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AS Level ICT

AS Level ICT. Selection and use of storage requirements, media, and devices: Devices and media. Primary and Secondary storage. The two means of storing programs and data in a computer system are: Primary storage – this is storage that uses chips within the control, arithmetic, and logic units

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AS Level ICT

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  1. AS Level ICT Selection and use of storage requirements, media, and devices: Devices and media

  2. Primary and Secondary storage • The two means of storing programs and data in a computer system are: • Primary storage – this is storage that uses chips within the control, arithmetic, and logic units • Secondary storage – also know as backup storage, this is uses media that is outside the control, arithmetic, and logic units

  3. Secondary storage • Secondary storage is important because it allows users to: • Ensure that data is stored safely and securely so that it can be accessible at a later date • Transfer data from one computer to another

  4. Secondary storage • There are a range of different devices that can be used as secondary storage including: • Magnetic disk drives • Optical drives • Magnetic tape drives • Solid-state storage (Flash/Pen drives and Memory Card drives)

  5. Magnetic disk drives • Magnetic disk drives come in two different media: • Floppy drives – these use floppy disks • Hard drives (also known as Hard Disks)

  6. Floppy drives • Floppy disks are a removable media that fit into floppy drives • The original floppy disk was produced in 1969 by IBM • It was 8 inches across, and could store 80 kilobytes of data • It was replaced in 1975 by the 5.25 inch floppy disk

  7. Floppy drives • These were, in turn, replaced in 1984 by the 3.5 inch floppy disk • This is a flexible plastic disk, coated with a magnetic layer, within a hard plastic protective outer cover • A sliding metal cover protects the magnetised, plastic disk when it is not in the floppy disk drive • Floppy disks originally held 360 kilobytes, but the latest versions can store 1.44 megabytes

  8. Floppy drives • Because the demands for large, portable storage media has grown considerably since the introduction of the 3.5 inch floppy disk, it is now reached the end of its life as a viable, large-scale storage media • Many computers are now being sold without floppy drives and it is likely that it will soon become a museum piece like its predecessors

  9. Hard drives • Hard drives are also sometimes referred to as hard disks • Hard drives consist of a series of rigid plastic disks, each of which is covered with a magnetic surface • A hard disk spins at a speed of between 60 and 120 revolutions per second • The data stored on the hard disk is read or written by a head that floats just above the disk (less than 0.1mm!) on a cushion of air

  10. Hard drives • Because the head is so close to the surface of the hard disk, even a dust particle can cause the head to ‘crash’ into the surface • To stop this happening, hard disks are always kept inside sealed units

  11. Hard drives • The surface of a hard disk is divided up into Sectors and Tracks • Data is stored in the ‘blocks’ created by the Sectors and Tracks • Moving data into a ‘block’ is called Random Access

  12. Hard drives • Hard drives have the major advantages of having: • A very high transfer rate • A very large storage capacity • Internal hard drives can also be added to existing computers in order to increase their storage capacity, and external hard drives – often connected via a USB – can be used as both additional storage and as a removable backup media

  13. Optical drives • Optical disks are a removable media that fit into optical drives • They are flat circular disks that are covered with surface that can be ‘burned’ with a laser to create prismatic ‘bumps’ • The ‘bumps’ are used to store data • The ‘bumps’ can then be ‘read’ by a light beam that reflects from the ‘bumps’ • A read/write optical drive contains the laser that ‘burns’ the optical disk and the light beam that ‘reads’ it

  14. Optical drives • There are a variety of different optical disks available: • CD-ROM – Compact Disk – Read Only Memory • CD-R – Compact Disk - Recordable • CD-RW – Compact Disk - Rewriteable • DVD – Digital Versatile Disk • DVD-ROM – Digital Versatile Disk – Read Only Memory • DVD+RW – Digital Versatile Disk + Read/Write

  15. Compact disk – CD-ROM • This is the most common type of CD available, and is the way in which most modern software is supplied to individual personal computers • With CD-ROMs: • Data is read only • Data is stored as an optical pattern on the surface of the disk • Storage capacity is 600 megabytes • Can used for the distribution of software

