Presentation on theme: "Storage Devices and Media"— Presentation transcript:
1 Storage Devices and Media ObjectivesUnderstand the difference between internal memory & backing storageBe able to identify different types of storage devices & mediaIdentify the uses, advantages & disadvantages of different types of storage devices & media
2 Difference between internal memory & backing storage Internal memory is the memory that is occupied by the current data and instruction being dealt with.Its contents are lost when the computer is turned off.Backing storage is the additional memory which is used to store data & instructions that we may need to use again.Hard Disk & DriveFloppy Disk & DriveOptical Disk DriveUSB Storage DevicesMagnetic TapeIts contents are NOT lost when the computer is turned off.
3 Difference between internal memory & backing storage Internal memory, also known as Immediate Access Storage (IAS) is:SmallFastVolatileBacking storage is:LargeNon –VolatileNot very fast to read from.
4 How do we measure the size of memory? Storing an individual character such as a letter, number or other character needs a set amount of space called aByteTo store 1024 characters we need 1024 Bytes or 1Kilobyte (1Kb)1 million bytes (or 1000Kb) is called I Megabyte (Mb)1000 Mb is called 1 Gigabyte (1Gb)
5 Hard disk drivesThe Hard Drive is the DEVICE which reads & writes to the Hard DiskThe Hard Disk is the STORAGE MEDIAIt’s Magnetic mediaData is stored magnetically onto tracks on the diskDisk rotates at high speed – passing under the read/write headsRead/write heads READ the data into main memory and WRITE data back to the disk after it has been dealt with
6 Hard disk drives Uses Advantages Disadvantages Stores software Stores your data filesAdvantagesLarge storage capacityStored items are not lost when the computer is switched off.Usually fixed inside the computer, so can’t get lost.DisadvantagesSlower than IASIf the hard disk crashes the computer will not work & you have lost your work!!!
7 Floppy disks & drives Uses Advantages Disadvantages To keep personal dataKeep extra copies of dataAdvantagesCan be carried with youDisadvantagesLimited capacity (typically 1.44Mb)Unlikely to store your ICT coursework on one disk
8 Zip DrivesZip drives are similar to floppy drives because the individual disks are removable and portable but they hold much larger amounts of dataTypically between 100 MB and 2 GB.
9 Optical disk drives CD Rom Uses Advantages Disadvantages Compact Disk Read Only MemoryKnown as WORM devices Write Once Read Many times.UsesStoring softwareReference material (multimedia)AdvantagesData cannot be erasedPortableMuch larger capacity than floppy disks (about 650Mb)DisadvantagesCan get lostCan’t write data to a CD RomData access can be slower than a hard drive.
10 Optical disk drives DVD Uses Advantages Disadvantages Digital Versatile DiskUsesStoring high quality audio & videoAdvantagesData cannot be erasedPortableMuch larger capacity than floppy disks and CD Rom (about 4.7 Gb)DisadvantagesCan get lostCan’t write data to a standard DVD
11 Optical disk drives CD Rewriter Uses Advantages Disadvantages Back up software & data filesCopy music filesAdvantagesPortableCan store much larger files than floppy disksDisadvantagesCan get lostCan’t always be read in some Optical drives
12 Optical disk drives DVD Rewriter Uses Advantages Disadvantages Back up software & data filesCopy video filesAdvantagesPortableCan store much larger files than CD R’sDisadvantagesCan get lostCan’t always be read in some Optical drives or DVD players
13 USB storage devices Recent development Fits on a key ring Smallest storage capacity is about 32Mb = about 22 floppy disks1Gb versions now availableIs this the end of the floppy disk?
15 Storage used for back-ups Magnetic tapeComes in two forms; tape reels, and cassettes or cartridges.Large tape reels are used to make backup copies of programs and data on large mainframe computers.Cartridges are used to make backup copies of the programs and data on personal computers and networks.The main advantage of using magnetic tape as backing storage is that it is relatively cheap and can store large amounts of data.
16 Direct and serial access Floppy disks, hard disks CDs and USB storage devices all allow direct access to data.Direct access means that the required data can be found straight away without having to read through all the data on the disk.Magnetic tape allows only serial access to data. To locate data on a magnetic tape it has to be searched from the beginning until the required data is found.
17 File compressionFile compression software can be used to make files smaller so that more data can be stored in the same amount of space on backing store.When a compressed file on backing store needs to be used it must be decompressed.This can be done using decompression software or by setting files up to be self-extracting which means that they can automatically decompress themselves.Winzip is an example of software that can be used to compress and decompress files.