Storage – holds data, instructions, and information for future use. Every computer uses storage to hold software such as system software and application software. To start up, a computer locates an operating system (system software) in storage and loads it into memory. Users issue commands to start application software, such as word processing or a Web Browser, and the operating system locates the program in storage and loads it into memory. Users store a variety of data and information such as letters, budgets, financial records, e-mail messages, and pictures on computers.

A storage medium, also called secondary storage, is the physical material on which a computer keeps data, instructions, and information. Examples of Storage media are floppy disks, zip disks, hard disks, CDs and DVDs, tape, PC cards, miniature mobile storage media such as memory sticks or cards, USB flash drives, and microfiche.

Capacity is the number of bytes (characters) a storage medium can hold. (See page 350) For example, a typical floppy disk can store up to 1.44 MB of data (1.4 million bytes), and a typical hard disk has 80GB (approximately 80 billion bytes) of storage capacity. Items on a storage medium remain intact even when power is removed from the computer – thus, a storage medium is nonvolatile. Most memory, by contrast, holds data and instructions temporarily and thus is volatile.

Storage Device – is the computer hardware that records and retrieves items to and from storage media. Writing is the process of transferring data, instructions, and information from memory to a storage medium. Reading is the process of transferring these items from a storage medium into memory. The speed of a storage device is defined by access time. Access time measures 1.) the amount of time it takes a storage device to locate an item on a storage medium or 2.) the time required to deliver an item from memory to the processor. The access time of memory devices is measured in nanoseconds (billionths of a second), while the access time of storage devices is measured in milliseconds (thousandths of second). Some manufacturers state a storage device’s transfer rate. Transfer rate is the speed with which data, instructions, and information transfer to and from a device.

Floppy Disks – also called a diskette is a portable, inexpensive storage medium that consists of a thin, circular, flexible plastic Mylar film with a magnetic coating enclosed in a square-shaped plastic shell. A typical floppy disk can store up to 500 double-spaced pages of text, several digital photos, or a small audio file. Users work with floppy disks to transport small files. The 8” floppy disk was introduced in the 1970s by IBM. The next generation of disk was 5.25” wide. Today, the standard floppy disk is 3.5” wide. The floppy disk is portable which means you can remove the disk and use it in other computers.

Floppy Disk Drive – is a device that can read from and write on a floppy disk. Desktop personal computers have a floppy disk drive installed inside the system unit. Some notebook computers have a removable floppy disk drive. Some computers use an external floppy disk drive, in which the drive is a separate device with a cable that plugs into a port on the system unit. (see page 352) Computers with one floppy disk drive refer to it as drive A. Floppy disk drives are downward compatible, which means they recognize and can use earlier media. Floppy drives are not upward compatible, which means they cannot recognize newer media. On the 3.5” floppy disk a piece of metal called the shutter covers an opening in the plastic shell. When you insert the floppy disk into a drive, the drives slides the shutter open. The read/write head is the mechanism in the drive that actually reads items from or writes items on the floppy disk. The average time it takes a current floppy disk drive to locate an item on a disk is 84 milliseconds or 1/12 of a second. Density is the number of bits in an area on a storage medium. A disk with a higher density has more bits in an area and a larger storage capacity

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Characteristics of a Floppy Disk – A floppy disk is a type of magnetic media that allows users to read from and write on a disk any number of times. Magnetic media use magnetic particles to store items such as data, instructions, and information on a disk’s surface. Depending on how the magnetic particles are aligned, they represent either a 0 bit or a 1 bit. A floppy disk stores data in tracks and sectors. A track is a narrow recording band that forms a full circle on the surface of the disk. The disk’s storage locations consist of pie-shaped sections, which break the tracks into small arcs called sectors. A sector stores up to 512 bytes of data. A typical floppy disk stores data on both sides of the disk, has 80 tracks on each side of the recording surface, and has 18 sectors per track. (See page 353) For reading and writing purposes, sectors are grouped into clusters. A cluster is the smallest unit of disk space that stores data. Each cluster consists of two to eight sectors. Even if a file consists of only a few bytes, it uses an entire cluster. Each cluster holds data from only one file. One file, however, can span many clusters. Before you can write on a new floppy disk, it must be formatted. Formatting is the process of preparing a disk for reading and writing by organizing the disk into storage locations called tracks and sectors.

