Computer Files and Data Storage

Computer Concepts 4th EditionParsons/Oja

CHAPTER

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Data, Information, and FilesSection A

Computer Files and Data Storage


Section D

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4Section A

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Section A

Correctly use the terms “data” and “information” Create valid file names under DOS and Windows Explain how wildcards and file extensions simplify

file access Determine if a file is an executable file or a data

file

Section PREVIEW

You will be able to:

Data, Information, and Files


Data and Information: Technically Speaking

Aren’t data and information the same thing?

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Data is words, numbers, and graphics that describe people, events, things, and ideas.– used by computers

Information is the words, numbers, and graphics used as the basis for human actions and decisions.– used by humans


Computer Files

What kinds of files are stored on a computer?

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File - named collection of data that exists on a storage medium such as a hard disk or floppy drive


File Naming Conventions

May I use any name I want when I create my own files?

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Filename– unique set of letter and numbers– identifies a file– describes the file contents

Filename extension further describes the file contents.– separated by the filename with a dot

You must provide a valid filename that adheres to rules or file naming conventions.


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The asterisk is a wildcard character used to represent a group of characters in the filename or extension.

Wildcards are handy for finding specific files on a hard disk.

Wildcards

Is * * a filename?

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File Extensions and File Types

Why do I need to know about file extensions?

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You can access files efficiently if you are familiar with the characteristics of file categories.


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An executable file contains the program instructions that tell a computer how to perform a specific task.

Most have .exe or .com extensions.

Executable Files

How do I use executable files?

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Executablefiles have .exe fileextensions


Data Files

How do I use data files?

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Section A

A data file contains words, numbers, and pictures that you can view, edit, save, send, and print.– Passive, unlike executable files which are

active– created using application software– receive data files on CD-ROMS such as clip

art You manipulate a data file using the same

software that was used to create it.


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The standard method for opening a data file is to start an application, then use the open command.

A generic filename extension indicates general type of data contained in a file.– a .bmp could be opened in Microsoft Paint

or MicroGrafx Picture Publisher

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Data Files


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An application-specific filename extension is associated with a particular application

Data Files


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Application-specificfilenameextensions


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Other files are necessary for hardware and software operations and should not be deleted.

Configuration Files, and Program Modules

What other kinds of files will I find on my computer?

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F I G U R E 4 - 8

F i l e n a m e E x t e n s i o n s f o r C o n f i g u r a t i o n F i l e s

a n d P r o g r a m M o d u l e s

T yp e o f F i l e D e s c r i p t i o n F i l e n a m e

E x t e n s i o n

B a t c h f i l e A s e q u e n c e o f o p e r a t i n g s y s t e m c o m m a n d s t h a t a r e

e x e c u t e d a u t o m a t i c a l l y w h e n t h e c o m p u t e r b o o t s .

. b a t

C o n f i g u r a t i o n f i l e I n f o r m a t i o n a b o u t p r o g r a m s t h a t t h e c o m p u t e r u s e s

t o a l l o c a t e t h e r e s o u r c e s n e c e s s a r y t o r u n t h e m .

. c f g , . s y s ,

. m i f , . i n i

H e l p T h e i n f o r m a t i o n t h a t i s d i s p l a y e d b y o n l i n e H e l p . . h l p

T e m p o r a r y f i l e A s o r t o f “ s c r a t c h p a d ” t h a t c o n t a i n s d a t a w h i l e a

p r o g r a m i s r u n n i n g , b u t t h a t i s d i s c a r d e d w h e n

y o u e x i t t h e p r o g r a m .

. t m p

P r o g r a m s u p p o r t

m o d u l e s

P r o g r a m i n s t r u c t i o n s t h a t a r e e x e c u t e d i n

c o n j u n c t i o n w i t h t h e m a i n . e x e f i l e f o r a p r o g r a m .

. o c x , . v b x ,

. d l l


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File Manager Utility SoftwareSection B



Section D

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Section B

Describe the difference between logical and physical file storage

Section PREVIEW


File Manager Utility SoftwareSection B


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Section B

File manager utility software – provided by your computer operating

system– helps you locate, rename, move, copy and

delete files

WorksheetsFile Manager Utility SoftwareSection B


Device Letters

Why do storage devices have letters?

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A storage device, such as a floppy disk drive, a hard drive, and a CD-ROM drive, is identified by a letter called a device letter.– floppy disk drive = A– main hard disk = C– additional storage devices = D through Z


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Section B

Directories and Folders

How can I get a list of files that are stored on a disk?

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An operating system maintains a list of files called a directory for each disk, CD-ROM or DVD.

Directory includes– filename– filename extension– date and time file was created– file size


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Section B



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Operatingsystem’s file managerutility displayslots of informationabout the filesstored on acomputer


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Root directory – main directory of a disk– provides a useful list of files

Folders - smaller lists within directories A folder is separated from a drive letter and a

filename by a backslash (\).

