1. 1 Introduction to Computers Day 5

2. 2 Magnetic Tapes Very popular with mainframe computers Storage density is expressed in ‘bytes per inch’ (bpi) or character per inch (cpi) Storage density varies with the quality of the tape & the equipment used to read form and write on it.

3. 3 Inter record Gap for logical records on tape to be individually accessible, they must be separated by gaps. Logical records IRG s

4. 4 Inter block Gap if records can be grouped into blocks (physical records), then process is faster and less tape is wasted because fewer gaps, in this case called inter block gaps (IBG). Logical records IBG s

5. 5 Digital Tape Magnetic tape –A tape made of thin plastic with a magnetizable layer on which data can be stored Digital tape store data in digital format, instead of analogue format

6. 6 ZIP Devices Zip drive (portable or internal) uses a special 3.5 inch disk that holds 100 Mb or 250 MB.

7. 7 Optical disk storage system Data recording is done by using laser technology common type of optical disk Compact Disk Read Only Memory (CD-ROM) Compact Disk Recordable (CD-R) Write Once Read Many times (WORM) Erasable Optical Disk (EOD) Optical card

8. 8 CD-ROM Holds approximately 650 MB Used for –Data Storage –Encyclopaedias –Catalogues –Games –Entertainment –Movies –Magazines and books

9. 9 DVD Devices Originally - Digital Video Disk (DVD) Now - Digital Versatile Disk (DVD) Refers to a storage medium that can store TV- quality images on a CD-ROM disk with a capacity exceeding 5 GB