long

• File


  A collection of related records used as a single unit, also known as a data set
• File


  • Stored on different storage media such as hard disk, USB flash drive or optical disc
  • May contain records of hundreds of employees
  • Each employee's record consists of same fields but each field contains different data
• Employee file fields


  • Name
  • EmployeeID
  • HireDate
  • JobTitle
  • Phone
• Master File

  the latest updated files

  are never empty

  Used to store information that remains constant for a long period of time

  updated when changes are required,
• Transaction File


  Stores input data before processing, may be temporary and exist until master file is updated, may also be used to maintain a permanent record of data about a transaction
• Backup File


  Used to take backup of important data, is a permanent file, stores an additional copy of data that can be recovered if original file is lost or damaged, mostly created using specific software
• Program File


  Contains software instructions,

  program file has .com or .exe extension,

  contains instructions that can be directly executed by the computer
• Data File


  Contains data, created by the software being used,

  different software store data in data file using different formats, can be opened in the same or different software that supports the format
• Examples of data files and software

  • Text File (.txt) in Notepad
  • Document (.doc, .rtf) in Word Processor
  • Worksheet (.xls, .wks) in Spreadsheet
  • Data File (.dat, .dbf, .mdb) in Database
  • Image File (.tif, .jpg, .eps, .gif, .bmp) in Image Processor
  • Audio File (.wav, .mid) in Audio Software
  • Video File (.avi, .mpg) in Video Software
• Sequential File Organization


  Records are stored in sequence,

  records are stored one after the other, they can only be retrieved in the sequence they were stored

  disadvantage is slow processing time
• Direct or Random File Organization


  Records are not stored in a particular sequence,

  key value of a record is used to determine the location to store the record,

  each record is accessed directly without going through preceding records,

  it is faster than sequential file organization

  it may have the problem of synonyms if the same address is calculated to store two or more records
• Indexed Sequential File Organization


  Records are stored in ascending or descending order based on a key value,

  maintains an index file with key values and corresponding disk addresses,

  allows both sequential and random access,

  requires more storage space but is as fast as the random or direct file organization
• File Processing System


  A set of programs used to manage data stored in files, programs are developed independently and each defines and manages its own data files, records in one file may not be related to records in other files
• Problems/Disadvantages in Traditional File Processing Approach

  • Data Redundancy
  • Data Inconsistency
  • Program Data Dependency
  • Lack of Flexibility
  • Integrity Problems
  • Security Problems
• Database


  A collection of logically related data sets or files, each file may contain different types of information and are used for specific purposes, files may be organized in different ways to meet different processing and retrieval requirements
• Database systems provide facilities not available in traditional file processing systems
• File Processing System


  A set of programs used to manage data stored in the files
• File Processing System


  • The programs are developed independently
  • Each program defines and manages its own data files
  • The records in one file may not be related to the records stored in other files
• Departments in a typical file processing system

  • Personal dept.
  • Sales dept.
  • Accounting dept.
• Data Redundancy


  Duplication of data in multiple files
• Data Inconsistency


  Different data of the same entity in different files
• Program Data Dependency


  Relationship between data in files and program required to update and maintain the files
• Program Data Dependency


  • If the format of file is changed, the application program also needs to be changed accordingly
• Lack of Flexibility


  It can take a lot of time to collect the data from different files and write programs to produce the desired information
• Integrity Problems


  Difficulty in applying consistency constraints on files

  it means reliability and accuracy of data
• Security Problems


  Inadequate security on data, different access levels for different users are not available
• Database


  A collection of logically related datasets or files.

  each file may contain different type of information and are used for specific purpose.