Unit 3 storage fundamentals
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STORAGE FUNDAMENTALSUNIT-3
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COMPUTER SYSTEM COMPONENTS
Central Processing Unit
OutputDevices
CacheMemory
Primary Storage
SecondaryStorageDevices
ControlUnit ALU
SpecialPurposeProcessors
Output Devices
InputDevices
Short Review
Communication Devices
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Primary storage Volatile Temporary
STORAGE Secondary
storage Nonvolatile Permanent
Secondary storage characteristics Media Capacity Storage devices Access speed
RAMROMRead-Only-Memory
Random-Access-Memory
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RAM or Random Access Memory “Waiting room” for computer’s CPU. Holds instructions for processing data,
processed data, and raw data. Data stored in RAM can be modified . RAM
is a volatile storage . Data will lose after switching off the computer.
Ram is measured by: Capacity (in Megabytes or Gigabytes) Speed (in Nanoseconds)
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MEMORY (RAM) Amount of RAM installed will determine.
Which software applications will run (efficiently)?How many software applications can be open simultaneously (multitasking ability)?
RAM upgrades are cost-effective and easy to install.
All software applications will have RAM specifications listed on their packaging.
Many applications list both a minimum and a recommended amount of RAM necessary to run the software.
E.g. DDRam, DDR-2 Ram
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There is a type of memory that stores data without electrical current; it is the ROM (Read Only Memory) or is sometimes called non-volatile memory as it is not erased when the system is switched off.
Data stored in ROM cannot be modified. ROM works slower than the RAM memory. ROM is a non-volatile storage . Data remains
unchanged even after switching off the computer. E.g. EPROM, EEPROM
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Secondary storage is computer memory that is not directly accessible to the CPU of a computer, requiring the use of computer's input/output channels.
It is used to store data that is NOT in active use.
It is usually slower than primary storage but it always has higher storage capacity. It is non-volatile.
Data remains unchanged even after switching off the computer.
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Magnetic Storage
stores data by magnetizing microscopic particles on
the disk surface.
Examples: floppy disk, hard disk, tape
Optical Storagedata is read using laser light
and is possible to see data through a high
powered microscope.Examples CD and DVD
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Secondary Storage Devices
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Floppy Disks Diskettes or floppies Capacity 1.4MB 3½ inch disk Labeled 2HD data can be saved on
both sides Portable storage media Floppy disk drives (FDD)
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Parts of a Floppy Shutter slide - metal component that
opens when disk is inserted in the drive. Labels - applied to external surface to
identify contents. Write-protect notch - when open,
prevents data to be written to the disk. Protects the disk from accidentally writing
over it.
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Traditional Floppy Diskette
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Hard Disks Use thicker, metallic platters for
storage
Faster than a floppy disketteSpeed is measured in rotations or revolutions per minute (rpm)
Large capacity
Sensitive instruments
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Types of Hard Disk There are three different types of hard disks;
internal hard disk hard disk cartridge hard disk pack
All disks use a file system (File Allocation Table) to keep track of the names and locations of files that reside on a storage medium.
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Internal Hard Disk
Located inside system unit Known as a fixed disk Designated as the C drive Advantages over floppies
Access speed Capacity
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Optical Disks
Are permanent storage media that use laser technology to store data.
Optical disks can be 3½ , 4¼ , 5¼ ,8, 12 and 14 inches.
Most common size is 4¾ and is stored in a jewel box.
Two common formats are:- CD - Compact Disk DVD - Digital Versatile Disk or Digital
Video Disk
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Optical format From 650 MB to 1 GB capacity Rotation speeds vary Types
Read only: CD-ROM Write once: CD-R Rewriteable: CD-RW
Compact Disc
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Compact Disc CD-ROMs
read only - cannot be written on or erased by the user.
used to distribute databases, reference and software.
Write once - CD-R can be written to once but can be read many times
(WORM). CD burners are used to write data onto the disk.
Rewritable - CD-RW erasable optical disk, write many times, read many
times. Disk surface is not permanently altered so can be
written to, erased and written again.
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Digital Versatile Disc Digital Versatile Disk or Digital Video
Disk (DVD) Similar to CDs, but can store more data
[can store 4GB to 17GB of data] Types
Read only Write once Rewritable
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Other Type of Secondary Storage Devices
USB Flash Drives They are flash memory data storage devices
integrated with a USB interface. They are typically small, lightweight, removable
and rewritable . Data capacity: 512MB, 1GB, 2GB, 4GB, etc.
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Flash memory cards Widely used in notebook computers, Cell phones, etc. Used to record MP3 music files
Magnetic tapes External storage Provides sequential access
Information stored in sequence Slower than disks which provide direct access
Other Type of Secondary Storage Devices
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TYPES OF ROM
PROM (Programmable Read only Memory): it uses fusible links that can be burned by using special PROM burning circuit. It can be programmed by the user using a PROM programmer.
EPROM (Erasable Programmable Read only Memory): the information stored in an EPROM can be erased by exposing the memory to ultraviolet light.
EEPROM (Electrically Erasable Programmable Read only Memory): it is also same as EPROM but the erasing is done by electrical signals.
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TYPES OF RAMSRAM (Static RAM): It uses flip flops for storage elements. In SRAM once data is written into memory location, the data stays unchanged unless some new data is entered into that location.
DRAM (Dynamic RAM): It uses capacitors as storage element. The dynamic RAM contents may change with time due to leakage of charge. So it is required to refresh the storage elements periodically. It consumes less power compare to SRAM.
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Questions?