Secondary storage permanently saves information for future use; to share information with others; to modify at later date Secondary storage is nonvolatile – stores programs and data as opposed to temporary storage (RAM) Characteristics include: Media or medium – actual physical materials that holds the data and programs Capacity – measures how much a particular storage medium can hold Storage devices – hardware that reads data and programs from storage media (most also write to storage media) Access speed or access time – measures the amount of time required by the storage device to retrieve data and programs Writing– process of saving information to the secondary storage device Reading – process of accessing information from secondary storage
Floppy disk – inexpensive and removable Optical disks – large storage capacity (Key Term) Hard disk – large storage capacity and fast retrieval times
Floppy disks are removable storage media. Today’s standard is 1.44 MB 3 ½-inch disk (Key Term) . Data recorded in rings called called tracks; tracks divided into wedge-shaped sections called sectors Most disks (Key Term) manufactured currently preformatted w/tracks and sectors While called floppy, actually pieces of flat Mylar rotating within a hard plastic jacket The bits of data are represented by the presence or absence of magnetic charges Storage capacities range from 360 KB to 1.44 MB Write-protect notch or window to prevent inadvertent erasure or write-over Density (Key Term) refers to how tightly the bits can be packed next to one another; common density is 2HD A shutter on the disk slides to the side to expose the recording surface Labels provide an area to write or document the contents of the disk
Floppy-disk cartridge can also be referred to as a high-capacity disk (Key Term) Zip disks – usually manufactured by Iomega; 100 MB, 250 MB, or 750 MB worth of storage; requires own drive HiDF disks – usually manufactured by Sony Corp; 200 MB or 750 MB capacity Biggest advantages: can use HiDF disk in floppy drive; popular with notebooks Super disks – usually manufactured by Imation; 120 MB or 240 MB capacity; SuperDisk disk drives can use standard floppy disks Zip disks – 100 MB, 250 MB or 750 MB HiFD disks - 200MB or 720MB SuperDisks – 120 MB or 240 MB
Composed of metallic rather than plastic disks Platters – rigid metallic, stacked one on top of another A cylinder (Key Term) runs through each track of a stack of platters Fast information storage and retrieval Read-write head is .000001 inch above surface
Head crashes occur when the read-write head contacts with the disk surface or with particles on the disk's surface Head crashes are now rare A smoke particle, human hair, or fingerprint could cause a head crash
Located inside the system unit Used for storing the operating system, other programs, and large data files You should perform routine maintenance and periodically backup all important files
Capacity limited only by number of cartridges; used to complement internal hard disk. PC Card hard disk (Key Term) available for notebooks with a capacity of up to 5 GB
Massive storage capacity Common in mainframe systems Composed of a larger number of platters, resembling a stack of record albums Most platters offer read-write surfaces on top and bottom Access time – time between the computer’s request for data from secondary storage and the completion of the data transfer; usually access time is faster with this type of secondary storage
Disk caching Uses hardware and software to anticipate data needs; performs function similar to RAM caching; improves processing by acting as a temporary high-speed holding area between a secondary storage device (Key Term) and the CPU Frequently used data is stored in memory; when needed, the access time is much faster 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 Often used by Internet servers and large organizations File compression and decompression Increase storage capacity Reduce space required for storage; reduce up to ¼ of original size WinZip and PKZip are well-known programs, and you can also use utility programs in Windows XP
Use laser technology. CD (Key Term) and DVD (Key Term) are optical disk formats. Compact, high capacity form of permanent storage (up to 50 gigabytes of data) Optical discs are read by an optical disc drive 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 Rotational speed determines how fast data can be transferred from the CD Optical disks come in many different sizes Most common is 4 ¾ inches Stored in a protective case called jewel boxes
CD stands for compact disc Standard on most computers; can store from 650 MB up to 1 GB Speed determines how fast data can be transferred Read only: CD-ROM Commercial music CD Read only means it cannot be written on or erased Used to distribute large databases and references Write once: CD-R (CD-recordable) Used to archive data or to record music downloaded from the Internet Rewriteable: CD-RW Known as erasable optical disks (Key Term) Can be changed Used to create and edit multimedia presentations Ideal for use as permanent data archives for essential company information
DVD-ROM Known as DVD players (Key Term) Used for videos DVD-R and DVD+R Two competing write once formats Write once format Used to create permanent archives for large amounts of data and to record videos DVD-RAM or DVD-RW – rewritable version DVD-RW DVD+RW DVD-RAM Each format has a unique way of storing data; older DVD players can’t read all formats but the new DVD players can Rapidly replacing the CD rewritable drives Use to store video from camcorders and developing large multimedia presentations that include extensive graphics and video
HD DVD stands for high definition DVD Capacity of 15 to 45 gigabytes Advantage is that current manufacturing plants producing standard DVD discs can be easily converted to mass produce HD DVD discs Blu-Ray, also known as BDs Have a capacity of 25 to 50 gigabytes Cannot be easily manufactured in existing DVD disc manufacturing plants The two formats appear that they will not be compatible with each other
Solid-state storage No moving parts Reliable, but expensive Requires less power Internet hard drives (Key Term) Low cost Flexibility to access information from any location using the Internet Slower access speed Magnetic tape Slower sequential access (Key Term) Stores data and programs Used for making backups of data
Flash memory cards are one type of solid state device. USB drives (Key Term) provide very compact space Key chain hard drives have recently been introduced Very compact Worn as a necklace or on a key ring Connect to a USB port Predicted that they will replace the floppy disk for transporting data Capacities up to 2 GB
These are Web sites that provide storage space Not used for storing highly personalized or sensitive information
Sequential access because they have to be fast forwarded or rewound before a specific location can be reached A common sequential access method of permanent storage method Common form of data backup in companies with larger computer systems; magnetic disk offer fast, direct access to data programs Two forms of tape storage Magnetic tape streamers Backup tape cartridge units used with microcomputer systems Capacities range from 120 MB to 5 GB At one time, mainframe computers used magnetic tape reels (Key Term) exclusively
Mass storage devices that support enterprise storage systems are File servers (Key Term) – dedicated computer with very large storage capacities that provide user access to fast storage and retrieval of data RAID systems (Key Term) – larger versions of the specialized devices discussed earlier in this chapter that enhance organizational security by constantly making backup copies of files moving across the organization’s networks Tape library (Key Term) – device that provides automatic access to data archived on a large collection or library of tapes DVD-ROM and CD-ROM jukeboxes (Key Term) – provide automatic access to a large collection or library of optical disks Organizational Internet Storage (Key Term) – high-speed Internet connection to a dedicated remote organizational Internet drive site
Are there downsides? Could your personal video log be used to incriminate you in a court of law? Could someone else’s video log be an invasion of your right to privacy?
Have students turn to the end of Chapter 8 in their textbooks to view the same “Open-Ended” questions/statements
Have students turn to the end of Chapter 8 in their textbooks to view the same “Open-Ended” questions/statements
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