computer memory ,.,
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its very useful for presentation and for understand that actual meaning of computer memory and its type ,, u like it . ,TRANSCRIPT
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MEMORY
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Hard Drive – storage RAM – memory
Memory vs. Storage
Storage, also known as mass media or auxiliary storage, refers to the various media on which a computer system can store data.
Storage devices hold programs and data in units called files.
Memory is a temporary workplace where the computer transfers the contents of a file while it is being used.
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CLASSIFICATION- BIG PICTURE
Primary
Secondary
Volatile
Registers
Cache (I, II, III)
RAM
SRAM
DRAM
SDRAM
EDRAMEDOFLASH RAM
Non-volatile
ROM
PROM
EPROM
EEPROM
Magnetic memoryTapeHD, Zip Disk
FDD
Optical Memory
CD-ROM, CD-R, CD-RWDVD-ROM, DVD-RDVD- RW
(Semiconductor – chip). Main Memory
(Devices)
2ns
5ms
Memory Types &
Storage Devices
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Why Is Storage Necessary?
Storage devices:Retain data when the computer is turned off
Are cheaper than memory
Play an important role during startup
Are needed for output
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Storage Devices
Storage devices are categorized by:The type of operations they perform
The method they use to access the information
The technology they use
Their location in the storage hierarchy
Their capacity and speed
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Sequential vs. Random Access Storage
Sequential – Storage devices that read and write data in a serial (one after the other) fashion
Random-Access – Storage devices that read and write data without going through a sequence of locations
Tape Drive – sequential storage
Hard Disk – random-access storage
Floppy Disk Drive – random-access storage
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Storage Technologies: Magnetic and Optical
Magnetic – Storage devices use disks or tapes that are coated with magnetically sensitive material
Optical – Storage devices that use laser beams to read patterns etched into plastic disks
Magnetic Storage Optical Storage – CD/DVD drive
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The Storage Hierarchy The three levels of storage hierarchy are:
Online storage – Also called primary storage, it is made up of the storage devices that are actively available to the computer system. User action is not required.
Near-online storage – Also called secondary storage, it is not readily available to the computer system. The user performs an action, such as inserting a disk, to make it available.
Offline storage – Also called tertiary storage or archival storage, it is not readily available to the computer system. Devices such as tape backup units store data for archival purposes.
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Floppy Disk Hard Drive CD ROM / DVD
Capacity – 720 KB to 1.44 MB
Access Time – 100ms
Capacity – Up to 80 GB
Access Time – 6 to 12ms
Capacity – CD-ROM 650 MB; DVD 17 GB
Access Time – 80 to 800ms
Storage Capacity and Speed
A storage device’s performance is measured by: Capacity – The number of bytes of data that a device can
hold Access Time – The amount of time, in milliseconds (ms),
it takes the device to begin reading data
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Platter
Read/Write head
Hard Disks
Hard disks are high-speed, high-capacity storage devices.
They contain metal disks called platters. They contain two or more stacked platters with
read/write heads for each side. Hard disks can be divided into partitions to enable
computers to work with more than one operating system.
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Floppy and Zip Disks and Drives
A disk or diskette is a portable storage medium.
High-density floppy disks that are commonly used today store 1.44 MB of data.
Disks work with a disk drive. Zip disks store up to 750 MB of data and are
not downwardly compatible with floppy disks.
Zip DriveFloppy Drive
Floppy Disk
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CD-ROM Discs and Drives CD-ROM stands for Compact
Disc-Read Only Memory. CD-ROM drives can not write
data to discs. They are capable of storing
650 MB of data. They are used for storing
operating systems, large application programs, and multimedia programs.
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CD-R and CD-RW Discs and Recorders
CD-R Discs can be read
and written to Discs can only be
written to “once” CD-R drives are
capable of reading and writing data
CD-RW Discs can be read and
written to Discs are erasable Discs can be written
to many times CD-RW drives are
capable of reading, writing, and erasing data
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DVD-ROM Discs and Drives
DVD stands for Digital Video Disc. DVD technology is similar to CD-
ROM technology. DVDs are capable of storing up to
17GB of data. The data transfer rate of DVD
drives is comparable to that of hard disk drives.
DVD-R and DVD-RW drives have the ability to read/write data.
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Solid State Storage Devices
Solid state storage devices use nonvolatile memory chips to retain data.
They do not have moving parts. They are small, lightweight, reliable, and
portable.
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Compact Flash Memory
Flash Memory
Smart Card
Micro Drive
Memory Stick
PC Card
Solid State Storage Devices
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