Care of Floppy Disks – Disk manufacturers state that a floppy disk can last at least seven years, with reasonable care. In many cases, the disks do not have that long of a life span. Frequently, disks are damaged from improper care. When handling a floppy disk, you should avoid exposing it to heat, cold, magnetic fields, magnets, and contaminants such as dust, smoke, or salt air. Exposure to these elements could damage or destroy the data on the disk. To prevent files from accidentally being erased, floppy disks have a write-protect notch. If the write-protect notch is closed the drive can write on the floppy disk. If the write-protect notch is open, the drive cannot write on the floppy disk. Some floppy disks have a second opening on the opposite side of the disk that does not have the small tab. This opening identifies the disk as a HD floppy disk.

Zip Disks – A Zip disk is a type of portable magnetic media that can store from 100 MB to 750 MB of data. The larger capacity Zip disks hold about 500 times more than a standard floppy disk. These large capacities make it easy to transport many files or large items such as graphics, audio, or video files. Another popular use of Zip disks is to back up important data and information. A backup is a duplicate of a file, program, or disk that can be used if the original is lost, damaged or destroyed. Zip disks are larger than and about twice as thick as a 3.5-inch floppy disk. A Zip drive is a high-capacity disk drive developed by Iomega Corporation that reads from and writes on a Zip disk. These drives cannot read standard 3.5-inch floppy disks. You can purchase an external Zip drive, which connects to a USB port, FireWire port, or parallel port on the system unit.

Hard Disk, also called hard disk drive, is a storage device that contains one or more inflexible, circular platters that store data, instructions, and information. The system unit on most desktop and notebook computers contains at least one hard disk. The hard disk inside the system unit is called a fixed disk because it is placed in a drive bay and usually is not portable. The entire device is enclosed in an airtight, sealed case to protect it from contamination. Current personal computer hard disks have storage capacities from 40 to 250 GB and more. Hard disks store data magnetically. A recently developed hard disk, called an optically assisted hard drive, combines optic technologies with the magnetic media. These optically assisted hard drives have potential storage capacities up to 400 GB. If the computer contains only one hard disk, the operating system designates it as drive C.

Characteristics of a Hard Disk – The capacity of a hard disk is determined from the number of platters it contains, together with composition of the magnetic coating on the platters. A platter is made of aluminum glass, or ceramic and is coated with an alloy material that allows items to be recorded magnetically on its surface. A typical hard disk has multiple platters, and each platter has two read/write heads, one for each side. (See page 357) While the computer is running, the platters in the hard disk rotate at a high rate of speed. This spinning (5,400 to 7.200 revolution s per minute) allows nearly instant access to all tracks and

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sectors on the platters. The platters continue to spin until power is removed from the computer. On some computers, the hard disk stops spinning after a specified time to save power. The read/write head floats above the platter instead of making contact with the platter surface. The distance between the read/write head and the platter is about two millionths of one inch. This close clearance leaves no room for any type of contamination. Dirt, hairs, dust, smoke, and other particles could cause the hard disk to have a head crash. A head crash occurs when a read/write head touches the surface of a platter, usually resulting in a loss of data or sometimes loss of the entire drive. Although current internal hard disks are built to withstand shocks and are sealed tightly to keep out contaminants, head crashes do occasionally still occur. Therefore, you should back up your hard disk regularly. Access time for today’s hard disks ranges from 4 to 12 ms. (milliseconds) The average hard disk access time is at least seven times faster than the average floppy disk drive. The hard disk spins constantly, while a sloppy disk starts spinning only when it receives a read or write command. Some computers improve hard disk access time by using disk cashing. Disk Cache is a portion of memory that the processor uses to store frequently accessed items. A cache controller manages cache and thus determines which items cache should store.

External and Removable Hard Disks – Two types of portable hard disks are external hard disks and removable hard disks. An external hard disk is a separate free-standing hard disk that connects with a cable to a USB port, FireWire Port, or other port on the system unit. External hard disks have storage capacities up to 250 GB or higher. A removable hard disk is a hard disk that you insert and remove from the hard disk drive. Sometimes the hard disk drive is built into the system unit. Others are external devices that connect with a cable to a USB port, FireWire port, or other port. Removable hard disks have storage capacities up to 80 GB or higher. (See page 359) A disk controller consists of a special-purpose chip and electronic circuits that control the transfer of data from a disk to and from the system bus. EIDE is one of the more widely used controllers for hard disks. EIDE (Enhanced Integrated Drive Electronics) controllers can support up to four hard disks and provide connections for CD and DVD drives and tape drives. A SCSI (Small Computer System Interface) controller can support up to either or fifteen peripheral devices, including hard disks, CD and DVD drives, tape drives printers, scanners, network chards, and much more . Maintaining Data Stored on a Hard Disk -- Most manufacturers guarantee their hard disks to last approximately three to five years. Many last much longer with proper care. To prevent the loss of items stored on a hard disk, you should perform preventive maintenance such as defragmenting or scanning the disk for errors.

