Presentations by: Fred Bounds Timothy J. O’Leary Linda I. O’Leary COMPUTING ESSENTIALS 1999 2000 1999 Presentations by: Fred Bounds 2000

5 CHAPTER Secondary Storage

Computing Essentials 1999 - 2000 Chapter Five Competencies After reading this chapter, you should be able to: 1. Describe today’s standard floppy disk and compare it to Zip, SuperDisks and HiFD disks. 2. Describe the following kinds of disks: internal hard disks, hard-disk cartridges and hard-disk packs. Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Competencies 3. Describe ways to improve hard-disk operations: disk caching, redundant arrays of inexpensive disks and data compression. 4. Compare the CD and DVD optical disk formats. Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Competencies 5. Describe the different types of optical disks. 6. Describe magnetic tape streamers and magnetic tape reels. Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Overview Computers permanently save information For future use To share information with others To modify information already available Stores programs and data As opposed to temporary storage (RAM), which is volatile, secondary storage is nonvolatile Computing Essentials 1999 - 2000 Chapter Five

Floppy Disks Floppy disks are removable storage media. Today’s standard is 1.44 MB. Tomorrow’s might be a Zip, SuperDisk or HiFD. Data is recorded on tracks and sectors.

Computing Essentials 1999 - 2000 Chapter Five Floppy Disks Removable storage media inserted into disk drives Flat circular pieces of mylar plastic rotating within a jacket The bits of data are represented by the presence or absence of magnetic charges Computing Essentials 1999 - 2000 Chapter Five

Floppy Disks - Today’s Standard Storage capacities range from 360 KB to 1.44 MB Jackets covering the mylar disk can be flexible or sturdy Write-protect notch or window to prevent inadvertent erasure or write-over Computing Essentials 1999 - 2000 Chapter Five

Floppy Disks - Tomorrow’s Standard Zip Disks 100 MB capacity (70 times regular floppy) Becoming standard feature on new systems May be the next floppy disk standard SuperDisks 120 MB capacity Can read and write standard floppies, while Zips cannot Computing Essentials 1999 - 2000 Chapter Five

Floppy Disks - Tomorrow’s Standard HiFD disks 200 MB capacity (140 times standard floppy) Can also read and write standard floppies Computing Essentials 1999 - 2000 Chapter Five

The Parts of a Floppy Disk Data recorded in rings called called tracks Tracks divided into wedge-shaped sections called sectors Most disks manufactured without tracks and sectors and must have “soft sectors” added through the formatting process Computing Essentials 1999 - 2000 Chapter Five

Typical Floppy Disk Capacities 2HD 1.44 MB SuperDisk 120 MB Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five How a Disk Drive Works Drive motor turns mylar disk Access arm moves read-write heads back and forth Read-write heads then read or write on the disk surface read-write head access arm 3 1/2-inch floppy disk tracks (invisible) Computing Essentials 1999 - 2000 Chapter Five

Hard Disks Hard disks are of three types: internal hard disk, hard-disk cartridge and hard-disk pack.

Computing Essentials 1999 - 2000 Chapter Five Hard Disks Composed of metallic rather than plastic disks Fast information storage and retrieval Read-write heads “fly” over the disk surface on a cushion of extremely thin air Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Hard Disks A smoke particle, human hair or fingerprint could cause a head crash Head crashes occur when the read-write head contacts the disk surface Computing Essentials 1999 - 2000 Chapter Five

Materials that can cause a head crash Computing Essentials 1999 - 2000 Chapter Five

Materials that can cause a head crash dust particle human hair fingerprint smoke particle Materials that can cause a head crash Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Internal Hard Disk Located inside the system unit Also known as fixed disk For storing the operating system, other programs and large data files Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Internal Hard Disk One or more metallic platters sealed inside a container Container holds Motor for rotating the disks Access arm and read-write heads Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Internal Hard Disk Advantages over floppy disks Capacity (up to thousands times a single floppy Speed (ten times the speed) Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Hard-Disk Cartridges Hard disk can be easily removed Give microcomputer fast access to large amounts of data Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Hard-Disk Cartridges Complements internal hard disk Typical capacity, 2 GB Popular vendors: Iomega and SyQuest Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Hard-Disk Packs Removable, massive storage capacity Common in mainframe systems Composed of a larger number of platters, resembling a stack of record albums Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Hard-Disk Packs Most platters offer read-write surfaces on top and bottom Used with larger computer systems Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Hard-Disk Packs Access time - time between the computer’s request for data from secondary storage and the completion of the data transfer Computing Essentials 1999 - 2000 Chapter Five

