Computer Chapter 7

Storage
Location in which data, instructions, and information are held for future use.
Start up
a computer locates an operating system (system software) in storage, usually a hard disk, and loads it into memory (RAM). When a user issues a command to start application software, the operating system locates the program in storage and loads it into memory (RAM).
storage medium
also called secondary storage, the physical material on which a computer keeps data, instructions, and information. Is nonvolatile, items on it remain intact when power is off.
Memory (RAM)
consists of one or more chips on the motherboard or some other circuit board in the computer. Is volatile, holds data temporarily.
capacity
Number of bytes a storage medium can hold.
storage device
Hardware used to record (write and/or read) items to and from storage media.
writing
Process of transferring data, instructions, and information from memory to a storage medium.
reading
Process of transferring data, instructions, and information from a storage medium into memory.
access time
is the speed of stage devices and memory. Measurement of the amount of time it takes the process to read data, instructions, and information from memory. It measures: [1] the amount of time it takes a storage device to locate an time on a storage medium or [2] the time required to deliver an item form memory to processor. The access time of storage devices is slow (milli/microsecond) compared to memory (nanosecond).
Transfer rate
The speed at which data, instructions, and information transfer to and from a device. Transfer rate for storage are KBps (kilobytes per second), GBps, & GBsp.
Hard disk
Type of storage device that contains one or more inflexible, circular platters that use magnetic particles to store data, instructions, and information. Are read/write storage media. Access time ranges from about 3 to 12 ms-milliseconds.
fixed disk
Name sometimes given to the hard disk mounted inside a system unit.
portable disk
The capability of a storage medium to be removed from one computer and carried to another computer.
longitudinal recording
Storage technique in which magnetic particles are aligned horizontally around the surface of the disk.
perpendicular recording
Storage technique in which magnetic particles are aligned vertically, or perpendicular to the disk’s surface, making much greater storage capacities possible.
platter
Component of a hard disk that is made of aluminum, glass, or ceramic and is coated with an alloy material that allows items to be recorded magnetically on its surface.
formatting
Process of dividing a disk into tracks and sectors so the operating system can store and locate data and information on the disk.
track
Narrow recording band that forms a full circle on the surface of a disk.
sectors
The small arcs into which tracks on a disk are divided.
clusters
Smallest unit of disk space that stores data and information. See also allocation unit.
allocation unit
Smallest unit of disk space that stores data and information. Also called a cluster.
form factor
Term that refers to the size of platters in a hard disk.
read/write head
Mechanism in a disk drive that reads items or writes items as it barely touches the disk’s recording surface.
cylinder
The vertical section of a hard disk track that passes through all platters. A single movement of the read/write head arms accesses all the platters in a cylinder.
revolution per minute (rpm)
The number of times per minute that a hard disk platter rotates. The spinning motion is creates a cushion of air between the platter and its read/write head; distance about two millionths of one inch.
head crash
Type of hard disk failure that occurs when a read/write head touches the surface of a platter.
backup
Duplicate of a file, program, or disk placed on a separate storage medium that can be used if the original is lost, damaged, or destroyed.
disk cache
Memory chips on a hard disk that store frequently accessed items such as data, instructions, and information. Hard disk contain between 2MB and 64MB of disk cache.
density
Number of bits in an area on a storage medium. Higher density means more storage capacity.
RAID (redundant array of independent disks)
group of two or more integrated hard disks.
NAS (network attached storage)
Server connected to a network with the sole purpose of providing storage.
external hard disk
Separate freestanding hard disk that connects with a cable to a USB port or FireWire port on the system unit. Storage capacity up to 4TB.
removable hard disk
Process of transferring data, instructions, and information from a storage medium into memory.
pocket hard drive
Term that refers to smaller external hard disks because they enable users easily to transport photos and other files from one computer to another. Miniature hard disk have storage capacity that range from 1 GB to 320GB and usually perpendicular recording.
disk controller
Special-purpose chip and electronic circuits that control the transfer of data, instructions, and information between a disk and the system bus and other components in a computer.
SATA (Serial Advanced Technology Attachment)
Hard disk interface that uses serial signals to transfer data, instructions, and information and has transfer rates of up to 300 MBps and higher. Advantage is that their cables are thinner, longer, more flexible, and less susceptible to interference than cables used by hard disks that use parellel signals. Transfer rate up to 300MBps.
eSATA (external SATA)
hard disk interface that is much faster than USB and FireWire.
EIDE (Enhanced Integrated Drive Electronics)
Interface that uses parallel signals to transfer data, instructions, and information and can support up to 4 hard disks at 137 GB per disk. Transfer rate up to 133MBps.
SCSI (Small computer system interface)
use parallel signals, can support up to 8 or 15 peripheral devices. Supported devices include hard disk, optical disc drives, tap drives, printers, scanners, and network cards. Transfer rate up to 640 MBps.