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A file specification (path) is the drive letter, folder, filename, and extension that identifies a file.

A:\Word\Gumbo.doc

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drive letter

subdirectory (folder)

filename extension


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Storage Models

How does file manager utility software depict files and folders?

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File manager utility software provides a metaphorical view of the files stored on a computer.– also called logical models

• filing cabinet• tree structure


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Storage Models


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A file cabinet metaphor depicts astorage device as adrawer of a filingcabinet containingfolders and documents.


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Section B

Storage Models


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You can visualizethe directoryof a disk as a tree on its side.

Visualize a disk directory as a tree.– trunk and branches

are folders– leaves are files


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Section B

Storage Models


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WindowsExplorer


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Find - to locate a file Rename - to change the name Copy - to copy a file Move - to move file from one folder to another Delete - when you no longer need a file

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Using File Manager Utility Software

How do I use file manager utility software?

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How Computers Store File DataSection C



Section D

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Section C

Describe the difference between logical and physical file storage

Discuss how the directory and the FAT help you access files

Section PREVIEW




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Section C

The data for a single file can be scattered all over the surface of a disk.

Physical storage - way computer store data on a disk.

Logical storage - conceptual model of files and folders.



Storage Terminology

What are the basic components of a data storage system?

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Section C

Storage medium - the disk, tape, CD, DVD, paper, or other substance that contains data

Storage device - mechanical apparatus that records and retrieves data from a storage medium– floppy disk drives– hard disk drives– CD drives– DVD drives– tape drives


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Storage technology - a storage device and the media it uses.

Storing - also known as – writing data (mainframe applications)– saving a file (Windows terminology)

Retrieving - also known as– reading data (mainframe applications)– loading data– opening a file (Windows terminology)

Storage Terminology

What are the basic components of a data storage system?

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Bits and Bytes

If I enter a letter or number how is it actually stored?

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Section C

Computers use codes to convert information into digital data.– series of 1s and 0s

Bit - smallest unit for digitizing data Byte - 8 bits A byte represents:

– a character– a space– numeral– punctuation


Magnetic and Optical Technologies

How does a computer get the 1s and 0s onto the storage medium?

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1s and 0s are changed in the surface of the storage medium.

Transformation depends on storage technology. Magnetic storage - stores data by magnetizing

microscopic particles on the disk or tape surface Read-write head - mechanism in the disk drive

that reads and writes magnetized particles that represent data


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Storing dataon magneticmedia

Read-write head

Disk surface

Mylar disk


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Data stored on magnetic media such as floppy disks can be altered by dust, smoke, heat, and mechanical problems.

Some experts estimate that the reliable life span of data stored on magnetic media is about three years.


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Optical storage stores data as microscopic light spots (lands) and dark spots (pits) on the disk surface.

Data stored on an optical storage device is less susceptible to environmental damage.



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Optical storage devicesread data using reflectedlaser light


Tracks, Sectors, and Clusters

Is data stored in specific places on a disk, tape, or CD?

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Tracks - electronic storage bins– parallel to the edge of the tape– spiral out from the center of the disk– arranged as concentric circles or

Tracks that are arranged in concentric circles are divided into wedge-shaped sectors

Cluster - a group of sectors


Tracks, Sectors, and Clusters

Is data stored in specific places on a disk, tape, or CD?

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A formatteddisk is divided intocircular tracks


File Allocation Tables

How does a computer keep track of the location of every file?

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File allocation table (FAT) - an operating system file that maintains a list of files and their physical location on the disk.– like a table of contents– a damaged FAT results in losing data

Back up data on hard disk.


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Computer looks for empty clusters to store data

Name of new file and number of cluster are recorded in the FAT

Files that do not fit in one cluster spill over to contiguous or noncontiguous clusters, depending on availability.

Pointers - instructions that point to each piece of the file



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Each coloredclusterrepresentspart of a file


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It takes longer to retrieve a file stored in noncontiguous clusters.

When you delete a file, the clusters’ status becomes “empty” but retains old data until new data is stored.

You may be able to retrieve data using an undelete utility.– Recycle Bin’s Restore feature



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Files stored in many noncontiguous clusters become fragmented.– drive performance declines– becomes harder to locate clusters

A defragmentation utility rearranges files in contiguous clusters– improves drive performance



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Disks, Tapes, CDs, and DVDsSection D



Section D

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Section D

Select a storage device based on characteristics such as its capacity and access speed

Section PREVIEW




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Section D

There are many types of storage devices, each with unique advantages and disadvantages.



