1Copyright © Prentice Hall 2000 Storage and Multimedia Chapter 5 The Facts and More

2Copyright © Prentice Hall 2000 Secondary Storage Secondary Storage allows for semi- permanent storage of information. InputProcessing Output Secondary Storage

3Copyright © Prentice Hall 2000 Benefits of Secondary Storage By separating storage from the computer, a number of benefits can be derived: Secondary Storage Space Space Reliability Reliability Convenience Convenience Economy Economy

4Copyright © Prentice Hall 2000 Space A diskette can hold the equivalent of 500 printed pages.A diskette can hold the equivalent of 500 printed pages. An optical disk can hold the equivalent of 500 books.An optical disk can hold the equivalent of 500 books.

5Copyright © Prentice Hall 2000 Reliability Data in secondary storage is basically safe. Sometimes, however, disks do fail.

6Copyright © Prentice Hall 2000 Convenience Locating and accessing electronic data is much easier and faster than non- electronic means of storing information. ? ? ?

7Copyright © Prentice Hall 2000 Economy Together, space-saving, reliability, and convenience lead to cost savings for businesses. These savings are then passed on to customers.

8Copyright © Prentice Hall 2000 Magnetic Storage of Data Data is represented as magnetized spots on a disk. data

9Copyright © Prentice Hall 2000 Bits on a Disk A magnetized spot represents a 1 (bit). The absence of a magnetized spot represents a 0 (bit).

10Copyright © Prentice Hall 2000 Reading Data from Disk Reading data on a magnetic disk means converting the magnetized data into electrical impulses and sending them to the processor. Processing Secondary Storage

11Copyright © Prentice Hall 2000 Writing Data to Disk Writing data onto a magnetic disk means to convert electrical impulses from the processor into magnetic spots on the disk. Processing Secondary Storage

12Copyright © Prentice Hall 2000 Types of Storage Media There are various types of storage media: DiskettesDiskettes Hard disksHard disks Optical disksOptical disks

13Copyright © Prentice Hall 2000 Diskettes Diskettes are made of a flexible mylar disk enclosed in a hard casing. Advantages of diskettes: portability portability easy backup of files easy backup of files new software releases new software releases

14Copyright © Prentice Hall 2000 Anatomy of a Diskette Read/write opening Sector hole Disk Shutter Casing Write- protect opening

15Copyright © Prentice Hall 2000 Zip Drives Iomegas Zip Drive holds 100 Megabyte disks, seventy times the capacity of traditional diskettes.

16Copyright © Prentice Hall 2000 Hard Disks A hard disk is a metal platter coated with magnetic oxide that can be magnetized to represent data.

17Copyright © Prentice Hall 2000 Benefits of Hard Disks Sizemore data can be stored on a hard disk than on a diskette.Sizemore data can be stored on a hard disk than on a diskette. Necessary for graphicslarger storage capacity is required for audio, graphic, and video files.Necessary for graphicslarger storage capacity is required for audio, graphic, and video files. Faster accessFaster access

18Copyright © Prentice Hall 2000 Hard Disks in Groups RAID (Redundant Array of Inexpensive Disks) uses several small hard disks that work together to increase speed and improve reliability.

19Copyright © Prentice Hall 2000 Organizing Data on a Disk There is more than one way to organize data on a disk: Sector methodSector method Cylinder methodCylinder method

20Copyright © Prentice Hall 2000 Sector Method In the sector method, each track on a disk … is divided into sectors that hold a specific number of characters.

21Copyright © Prentice Hall 2000 Cylinder Method Using the cylinder method to organize data on a hard disk, the data is stored vertically within the disk pack.

22Copyright © Prentice Hall 2000 Optical Disks An optical disk consists of a disk with a metallic layer. A laser is used to read/write to an optical disk.

