
Publishing medium for fast access to reference materialsCatalogs, directories, etc.
Interactive multimedia applicationsVideo games, educational videos, etc.
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Radio Frequency Identification
RFIDTag and identify mobile objects
E.g., store merchandise, postal packages, petsUse RFID chips to transmit and receive radio
signalsChips half the size of a grain of sandPassive chips:
do not have power source and derive power from signal in reader
Active chips: Self-powered
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RFID versus bar codes
RFID Scan from greater distanceCan store dataAllows more information to be tracked
Privacy concerns due to invisible nature
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Case 3: Advances in Speech Recognition Software
Computerized speech has become smarter, easier to use and more integrated with other applications
Interactive Voice Response (IVR) Early IVR systems are menu-drivenAdvanced are more conversational
Connected to other systems
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Case Study Questions
1. What are the business benefits and limitations of IVR at Verizon and others? How could their use of IVR be improved?
2. What types of business situations would benefit most from IVR technology? Which ones would benefit least?
3. Given the advancements in voice recognition software over the last 20 years, what types of new applications for IVR do you see in the next 20 years? Give examples.
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Real World Internet Activity
1. IVR is advancing rapidly in terms of its ability to simulate natural language conversations and accept common phrases. Using the Internet
Research the state of the art in speech recognition.
One good place to start is www.scansoft.com.
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Real World Group Activity
2. Simply simulating natural conversations is but one capability of speech software applications. Text-to-speech, voice verification, and speech-to-text are a few others. In small groups,
Brainstorm how speech recognition systems can be used in innovative and useful ways.
Do you think we will eventually eliminate the need for humans in common telephone interactions?
Is this good or bad?