Top Banner
CSCI 1101 Intro to Computers 4. Computer File Systems
47

CSCI 1101 Intro to Computers

Feb 25, 2016

Download

Documents

Gin Gultia

CSCI 1101 Intro to Computers. 4. Computer File Systems. Remember - data/information distinctions. Data is words, numbers, and graphics that describe people, events, things, and ideas. used by computers - PowerPoint PPT Presentation
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: CSCI 1101 Intro to Computers

CSCI 1101 Intro to Computers

4. Computer File Systems

Page 2: CSCI 1101 Intro to Computers

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

Remember - data/information distinctions

Page 3: CSCI 1101 Intro to Computers

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

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.

Page 4: CSCI 1101 Intro to Computers

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.

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

What is a wildcard all about?

Page 5: CSCI 1101 Intro to Computers

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

Most have .exe or .com extensions.Executablefiles have .exe fileextensions

What is an executable file?

Page 6: CSCI 1101 Intro to Computers

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.

What is contained in a data file?

Page 7: CSCI 1101 Intro to Computers

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 An application-specific filename extension is

associated with a particular application

How do you access a data file

Page 8: CSCI 1101 Intro to Computers

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

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 xe 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

Operating system files

Page 9: CSCI 1101 Intro to Computers

File manager utility software provided by your computer operating system helps you locate, rename, move, copy and delete

files

File Management(Windows Explorer)

Page 10: CSCI 1101 Intro to Computers

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

Drive designations

Page 11: CSCI 1101 Intro to Computers

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

File extensions are frequently hidden in these displays, which can cause problems.

File directories

Page 12: CSCI 1101 Intro to Computers

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

Page 13: CSCI 1101 Intro to Computers

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 (\).

What is the Root Directory?

Page 14: CSCI 1101 Intro to Computers

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

A:\Word\Gumbo.doc

subdirectory (folder)

filenameextension

drive letter

Components of a complete file specification

Page 15: CSCI 1101 Intro to Computers

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

filing cabinet tree structure

Logical models for file management

Page 16: CSCI 1101 Intro to Computers

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

Visualizing a disk storage structure

Page 17: CSCI 1101 Intro to Computers

WindowsExplorer

Windows Explorer's view

Page 18: CSCI 1101 Intro to Computers

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

Common file management activities

Page 19: CSCI 1101 Intro to Computers

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

Common Storage terminology

Page 20: CSCI 1101 Intro to Computers

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 activities

Page 21: CSCI 1101 Intro to Computers

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

How is data (logically) stored

Page 22: CSCI 1101 Intro to Computers

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

How is data physically stored

Page 23: CSCI 1101 Intro to Computers

Storing dataon magneticmedia

Read-write head

Disk surface

Mylar disk

Magnetic surface storage

Page 24: CSCI 1101 Intro to Computers

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.

Limitations of magnetic storage

Page 25: CSCI 1101 Intro to Computers

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.

Optical Storage technologies

Page 26: CSCI 1101 Intro to Computers

Optical storage devicesread data using reflectedlaser light

Optical storage illustrated

Page 27: CSCI 1101 Intro to Computers

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

How are disks organized?

Page 28: CSCI 1101 Intro to Computers

A formatteddisk is divided intocircular tracks

Track / sector illustrations

Page 29: CSCI 1101 Intro to Computers

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.

Why is a FAT important?

Page 30: CSCI 1101 Intro to Computers

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

How files get stored

Page 31: CSCI 1101 Intro to Computers

Each coloredclusterrepresentspart of a file

File storage illustration

Page 32: CSCI 1101 Intro to Computers

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

How does "undeleting" a file work?

Page 33: CSCI 1101 Intro to Computers

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

What is fragmentation all about?

Page 34: CSCI 1101 Intro to Computers

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

Page 35: CSCI 1101 Intro to Computers

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

Data storage issues to consider

Page 36: CSCI 1101 Intro to Computers

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

More issues to consider

Page 37: CSCI 1101 Intro to Computers

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.

What is a floppy disk?

Page 38: CSCI 1101 Intro to Computers

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

How is a hard disk different?

Page 39: CSCI 1101 Intro to Computers

Hard diskplatters preventdust from interfering withread-writeheads

Hard disk illustration

Page 40: CSCI 1101 Intro to Computers

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

What is a disk crash?

Page 41: CSCI 1101 Intro to Computers

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

How do servers improve drive reliability?

Page 42: CSCI 1101 Intro to Computers

CD-ROM stands for Compact Disc Read-Only Memory holds up to 680 MB estimated life exceeds 500 years inexpensive to manufacture ideal for distribution of large files 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 essentials

Page 43: CSCI 1101 Intro to Computers

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 variants

Page 44: CSCI 1101 Intro to Computers

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

Uses for CD-R drives

Page 45: CSCI 1101 Intro to Computers

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

What about reusable CDs?

Page 46: CSCI 1101 Intro to Computers

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

How is DVD different from CD technology?

Page 47: CSCI 1101 Intro to Computers

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.

Reusable DVD issues