1. CSCI 1101 Intro to Computers 4. Computer File Systems

2. 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

3. 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.

4. 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?

5. 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 have.exe file extensions What is an executable file?

6. 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?

7. 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

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

9. File manager utility software  provided by your computer operating system  helps you locate, rename, move, copy and delete files File Management (Windows Explorer)

10. 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

11. 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

12. Operating system’s file manager utility displays lots of information about the files stored on a computer

13. 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?

14.  A file specification (path) is the drive letter, folder, filename, and extension that identifies a file. A:\Word\Gumbo.doc subdirectory (folder) filename extension drive letter Components of a complete file specification

15. 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

16. You can visualize the directory of 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

17. Windows Explorer Windows Explorer's view

18. 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

19. 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

20. 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

21. 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

22. 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

23. Storing data on magnetic media Read-write head Disk surface Mylar disk Magnetic surface storage

24. 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

25. 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

26. Optical storage devices read data using reflected laser light Optical storage illustrated

27. 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?

28. A formatted disk is divided into circular tracks Track / sector illustrations

29. 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?

30. 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

31. Each colored cluster represents part of a file File storage illustration

32. 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?

33. 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?

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

35. 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

36. 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

37. 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?

38. 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?

39. Hard disk platters prevent dust from interfering with read-write heads Hard disk illustration

40. 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?

41. 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?

42. 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

43. 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

44. 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

45. 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?

46. 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?

47. 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