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Versatility

– can access data from different media Durability

– less susceptible to damage Storage capacity - maximum amount of data that

can be stored on a storage medium

– kilobyte = approximately 1000 bytes

– megabyte = approximately 1 million bytes

– gigabyte = approximately 1 billion bytes

– terabyte = approximately 1 trillion bytes

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Speed - measured by access time and data transfer rate

Access time - average time it takes a computer to locate data and read it– millisecond = one-thousandth of a second

Random access - ability of a device to jump directly to the track or sector holding the data– floppy disk, hard drive, CD, DVD

Chapter

4Disks, Tapes, CDs, and DVDsSection D

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Sequential access - reads through from beginning of tape– tape drive

Data transfer rate - amount of data that moves per second

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Floppy Disk Storage

Why is it called a floppy disk?

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Floppy disk - round piece of flexible mylar plastic covered with thin layer of magnetic oxide.– sealed in protective casing– also called floppies or diskettes– inside casing is “floppy”– not as speedy as zips– decreased use

Zip disk - high-capacity floppy disk manufactured by Iomega Corporation.


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Floppy Disk Storage


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Double-sided disk - stores twice as much as single-sided

Disk density - closeness and size of magnetic particles it stores

High-density disk - stores more data than double-density


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Floppy Disk Storage


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Disk capacities


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Hard disk platter - a flat, rigid disk made of aluminum or glass and coated with magnetic oxide– density far exceeds floppy disk

Hard disk - one or more platters and their associated read-write heads.– preferred type of main storage

Cylinder – vertical set of tracks– basic storage bin for hard disk drive

Hard Disk Storage

How can a hard disk be the same size as a floppy, but store so much more data?

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Hard Disk Storage


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Hard diskplatters preventdust from interfering withread-writeheads


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Hard disks– provide random access to files– faster than floppy disk access– continually in motion

Hard Disk Storage


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Head crash - when a read-write head runs into a dust particle or other contaminant on the disk.– head crash damages some data on disk– triggered by jarring the hard disk while in

use Removable hard disk - hard disks that can

be inserted and removed from drive– increase storage capacity– provides security for data

Hard Disk Storage


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RAID - (redundant array of independent disks)– type of hard disk storage– found on mainframe and microcomputer

installations– contains many disk platters– provides redundancy– faster data access

Hard Disk Storage


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Disk cache – special area of computer memory– computer transfers data you are likely to

need– reads data from nearby sectors and stores

it in the cache

Hard Disk Storage


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Tape– most popular form of storage in 1960s– continued in form of cassette tape drive– requires sequential access– inconvenient and slow

Recent revival in tape storage for backing up data, not for principal storage device.

Tape backup - copy of data on hard disk stored on magnetic tape.

Tape Storage

Do they still use those big tape drives on computers that you see in old movies?

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Open reel tapes– large reels seen in old movies– access speeds measured in seconds– still used as distribution medium for some

mainframe and minicomputer systems Tape cartridge - a removable magnetic tape

module similar to a cassette tape.

Tape Storage

Do they still use those big tape drives on computers that you see in old movies?

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CD-ROM– stands for Compact Disc Read-Only Memory– data stamped on when manufactured– holds up to 680 MB– coated with clear plastic, durable– estimated life exceeds 500 years– inexpensive to manufacture– ideal for distribution of large files

CD-ROM Technology

If CD-ROMS are read only, doesn’t that limit their use?

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CD-ROMS– choice for delivery of multimedia

applications– read-only storage memory

Read-only - computer can retrieve from it but not save new data on it

CD-ROM drives– standard on today’s computers– speeds up to 40X

CD-ROM Technology

If CD-ROMS are read only, doesn’t that limit their use?

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CD-R– stands for compact disc-recordable– allows you to create your own CDs by

recording on a CD-R disk Recording is done on a CD-R drive

– uses a laser to change the reflectivity of a dye layer on a blank CD-R disk.

CD-R Technology

Can I make my own CD-ROMs?

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Disks produced on CD-R drive – can be used on CD-ROM and DVD drives– cannot be erased or modified– some drives have multisession support

(can record in multiple sessions)• available after 1998

Archiving - moving data that is not accessed frequently off of a primary storage device

CD-R Technology

Can I make my own CD-ROMs?

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CD-RW (compact disc-rewritable) allows you to write on a CD, then change the data– requires special CD-RW disks– requires special CD-RW drive– requires phase change technology

Phase change technology - alters the crystal structure on the disk surface

CD-RW Technology

Is there any way to change the data on a CD?

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DVD (digital video disc or digital versatile disc)

– variation of CD technology

– designed to provide enough storage capacity for a full length movie

– will replace video tape (experts believe) DVD-ROM disk

– stamped with data when manufactured

– cannot change or add data

– stores 4.7 GB

– ideal for games, maps, large databases

DVD Technology

How is DVD different from CD technology?

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DVD+RW– uses phase change technology– cannot be used on DVD-RAM

DVD-RAM– uses a blend of technologies to record data– cannot be used on DVD+RW

Both DVD+RW and DVD-RAM can be read on DVD-ROM drives.

DVD+RW and DVD-RAM Technology

Is there a DVD equivalent to CD-RW?

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Computer Files and Data Storage

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