SAS (serial-attached SCSI)
Newer type of SCSI that uses serial signals to transfer data, instructions, and information. Advantage over SCSI include thinner, longer cables; reduced interference, less expensive, and supports many more connected devices at once. Transfer rate 750 MBps.compatible with devices that have parallel SCSI and SATA interfaces. Experts predict that SAS will replace parallel SCSI.
solid state media
refer to components that consist entirely of electronic components, such as integrated circuits, and contain no moving parts.
solid state drives (SSD)
Storage device that typically uses flash memory to store data, instructions, and information. Disadvantage is higher failure rate than hard disks.
memory card
Removable flash memory device, usually no bigger than 1.5″ in height or width, that you insert and remove from a slot in a personal computer, game console, mobile device, or card reader/writer. Can last from 10 to 100 years. Transfer rate ranges form 1MBps to 20MBps.
card reader/writer
Device that reads and writes data, instructions, and information stored on flash memory cards.
USB flash drive
also called thumb drive, flash memory storage device that plugs in a USB port on a computer or portable device. The drive designation of a USB flash drive follows alphabetically after all other disks.
smart drive
a special type of USB flash drive including pre-installed software accessed through a Window’s type interface.
ExpressCard module
removable flash memory device, about 75mm long and 34mm wide or L-shaped with a width of 54mm, that fits in an ExpressCard slot. It adds memory, communications, multimedia, and security capabilities to mobile computers.
Cloud storage
Internet service that provides storage to computer users.
optical disc
Type of storage medium that consists of a flat, round, portable disc made of metal, plastic, and lacquer that is written on and read by a laser. Optical disc drive installed in a drive bay; operating system automatically start the program. Store item in a single track that spirals from the center of the disc to the edge of the disc.
Pits
optical disc store item by using microscopic pits (indentations) and lands (flat areas) that are in the middle layer of the disc. High-power laser light creates pits. Lower power laser reads item from the disc by reflecting light through the bottom of the disc. Reflected 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.
mini discs
Optical disc with a size of three inches or less used by smaller computers and devices.
LightScribe technology
used by some optical drives that can etch labels directly on a specially coated optical disc, as opposed to placing an adhesive label on the disc.
jewel box
Protective case that is used to store optical discs when not in use.
CD-ROM
compact disc read-only memory, Type of optical disc that uses laser technology to store data, instructions, and information that users can read but not write on or erase.
single-session disc
Disc on which manufacturers write all items at one time.
CD-ROM drive
Drive that can read CD-ROM discs and sometimes audio CDs.
CD-R
compact disc-recordable, Multisession optical disc on which users can write, but not erase, their own items such as text, graphics, and audio.
multisession
Optical disc that can be written on more than once, allowing users to save additional data on the disc at a later time.
CD-RW
compact disc-rewritable, erasable multisession optical disc on which users can write data, instructions, and information multiple times.
CD-RW drive
Drive that can read audio CDs, standard CD-ROMs, CD-Rs, CD-RWs, and can write on, or record, CD-RWs.
burning
Process of writing on an optical disc.
ripping
Process of copying audio and/or video data from a purchased disc and saving it on digital media.
archive disc
CD that stores photos from an online photo center in jpg file format, usually at a maximum resolution of 7200 pixels per photo.
Picture CD
Single-session CD-ROM that stores digital versions of film using a jpg file format at a lower resolution, typically 1024 x 1536 pixels.
DVD-ROM
digital versatile/video disc read only memory, High-capacity optical disc on which users can read, but not write or erase.
DVD-ROM drive
Device that can read a DVD-ROM. Most DVD-ROM drives also can read audio CDs, CD-ROMs, CD-Rs, and CD-RWs.
Blu-ray Disc ROM
Newer, expensive type of DVD with storage capacities of 100 GB, with expectations of exceeding 200 GB in the future.
HD VMD
versatile multilayer disc, High-density format that potentially will contain up to 20 layers, each with a capacity of 5 GB.
UMD
universal media disc, Mini-DVD used specifically with the PlayStation Portable handheld game console.
BD-R
High-capacity DVD-recordable format.
BD-RE
High-capacity rewritable DVD format.
Tape
Magnetically coated ribbon of plastic capable of storing large amounts of data and information at a low cost.
tape drive
Device used to read and write data and information on tape.
tape cartridge
Small, rectangular, plastic housing for tape.
tape library
Separate cabinet for larger computers in which tape cartridges are mounted.
sequential access
Type of data access in which the storage device reads or writes data consecutively.
direct access
also called random access,
magnetic strip card
Credit card, entertainment card, bank card, or other similar card, with a stripe that contains information identifying you and the card.
smart card
Card, similar in size to a credit card or ATM card, that stores data on a thin microprocessor embedded in the card.
microfilm
A roll of film, usually 100 to 215 feet long, on which microscopic images of documents are stored.
microfiche
A small sheet of film, usually about 4 inches by 6 inches in size, on which microscopic images of documents are stored.
computer output microfilm recorder
Device that records images on microfilm and microfiche.