Internet Hard Drives – Instead of storing data locally on a hard disk, some users choose to store data on an Internet hard drive. An Internet hard drive, sometimes called online storage, is a service on the Web that provides storage to computer users, usually for a minimal monthly fee. For example, one online storage service charge is for $4.99 per month for 100 MG of storage. In addition to storage space these Web sites often offer services such as e-mail and calendars.

CDs and DVDs are a type of optical storage media that consists of a flat, round, portable disc made of metal, plastic, and lacquer. CDs and DVDs primarily store software, data, digital photos, movies, and music. Some CD and DVD formats are read only, meaning you cannot write (save) on the media. Just about every personal computer today includes some type of CD or DVD drive installed in a drive bay. These drives read CDs and DVDs, and in many cases, will play audio CDs. CDs and DVDs are optical media and store information by using microscopic pits (indentations) and lands (flat areas) that are in the middle layer of the disc. Most manufacturers place a silk-screened label on the top layer of the disc. A high-powered laser light creates the pits. A lower-powered laser light reads items from the disc by reflecting light through the bottom of the disc, which usually is either solid gold or silver in color. The reflected light is converted into a series of bits the computer can process. A land causes light to reflect, which is read as binary digit 1. Pits absorb the light; this absence of light is read as binary digit 0. CDs and DVDs store items in a single track that spirals from the center of the disc to the edge of the disc. (See page 362)

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Care of CDs and DVDs – Manufacturers guarantee that a properly cared for CD or DVD will last 5 years, but could last up to 100 years. If a disc becomes warped or if its surface is scratched, data on the disc may be unreadable. Exposing these discs to extreme temperatures or humidity could cause them to warp. Place a CD or DVD in its protective case, called a jewel box, when you are finished using it. (See page 363)

CD-ROMS or compact disc read-only memory is a type of optical disc that uses laser technology to store data, instructions, and information. In addition to audio, a CD-ROM can contain text, graphics, and video. Manufacturers write, or record, the contents of standard CD-ROMs. Users can read only the contents of these discs. Users cannot erase or modify the contents. A standard CD-ROM is called a single-session disk because manufacturers write all items on the disc at one time. Because audio CDs and CD-ROMs use the same laser technology, you may be able to use a CD-ROM drive to listen to an audio CD. Some music companies, however, configure their CDs so the music will not play on a computer. They do this to protect themselves from customers illegally copying and sharing the music.

A typical CD-RM holds from 650 MB to 1 GB of data. This is equivalent to about 450 high-density 3.5-inch floppy disks. Manufacturers use CD-ROMS to store today’s multimedia and other complex software. The speed of a CD-ROM drive determines how fast it installs programs and accesses the disc. Original CD-ROM drives were single-speed rives with transfer rates of 150 KBps. (kilobytes per second) Manufacturers measure all CD-ROM drives relative to the original drive. They use X to denote the original transfer rate of 150 KBps. For example, a 48X CD-ROM drive has a data transfer rate of 7,200 (48 X 150) KBps, or 7.2 MBps. Current CD-ROM drives have transfer rates ranging from 48X to 75X or faster. Faster CD-ROM drives are more expensive than slower drives.

Picture CDs and Photo CDs -- A Kodak Picture CD is a type of compact disc that stores digital versions of a single roll of film using a jpg file format. A standard CD-ROM drive can read a Picture CD. Using photo editing software and the photos on the Picture CD, you can remove red eye, crop the photo, enhance colors, trim edges, and adjust lighting. Another type of compact disc that stores digital photos is the Photo CD. A single Photo CD stores images from multiple rolls of film using the Image Pac or PCD file format, which was developed by Eastman Kodak. The Photo CD was designed for commercial professional users. A Photo CD is a multi-session disc, which means users can save additional photos on the disc at a later time.