  16. Compact disk – CD-R • These are supplied ‘blank’ and can be ‘written to’ by CD-Writer drives • They can be used to store large amounts of data, but once used, they can not be re-used • They are ideal for use as a backup storage media or to store digital music

  17. Compact disk – CD-RW • These are supplied ‘blank’ and can be ‘written to’ by CD-Writer drives • They can be used to store large amounts of data, and can be ‘written to’ many times, just like a hard drive • However, the transfer rate is slower than that of a hard drive, and it is not as robust

  18. Digital versatile disk • The DVD was originally called the Digital Video Disk, but once it was realised how much data they could to store, the name was changed to reflect the disk’s versatility • The DVD is now replacing the CD as the main method of bulk saving data on personal computers • The reason for this is that they are capable of storing much larger amounts of data • A DVD can store 17 gigabytes of data; this is equal to 26 CD-ROMs or 12,000 floppy disks!

  19. Digital versatile disk – DVD-ROM • These are mainly used for the distribution of movies • DVD-ROM drives can read CD-ROMs

  20. Digital versatile disk – DVD+RW • These are supplied ‘blank’ and can be ‘written to’ by DVD-RW and DVD+RW drives • The difference between the two types of rewriteable DVD is in the dye used on the surface of the DVD • DVD-RW can be read by all DVD drives, but DVD+RW can only be read by the more modern DVD drives

  21. Digital versatile disk – DVD+RW • Older DVDs have a storage capacity of 4.7 gigabytes whereas the latest ones can store up to 8.5 gigabytes

  22. Disk access time • Disk access time is sometimes used to describe the speed at which different drives can access information. • It is defined as the amount of time it takes for the drive’s head to reach the correct ‘block’ on a disk so that the data that has been selected can be accessed • This can take up to 15 milliseconds for a hard disk and longer for other disk media

  23. Magnetic tape drives • Magnetic tape drives store data on plastic tape that is coated with a magnetic surface • The tape is then stored on a reel or within a cartridge/cassette • It is a cheap method of storing large amounts of data that does not need to be accessed quickly • As a result, it is often used as a ‘backing store’ for large and mainframe computers

  24. Magnetic tapes – Reel-to-reel Reel-to-reel magnetic tape in use with a large or mainframe computer

  25. Magnetic tapes – Cartridge/cassettes A 400 gigabyte magnetic tape data cartridge or cassette This would primarily be used a backup storage for a large or mainframe computer

  26. Solid-state storage • The use of solid-state storage devices (i.e. devices that use memory chips) in removable media has grown considerable over recent years • The two most common solid-state storage devices in use are: • Flash/pen drives (also known as USB memory sticks or thumb drives) • Memory cards

  27. Flash/pen drives • These have become very popular because they are cheap, portable, and have a reasonably large storage capacity (typically 1 to 8 gigabytes) • They are a printed circuit board encased in a protective plastic case, and they interface with a computer via a USB connector

  28. Flash/pen drives - Advantages • The main advantages of flash/pen drives are: • They are small and lightweight • They can interface with any computer that has a USB connector • They can store relatively large amounts of data • They are reliable as they have no moving parts that can break • It is very difficult to damage data that is stored on a flash/pen drive

  29. Flash/pen drives - Disadvantages • The main disadvantages of flash/pen drives are: • They can be easily lost or stolen • They have a slower transfer rate than a magnetic hard drive

  30. Memory cards • These have become very popular as a storage media for use with digital cameras although they can be used to store any digital data • They are a printed circuit board encased in a protective plastic case, and they interface with a camera or computer via a special connector • They are very lightweight but must always be kept in a protective box when not in use as the special connectors can easily be damaged

  31. Memory cards • Examples of the different types of memory cards • These include: • CompactFlash (CF Card) • Secure Digital Card (SD Card) • MultiMediaCard (MMC) • Sony Memory Sticks • SmartMedia • xD-Picture Card

  32. AS Level ICT Selection and use of storage requirements, media, and devices: Devices and media

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