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Storage devices

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Storage • Storage device : stores data and programs

permanently its retained after the power is turned off.

• The most common type of storage device is hard drive.

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Storage• All information on computers are stored in files.• The computer store data in the form of bytes

(8-bit) a storage medium can hold a number of Bytes .

• A byte is approximately one character ( letter ‘a’, number ‘1’ , symbol ‘?’ etc…).

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1 -Bit : the smallest unit. It holds a single value, ether 1’s or 0’s.

2 -Byte : A byte consist of 8 bits.[Byte=8bits]3 -Kilobyte : consist of 1024 bytes.[KM=1024bytes].

4 -Megabyte : consist of 1024 KM.[MB=1024KM].5 -Gigabyte : consist of 1024 MB.[GB=1024 MB].

6 -Terabyte : consist of 1024 GB.[TB=1024GB].

Units of Measurements

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TYPES OF Storage

Primary storage(Internal storage)

Secondary storage(External storage)

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Storage

• Primary storage– Volatile storage(changeful)– Temporary storage

• Secondary storage– Nonvolatile storage– Permanent storage

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Secondary Storage• Secondary storage permanently saves information for future use; to

share information with others; to modify at later date.• Secondary storage is nonvolatile – stores programs and data as

opposed to temporary storage (RAM).

• Characteristics include:• Media or medium – actual physical materials that holds the data and

programs.• Capacity – measures how much a particular storage medium can hold.• Storage devices – hardware that reads data and programs from storage

media (most also write to storage media).• Access speed or access time – measures the amount of time required by

the storage device to retrieve data and program.

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Secondary Storage• Writing – process of saving information to the

secondary storage device.

• Reading – process of accessing information from secondary storage.

Secondary Storage Devices - Examples of secondary storage devices : floppy disks, hard disks, and optical disk drives.

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1-Floppy Disk Drives (FDD)

- Floppy disk called diskettes : are Portable or removable storage media , inexpensive.

- Typically used to store and transfer small word processing, spreadsheet, and other types of files.

- Also called flexible disks and floppies- Stores 100 MB, 250 MB or 750 MB capacity

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2-Hard Disks

*Faster than a floppy diskette *Large capacity

*Today the standard hard disk stores 150 GB or more.

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Types of Hard Disks

1 -Internal Hard Disk

2 -External Hard Disk

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Internal Hard Disk

-Located inside the system unit-Used for storing the operating system, other

programs, and large data files -You should perform routine maintenance and

periodically backup all important files

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Internal Hard Disk

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External Hard Disk

*An external hard disk is easy to use.*Located outside the system unit.

*The same as internal hard disk, more expensive.

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3 -Optical Disks

-Use laser technology to provide high capacity storage. -It is flat, circular, plastic or glass disk on which data is

stored in the form of light and dark pits . -The two most common are:

1-Digital Versatile Disc (DVD)

2-Compact Disc (CD)

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3 -Optical Disks

• Compact, high capacity form of permanent storage (up to 50 gigabytes of data).

• Optical discs are read by an optical disc drive.• Laser beam writes by creating a pattern of pits (holes) and lands (flat

areas) to encode data bits.• Laser beams reflect off the pits and lands to read the data.• Rotational speed determines how fast data can be transferred from

the CD.• Optical disks come in many different sizes. • Most common is 4 ¾ inches.• Stored in a protective case called jewel boxes.

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Compact Disc (CD)

*Three basic types of CD’s : -Read only: CD-ROM

-Write once: CD-R-Rewriteable: CD-RW

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1-Read only CD-ROM: compact disk read only memory and cannot be erased or modify contents.

2-Write once CD-R: ( compact disk-recordable) disk you can write to only once.

3 -Rewriteable CD-RW: (compact disk-rewritable) Erasable disk you can write on many times , that can

be erased and written to with the new information.

Compact Disc

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Digital Versatile Disc (DVD)

*Digital Versatile Disc or Digital Video Disc (DVD)*Similar to CDs, but can store more data

*Three basic types:-Read only: DVD-ROM

-Write once: DVD+R; DVD-R-Rewritable: DVD+RW; DVD-RW; DVD-RAM

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1- Read only -DVD-ROM: Known as DVD players.Used for videos .

2-Write once -DVD-R and DVD+R: Write once formatTwo competing write once formats.

Used to create permanent archives for large amounts of data and to record videos.

3-DVD-RAM or DVD+RW or DVD-RW– rewritable:Use to store video from camcorders and developing large multimedia presentations that include extensive graphics and video

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Other Types of Storage 1 )Solid-state storage

• Flash memory cards.

• USB drives .

2) Magnetic tape.

• VCR tape (Video Cassette Recorder ).

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Other Types of Storage Solid-state storage • No moving parts.• Reliable, but expensive. • Requires less power.Magnetic tape • Slower sequential access.• Stores data and programs. • Used for making backups of data.

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Solid-State Storage

• Flash memory cards : -Widely used in notebook computers

-This type of storage device has no moving parts. -They are commonly used in many electronic devices,

including : digital cameras, mobile phones, laptop computers, MP3 players, and video game consoles.

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• USB drives -Also known as flash drive , pen drive , or key

drive. -Connects to a USB port

-Easy to use and flexible, a cheap .price, called a removable disk, multiple forms

Solid-State Storage

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Identify the Device

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Identify the Device