CD-Rs and CD-RWs -- With a CD-R or a CD-RW drive, users can record or write their own data onto a disc. The process of writing on an optical disc is called burning. Some operating systems, such as Windows XP, include the capability of burning discs. A CD-R (Compact disc-recordable) is a multi-session CD onto which users record their own items such as text, graphics, and audio. With a CD-R, you can write on part of the disc at one time and another part at a later time. Each part of A CD-R can be written on only one time, and the disc’s contents cannot be erased. Most current CD-ROM drives can read a CD-R. Writing on a CD-R requires a CD-R drive. A CD-R drive usually can read both audio CDs and standard CD-ROMs. These drives read at speeds of 48X or more and write at speeds of 40X or more. Manufacturers often list the write speed first, such as 40/48.

Instead of using a CD-R drive, many users opt for a CD-RW drive. A CD-RW is an erasable disc you can write on multiple times. With CD-RW, the disc allows users to write and rewrite data onto it multiple times. Reliability of the disc tends to drop with each successive rewrite. To write on a CD-RW disc, you must have CD-RW software and a CD-RW drive. These drives have write speeds of 52X or more, and rewrite speeds of 24X or more, and read speeds of 52X or more. Manufacturers state the speeds in this order: write speed, rewrite speed, and read speed: 52/24/52. Multiread CD drives are the only drives that can read CD-RW discs. A multiread CD drive is a drive that reads audio CDs, data CDs, CD-Rs, and CD-RWs. Most current CD drives are multiread. A popular use of CD-RW and CD-R discs is to create audio CDs. Users can record their own music and save it on a CD, purchase and download MP3 songs from the Web, or

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rearrange tracks on a purchased music CD. The process of copying an individual song from a purchased audio CD and converting it to a digital format is called ripping. (See page 367) It is legal to copy songs from an audio CD that you obtained legally, if you use the copied music for your own personal use. If you share the copy with a friend, you are violating copyright law. It is legal to download copyrighted music if the song’s copyright holder has granted permission for users to download and play the song. In most cases, you pay a fee for the song.

DVD-ROMs (Digital Versatile Disc-ROM or digital video disc-ROM) is an extremely high-capacity optical disc capable of storing from 4.7 GB to 17 GB. The storage capacity of a DVD-ROM is more than enough to hold a telephone book containing every resident in the United States. The capacity of a DVD-ROM is greater than that of a CD-ROM, and the DVD-ROM’s quality far surpasses that of the CD-Rom because images are stored at higher resolution. The goal of DVD technology is to meet the needs of home entertainment, computer usage, and business data and information storage with a single medium. When you rent or buy a DVD movie, it uses the DVD-video format to store motion pictures digitally. To read a DVD-ROM, you must have a DVD-ROM drive or DVD player. These drives can read at speeds of 48X or more. Newer DVD-ROM drives also can read audio CDs, CD-ROMS, CD-Rs, and CD-RWs. Manufacturers advertise this multifunctional drive as a CD-RW/DVD. A DVD-ROM uses one of three storage techniques. The first involves making the disc denser by packing the pits closer together. The second involves using two layers of pits. For this technique, the lower layer of pits is semitransparent so the laser can read through it to the upper layer. This technique doubles the capacity of the disc. Also, some DVD-ROMs are double-sided, which means you must remove the DVD-ROM and turn it over to read the other side. (See page 369)

DVD+RW and other DVD Variations – DVDs are available in a variety of formats. To view a DVD movie on a computer screen insert the DVD movie into a DVD-ROM drive. When music is stored on a DVD, it includes surround sound and has a much better quality than that of an audio CD. DVD-R (DVD-recordable) allows user to write on the disc once and read it many times. With DVD-RW and DVD+RW (DVD-rewriteable) discs, a user can erase and record more than 1,000 times. DVD-RW and DVD+RW have storage capacities up to 4.7 GB per side. These drives have rewrite speeds of 12X ore more, and read speeds of 32X ore more. The drives usually can read DVD-ROM, DVD-R, and all CD media, and they can write on DVD-RW, or DVD+RW, or DVD-R, CD-R, and CD-RW media. To write on DVD+RW discs, you must have a DVD-RW drive, DVD+RW drive, or a DVD writer. DVD+RAM (DVD + random access memory) allows users to erase and record on a DVD+RAM disc more than 100,000 times. DVD+RAM discs have storage capacities up to 4.7 GB per side. These discs can be read by DVD+RAM drives and some DVD-ROM drives and players. As the cost of DVD technologies becomes more reasonable, many industry professionals expect that DVD eventually will replace all CD media.

