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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?