Looking Inside the Black Box Input Output CPU Storage –Secondary - Hard Drives –Primary - RAM, ROM.
Secondary Memory and Input/Output
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Transcript of Secondary Memory and Input/Output
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Exploring the Digital DomainExploring the Digital Domain
Secondary Memory and Input/Output
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Input/Output– exchanging data and instructions between the
user and the computer Secondary Storage
– auxiliary storage for data and instructions
I/O Subsystem
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backup or alternative storage in place of (volatile) RAM
cheaper, mass storage for long term use secondary memory devices (and
media) are distinguished by their capacities, speed, and cost
Secondary Memory (Storage)
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RANDOM ACCESS– items are independently addressed
– access time is constant
DIRECT ACCESS– items are independently addressed in regions
– access time is variable—though not significantly
SEQUENTIAL ACCESS– items are organized in sequence (linearly)
– access time is significantly variable
Types of Memory Access
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SEQUENTIAL ACCESS STORAGE DEVICES AND MEDIA (SASD)– magnetic tape
DIRECT ACCESS STORAGE DEVICES AND MEDIA (DASD)– magnetic floppy disks– magnetic hard disks– optical discs
Secondary Memory
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Memory Hierarchy I
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Memory Hierarchy II
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stores data represented by magnetized particles in linear tracks
magnetized clusters or domains are aligned to represent binary codes
Magnetic Tape
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Magnetic Tape
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LONGITUDINAL– older format used for record-keeping
SERPENTINE– used for system backups
HELICAL SCAN– high capacity formulation used for system
backups and archives
Magnetic Tape Formats
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Longitudinal (9-track)
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Serpentine (QIC)
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magnetic hard and floppy disks removable hard disks optical discs
– CD-ROM, CD-R,– WORM,– magneto-optical
GEOMETRY: TRACKS and SECTORSGEOMETRY: TRACKS and SECTORS
Direct Access Storage Devices
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CAV — constant angular velocity (e.g., floppy and hard disks)
CLV — constant linear velocity (e.g., optical discs)
Zoned CAV — number of sectors depends upon zone
DASD Media
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SEEK — controller advances read/write head to proper track
LATENCY — waits for proper sector to rotate under head
READ/WRITE — disk head scans the sector for read or write
Direct Access
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FLOPPY DISKS– 5.25 and 3.5 inch
diskettes
– 1.44 – 2.88 MBytes capacity
– access: drive speeds – 600 r.p.m.
– inexpensive, archival uses for small amounts of data
HARD DISKS– 3.5 inch has approx
3,000 tracks per side
– multiple disk, sides (cylinders)
– high capacity
– access: drive speeds – 3,600 up to 7,200 r.p.m.
– on-line storage
Magnetic Disks
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data is stored in blocks
blocks occupy sectors sectors on tracks files have names files are indefinite in
size files may be updated
(in part or whole)
Disk vs. File Organization
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Compact Disc–Read Only Memory (CD-ROM)– archived and published information– high capacity
Compact Disc–Recordable (CD-R)– recordable– readable using CD-ROM technology
Write Once, Read Many (WORM)– high capacity archival storage
Magneto-Optical Discs– erasable, high capacity, on-line storage alternative
Digital Versatile Discs (DVD)– Very high capacity, read-only storages
Optical Discs
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based on CDDA technology CLV geometry density: 16,000 tpi up to 650 MBytes nonerasable, nonwriteable
storage discs are mastered, pressed
(mass production) multispeeds drives common
CD-ROM
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discs are “burnt” one at a time
high intensity laser beam used for recording pregrooved tracks
low intensity beam for reading
attributes similar to CD-ROM
CD–R
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Magneto-Optical– combines magnetic and optical technologies
– erasable, readable-writable storage
– very high capacity
– not yet economical
Digital Versatile Disc (DVD)– successor to CD-ROM technology
– very high capacity read-only storage
– multiple disc, multiple sided storage
Other Optical Media
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keyboard mouse scanners (flatbed, slide, and drum) digital cameras sound digitizers MIDI (Musical Instrument Digital Interface) Video digitizers
Input Peripherals
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video display monitors– monochrome and color– CRT and LCD
Output Peripherals
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cathode ray tube (CRT)
phosphors excited by electron gun beams
RGB composite color horizontal scanning
pattern to refresh phosphors
CRT technology
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video display monitors– monochrome and color– CRT and LCD
printers– character, line, and page
Output Peripherals
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CHARACTER dot matrix
– low-cost, text and graphic printers
– slow-speed, low quality
inkjet– medium-priced
– general-purpose
PAGE laser printers
– high-quality
– assortment of sizes, performance, and cost
Printers
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video display monitors– monochrome and color– CRT and LCD
printers– character, line, and page
sound and voice output MIDI synthesizers
Output Peripherals