Storage Devices Storage Store information Storage involve two

Storage Devices

Storage • Store information • Storage involve two processes: • Writing or recording the data so it can be found later for use, • Reading the store data, then transferring it into the computers memory.

Storage • The physical materials on which data is stored are called storage media. E. g. , diskette. • The hardware components that write data to, and read data from, storage media are called storage devices. e. g. , diskette drive.

Store Information • A storage device is a hardware device designed to store information. There are two types of storage devices used in computers; a 'primary storage' device and a 'secondary storage' device. Primary storage Secondary storage

Storage Devices Ø Ø Ø Storage devices are used to store data and programs permanently These devices are used to store large volume of data and program Also called backing storage devices , secondary storage devices, or auxiliary devices p. 354 Fig. 7 -1 Next

Storage • How does volatility compare? Nonvolatile Volatile Ø Storage medium is nonvolatile—contents retained when power is off Ø Memory is volatile—holds data and instructions temporarily p. 356 ON OFF Screen Display appears Display disappears Memory (most RAM) Data and instructions available to user Data and instructions erased Storage Medium (floppy disks, hard disks, CDs) Contents available to user Contents retained Next

Types of Storage Media Ø Magnetic Disk Ø Optical Disk

Magnetic Disk Ø It is most widely used storage media. Ø A magnetic disk is a thin, circular metallic plate coated with magnetic material. Ø Information can be recorded on or read from the magnetic surface Following are the types of Magnetic Disks: 1. Floppy Disk 2. Hard Disk

Magnetic Disks • What is a floppy disk? Ø shutter Portable, inexpensive storage medium (also called diskette) shell liner Thin, circular, flexible film enclosed in 3. 5” wide plastic shell magnetic coating metal hub flexible thin film

Magnetic Disks • What is a floppy disk drive? Ø Device that reads from and writes to floppy disk § Ø One floppy drive, named drive A Also called secondary storage Floppy disk drive built into a desktop computer External floppy disk drive attaches to a computer with a cable Next

Magnetic Disks • What is a write-protect notch? Ø Ø Small opening with a cover that you slide Protects floppy disk from being erased accidentally write-protected notch open means you cannot write on the disk not write-protected notch closed means you can write on the disk Next

Magnetic Disks • What is a hard disk? Ø Ø Ø hard disk installed in system unit High-capacity storage Consists of several inflexible, circular plate that store items electronically Components enclosed in airtight, sealed case for protection Next

Magnetic Disks • • Ø Ø Ø Characteristics of Hard Disk: Some important characteristics of Hard Disk are as follows: It provides large storage capacity The capacity of computer hard disk is in GB and more It is much faster than Floppy Disks It is used for storing data and programs It is more reliable than floppy disk Data stored on hard disk is safer than floppy disk

Optical Discs • What are optical discs? Ø Ø Ø Flat, round, portable metal discs made of metal, plastic Optical disk uses laser technology to read and write data Most PCs include an optical disc drive Can be read only or read/write Optical disk storage capacity is from 600 MB to over 1 GB with 14, 500 tracks per inch (tpi). It is much safer than magnetic media Push the button to slide out the tray. Insert the disc, label side up. Push the same button to close the tray. Next

Optical Discs • How should you care for an optical disc? Do not expose the disc to excessive heat or sunlight Do not eat, smoke, or drink near a disc Do store the disc in a jewel box when not in use Do not stack discs Do hold a disc by its edges Do not touch the underside of the disc p. 368 Fig. 7 -22 Next

Optical Discs • Categories of Optical disks: 1. CD 2. DVD • CD: Ø Stands for Compact Disk Ø It is most widely used media today Ø A single CD can store from 650 MB to 1 GB Ø The contents of CD can be read by CD drive Different types of CDs are as follows: 1. CD-ROM 2. CD-R 3. CD-RW

Optical Discs • What is a CD-ROM? Ø Ø Compact disc read-only memory Cannot erase or modify contents Typically holds 650 MB to 1 GB Commonly used to distribute multimedia and complex software Next

Optical Discs • What are CD-Rs and CD-RWs? Must have CD recorder or CD-R drive CD-R (compact disc-recordable) — disc you can write on once c Cannot erase disc’s contents CD-RW (compact disc-rewritable) — erasable disc you can write on multiple times ce Must have CD-RW software and CD-RW drive Next

Optical Discs • Digital Video Disk (DVD) ØIt is similar to CD-ROM ØIt uses laser beams ØIts storage capacity is much greater than CD-ROM ØIt can store up to 17 GB of data Ø High capacity disc capable of storing 4. 7 GB to 17 GB Ø Must have DVD-ROM drive or DVD player to read DVD-ROM Ø Stores databases, music, complex software, and movies Next

Optical Discs 1. DVD-R – Stands for Digital Video Disk Recordable – It is similar to CD-R – The user write data on DVD-R only once but can read many times – The data written on it cannot be erased 2. DVD-RW – it stands for Digital Video Disk rewritable – The user can write data on it many times by erasing the existing contents

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