Performance Enhancements Disk caching Uses hardware and software to anticipate data needs Frequently used data is stored in memory, when needed, the access time is much faster Computing Essentials 1999 - 2000 Chapter Five

Performance Enhancements Redundant arrays of inexpensive disks (RAID) Groups of low cost hard-disk drives grouped together using networks and special software Performs as a single large-capacity disk But faster than a single disk of comparable size Computing Essentials 1999 - 2000 Chapter Five

Performance Enhancements File compression and decompression Increase storage capacity Reduce space required for storage Aids in file transmission WinZip and PKZip are well-known programs Computing Essentials 1999 - 2000 Chapter Five

Optical Disks Optical disks use laser technology. CD and DVD are optical disk formats.

Computing Essentials 1999 - 2000 Chapter Five Optical Disks Compact, high capacity form of permanent storage Laser beam writes by creating a pattern of pits (holes) and lands (flat areas) to encode data bits Laser beams reflect off the pits and lands to read the data Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Optical Disks Up to 4.7 gigabytes of data Equivalent of over 1 million typewritten pages Three types of optical discs CD-ROM, CD-R and erasable optical discs, or CD-RW Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five CD-ROM Stands for compact disc-read-only memory Can be read from, but not written to Can hold up to 650 MB of information Grolier Electronic Encyclopedia - nine million words and 1900 pictures Used to distribute large software packages Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five CD-ROM drive CD-ROM How a CD-ROM works CD-ROM carrying case Reflected light Laser beam Reflecting surface Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five CD-R Stands for CD-Recordable Also known as WORM, or write once, read many Ideal for use as permanent data archives for essential company information CD changers or CD jukeboxes can facilitate rapid access to large amounts of information Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five CD-RW Also known as rewritable optical discs Unlike CD-R, these discs can be written on numerous times Most common technology is magneto-optical (MO) disc drive, combining magnetic and optical technologies Capacities up to 1,000 megabytes (a gigabyte) Computing Essentials 1999 - 2000 Chapter Five

Digital Versatile Disk Commonly known as digital video disk or DVD Up to 4.7 gigabytes capacity, seven times CD With two-sided storage, 17 gigabytes out soon Predicted to replace CD as a standard Computing Essentials 1999 - 2000 Chapter Five

Digital Versatile Disk DVD-ROM - provide high quality, movie length videos DVD-R - consumer recordable version just getting started DVD-RAM or DVD-RW - rewritable version Computing Essentials 1999 - 2000 Chapter Five

Magnetic Tape Magnetic tape streamers and magnetic tape reels are used primarily for backup purposes.

Computing Essentials 1999 - 2000 Chapter Five Magnetic Tape Disks offer fast, direct access to data programs Tapes are sequential access, because they have to be fast forwarded or rewound before a specific location can be reached Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Magnetic Tape A common sequential access method of permanent storage method A common form of data backup in companies with larger computer systems Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Magnetic Tape Two forms of tape storage Magnetic tape streamers Magnetic tape reels Computing Essentials 1999 - 2000 Chapter Five

Magnetic Tape Streamers Backup tape cartridge units used with microcomputer systems Typical capacities range from 120 MB to 5 GB Advanced forms use digital audio tape (DAT) Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Magnetic Tape Reels Used with minicomputer and mainframe computers Often 1/2 inch wide and 1/2 mile long Stores 1600 to 6400 characters per inch Tapes are run on magnetic tape drives or magnetic tape units Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Magnetic Tape Reels Used with minicomputer and mainframe computers Often 1/2 inch wide and 1/2 mile long Stores 1600 to 6400 characters per inch Tapes are run on magnetic tape drives or magnetic tape units Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five Magnetic Tape Reels Take-up reel Supply reel Read-write head Erase head Tape Computing Essentials 1999 - 2000 Chapter Five

Computing Essentials 1999 - 2000 Chapter Five