23Copyright © Prentice Hall 2000 Types of Optical Storage Media The various types of optical storage media include: Read-onlyRead-only Write-once/read-manyWrite-once/read-many Magneto-opticalMagneto-optical CD-ROMCD-ROM DVD-ROMDVD-ROM

24Copyright © Prentice Hall 2000 Read-Only These disks can only be read from, not written to. The information stored on dozens of diskettes can be stored on one optical disk. =

25Copyright © Prentice Hall 2000 Write-once/Read-many Often referred to as WORM, after data is written on them, these disks become a read-only medium. WORM disks are ideal for securing original versions of valuable documents and data.

26Copyright © Prentice Hall 2000 Magneto-optical A magneto-optical disk combines the ability to write to disk [magnetic disk feature] with a high volume of storage capacity [optical disk feature].

27Copyright © Prentice Hall 2000 CD-ROM CD-ROM stands for compact disk, read-only memory. A CD-ROM is identical to audio compact disks. Up to 660 MB of storage space is available per disk.

28Copyright © Prentice Hall 2000 DVD-ROM DVD stands for digital video disk. A DVD-ROM can store from 4.7 GB (more than seven times that of a CD-ROM) to 17 GB. Such storage capacity is needed for files containing both text, audio, graphics, and videoin other words, multimedia.

29Copyright © Prentice Hall 2000 Multimedia Multimedia is any combination of: music music animation animation video video text text illustrations illustrations photos photos narration narration

30Copyright © Prentice Hall 2000 Additional Multimedia Requirements CD-ROM drive, sound card, and speakersCD-ROM drive, sound card, and speakers MPEG, if video will be usedMPEG, if video will be used increased RAM capacityincreased RAM capacity high-grade color monitorhigh-grade color monitor vast amounts of secondary storage capacityvast amounts of secondary storage capacity

31Copyright © Prentice Hall 2000 Popular Multimedia Titles With which multimedia titles are you already familiar? ? ? ? ?

32Copyright © Prentice Hall 2000 Magnetic Tape Tape density refers to the stored number of characters (or bytes) per inch. In businesses, magnetic tape is usually reserved for backup purposes.

33Copyright © Prentice Hall 2000 Organizing Stored Data A lot of planning goes into determining how user data will be received, organized, stored, and later, processed by the computer.

34Copyright © Prentice Hall 2000 Data: Getting Organized To be processed by the computer, data is organized into: –Characters –Fields –Records –Files –Databases

35Copyright © Prentice Hall 2000 File Organization There are three major methods of storing files in secondary storage: SequentialSequential DirectDirect IndexedIndexed

36Copyright © Prentice Hall 2000 Sequential File Organization In this method, if a particular record is wanted, all prior records must be read before the desired one is reached. Tape storage is sequential file storage.

37Copyright © Prentice Hall 2000 Direct File Organization In this method of organization, the computer does not have to read all preceding records. Disk storage is an example of direct file organization.

38Copyright © Prentice Hall 2000 Indexed File Organization A compromise between sequential and direct file organization is the indexed method. In this example, records are stored in sequential manner; and the file also contains an indexa directory which speeds up access to desired record.

39Copyright © Prentice Hall 2000 Accessing Stored Data The time needed to access stored data is determined by : Seek timeSeek time Head switchingHead switching Rotational delayRotational delay

40Copyright © Prentice Hall 2000 Seek Time This is the time it takes the access arm to get into position over a particular track. access arm

41Copyright © Prentice Hall 2000 Head Switching Head switching is the activation of a particular read/write head over a particular track on a particular surface.

42Copyright © Prentice Hall 2000 Rotational Delay This is the delay encountered from the time when the access arms and read/write heads are in position until the desired data on the track moves under it.

43Copyright © Prentice Hall 2000 Processing Stored Data There are several techniques for processing stored data: BatchBatch TransactionalTransactional

44Copyright © Prentice Hall 2000 Batch Processing In this technique, transactions are collected into batches and processed at a time when the computer is more accessible.

45Copyright © Prentice Hall 2000 Transaction Processing In this method, transactions are handled immediatelyfast enough for the result to come back and be acted upon right away.

46Copyright © Prentice Hall 2000 Conclusion In the future, storage capabilities will be even greater. This increased storage will benefit law, medicine, science, education, transportation, businesses, the government, and other groups that rely on massive storage of data and quick retrieval.