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Introduction to Computers Lecture # 10
This document provides an overview of secondary storage devices, including magnetic storage devices like magnetic tapes, hard disks, and floppy disks. It also discusses optical storage devices such as compact discs, digital versatile discs, and Blu-ray discs. Finally, it covers flash drives. The document describes the basic components and features of these various storage technologies and how they work to store digital data.
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Introduction to Computers Lecture # 10
- 1. Introduction to Computer Lecture# 10 Course Instructor : Sehrish Rafiq Govt. Girls Degree College Maneri Swabi Higher Education Department KP
- 2. Lecture Overview • SecondaryStorage Devices Magnetic Storage Devices Magnetic Tapes Hard Disks Floppy Disks Zip Disks Optical Storage devices Compact Discs Digital Versatile Discs Blu-ray Discs Flash Drives
- 3. Secondary Memory/ Storage •Secondary memory/storage is also known as auxiliary memory/storage. • Secondary memory devices are those memory devices which are not directly accessible by the CPU. • To process data and programs stored on secondary storage must first be brought in to primary memory for processing. • Secondary storage devices are non-volatile and they provide permanent storage to data. • Secondary storage devices can store huge amount of data and for long term. • These devices can store data and programs permanently and for long term. • Examples:- Magnetic Storage Devices Optical Storage devices Flash Drives
- 4. Magnetic Storage Devices •Magnetic storage media and devices store data in the form of tiny magnetized spots. • These devices are coated with magnetic material such as iron oxide or ferric oxide to store binary data. • Stored data can be read and erased using tiny electromagnets. • Magnetic storage is a form of non-volatile storage. • This means that the data is not lost when the storage device is not powered. • There are three types of magnetic storage devices :- Magnetic Tapes Hard Disks Floppy Disks Zip Disks
- 5. Magnetic Tapes • Amagnetic tape is a long and narrow strip of plastic on which data is stored in the form of magnetized spots. • At first, the tapes were wound in wheel-like reels, but then cassettes and cartridges came along, which offered more protection for the tape inside. • One side of the tape is coated with a magnetic material. • Data on the tape is written and read sequentially. • Finding a specific record takes time, because the machine has to read every record in front of it.
- 6. Continued… • Most tapesare used for archival purposes, rather than ad-hoc writing/reading. • A device that stores and reads computer data on magnetic tape is called a tape drive, a tape unit, or a streamer. • Data is written into 'tracks' on the medium. • Older magnetic tapes used 8 tracks, while more modern ones can handle 128 or more tracks.
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- 8. Hard Disk • Ahard disk drive (HDD) is a non-volatile computer storage device containing magnetic disks or platters rotating at high speeds. • These disks or platters are made of rigid aluminum or glass. • A hard disk also contains a mechanical arm containing read/write heads known as actuator arm. • When the platters rotate, the actuator arm can write new data on them and can read the existing data from them. • Hard disk is an essential part of digital computers nowadays and is used to store huge amount of data permanently. • A hard disk drive is also known as a hard drive. • The storage capacity of hard disks nowadays is in terabytes.
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- 11. Floppy Disks •Floppy disksare thin removable diskettes made of flexible plastic. •These disks are coated with magnetic material such as iron oxide. •By the help of particles of this material computer data and programs are stored on them. •Typically they are 3.5" in diameter and capable of storing up to 2 MB of data. •These diskettes are enclosed inside square shaped plastic casing. •Data on floppy disk can be written/read by the help of a Floppy Disk Drive.
- 12. Floppy Disks • Theyare portable and were used to transfer data from one computer to another computer. • Nowadays people use USB’s instead of floppy disks.
- 13. Zip Disks • AZip disk was an advanced version of the floppy disk. • They look similar to floppy disks, but are slightly larger and thicker, and have stronger plastic casing which makes them easier to store and handle. • The magnetic coating used in Zip disks is of higher quality than that used in floppy disks, and they could store more data than floppy disks. • Like floppy disks, Zip disks are lightweight and portable. • The disk needed a special drive called the Zip drive in order to be used. • Zip disks are available in 100-250-MB capacities and are used to store, share and back up large amounts of data, which was not possible with ordinary floppy disks.
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- 15. Optical Storage Devices •Optical storage devices use optical storage techniques and technology to read and write data. • It is a computer storage disk that stores digital data in the form of slightly burnt spots. • They use laser beams to read and write data. • They are non-volatile and can store more data than magnetic tapes and floppies.
- 16. Optical Storage Devices •There are three types of optical storage devices. Compact Discs Digital Versatile Discs Blu-ray Discs
- 17. Compact Disc • CompactDiscs are often abbreviated as CD’s. • They are also known as CD-ROMs, or Compact Disc - Read Only Memory. • They are small circular plastic disks having a shining surface. • They store and retrieve computer data or music using light. • Compact Discs are faster and could hold more information than floppy disks. • CDs can hold up to 700 MB of data, which is about 80 minutes of music. • The diameter of a normal CD is 120 mm.
- 18. Digital Versatile Disc •Digital Versatile Disc abbreviated as DVD is an optical storage device like Compact Disc. • Physically, a DVD and CD look the same. • Both are of the same size and typically have one side with a label and the other side that the laser reads, unless it is a double-sided DVD. • However, DVD’s store data in compressed form which allows them to hold more data than a CD.
- 19. Blu-ray Disk • ABlu-ray disk (BD) is a high-capacity optical disk medium. • It can store large amounts of data and was designed to supersede the DVD. • Blu-ray technology gets its name from the blue-violet laser that is used to read Blu-ray disks. • Compared to a DVD’s red laser, a blue laser permits more information to be stored at a greater density.
- 20. Flash Drives • Aflash drive is a small, portable storage device. • They are often referred to as pen drives, thumb drives, or jump drives. • The terms USB drive and solid state drive (SSD) are also sometimes used. • Most flash drives have a storage capacity from 2 GB to 64 GB. • Flash drives can be written and rewritten to an almost unlimited number of times, similar to hard drives.
- 21. Flash Drives • Flashdrives have completely replaced floppy drives for portable storage and, considering how large and inexpensive flash drives have become, they've even nearly replaced CD, DVD, and BD disc for data storage purposes.