Tapes – One of the first storage media used with mainframe computers was magnetic tape – a magnetically coated ribbon of plastic capable of storing large amounts of data and information at a low cost. Similar to a tape recorder, a tape drive reads from and writes data and information on a tape. Today’s tape drives use tape cartridges. Businesses and home users sometimes back up personal computer hard disks onto tape. Some personal computers have external tape units. Tape storage requires sequential access, which refers to reading or writing data consecutively. Like a music tape, you must forward or rewind the tape to get to a specific point. Floppy disk, hard disk, and compact discs all use direct access. Direct access or random access, means the device can locate a particular data item or file immediately, without having to move consecutively through items stored in front of it. Sequential access is much slower than direct access. For this reason, tapes are no longer used as a primary method of storage. Tapes are used for long-term storage or backup.

PC Card – is a thin, credit card-sized device that fits into a PC Card slot. PC Cards are most often used with laptop or notebook computers. Different types and sizes of PC Cards add storage, additional memory,

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fax/modem, networking, sound, and other capabilities. They are available in three kinds: Type I, Type II, and Type III. Some digital cameras use Type II or Type III PC Card to store photos. PC Cards that house a hard disk have storage capacities up to 5 GB. Type I cards are used to add memory. Type II cards are used to add modems, networking, sounds, hard disks and Type III cards are used to house hard disks. (See page 370)

Miniature Mobile Storage Media allow mobile users easily to transport digital images, music, or documents to and from computers and other devices. Today, many desktop computers, notebook computers, Tablet PCs, PDAs, digital cameras, music players, and smart phones have ports or slots to hold miniature mobile storage media. Many types of miniature mobile storage media are available with capacities ranging from 16 MB to 4 GB. (See page 372) Common types of miniature storage media include Compact Flash, Smart Media, Memory Stick and Microdrive.

Flash memory cards are sometimes called solid-state devices, which means they consist entirely of electronics (chips, wires, etc) and contain no moving parts. Miniature hard disks are magnetic media and operate like their desktop-sized counterparts – just on a smaller scale. Manufacturers claim miniature mobile storage media can last from 10 to 100 years. Minature storage media are much smaller, lighter in weight, and more portable than other storage media such as hard disks. They are however, much more expensive. If your computer or printer does not have a built-in slot, card read/writer are available. A card reader/writer is a device that reads and writes data, stored on PC Card or memory cards. Card reader/ writers usually connect to the USB port, Fire Wire port, or parallel port. A USB Flash drive, sometimes called a key chain drive, is a flash memory storage device that plugs into a USB port on a computer or portable device. Current USB flash drives have storage capacities of up to 2 GB. Experts predict that USB flash drives will become the mobile user’s primary storage device eventually making the floppy disk obsolete because they have mush greater storage capacities.

Smart Cards – is similar in size to a credit card and it stores data on a thin microprocessor embedded in the card. (See page 373) The intelligent smart card contains a CPU and has input, process, output, and storage capabilities. These cards are referred to as intelligent smart cards to differentiate them from a flash memory card, which has only storage capabilities. You need a specialized card read to read the information stored on a smart card. Smart cards can store a prepaid dollar amount as with a prepaid telephone calling card. There is a specific dollar amount stored in the microprocessor. Each time you use the card, the available amount of money is reduced. Other uses of smart cards include storing patient records, vaccination data and other health care information. Electronic money (e-money) or digital cash is a means of paying for goods and services over the Internet. A bank issues unique digital cash numbers that represent an amount of money. The amount of the money is withdrawn from your bank account. To use the card, you swipe it through a card reader on your computer or one that is attached to your computer. Microfilm and Microfiche – store microscopic images of documents on roll or sheet film. A computer output microfilm recorder is the device that records the images on the film. The stored images are so small that you can only read them with a special reader. Libraries use these media to store back issues of newspapers and magazines. Large organizations use microfilm and microfiche to archive inactive files. These storage methods are inexpensive and have the longest life of any storage media.Enterprise Storage – A large business, commonly referred to as an enterprise, has hundreds or thousands of employees in offices across the country. Enterprises use computers and computer networks to manage and store huge volumes of data. To meet their large-scale needs, enterprises use special hardware geared for maximum availability and efficiency. One or more servers on the network have the sole purpose of providing storage to connected users.

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