Lesson Notes By Weeks and Term - Senior Secondary School 2

Class: SSS 2

Term: 2^nd Term

Subject: Computer Science

Week 4

Topic: Methods of Accessing Files

FILE ORGANIZATION

File organization is a way of organizing the data or record in a file. It does not refer to how files are organised in folders but how the contents of a file are added not accessed. There are several types of file organisation methods. The most common of them are sequential, relative and indexed. They differ in how easily records can be accessed and the complexity in which records can be organized. In modern computer system, files are typically accessed using names also known as file name. Most computers organize files into hierarchies using folders, directories or catalogs. The concept is the same irrespective of the terminology used. Each folder can contain an arbitrary number of files, and it can also contain other folders. These other folders are referred to as sub folders. Sub folders can contain still more files and folders and so on, thus building a tree – like structure in which one “master folder” can contain any number of levels of other folders and files.

There are 4 methods of organizing files These are:

1. sequential
2. line – sequential
3. indexed – sequential
4. inverted list
5. direct and hashed access

TYPES OF FILE ORGANISATION

1. SERIAL: Records in a series are inserted as they The file is usually read serially from beginning to end. Searching individual records is difficult because in each case the entire file must be read. Serial files are usually used for temporary storage of transaction data.
2. SEQUENTIAL FILES: Records are arranged in key value order, usually ascending but it can also be in descending The file is usually read in the order in which it is written, from beginning to the end. The great strength of sequential files is that two sequential files which share a key field and are ordered in the same way can be merged very efficiently.
3. INDEXED SEQUENTIAL FILES: Many applications require a mixture of low and high hit rate. In these cases, neither sequential nor direct organisation is Indexed sequential files are idea for such applications. Because the records are organised sequentially, high hit rate processing is well supported. Direct access of individual records for low hit rate application is provided by an index.
4. RANDOM OR DIRECT FILES: With direct or hashed access, a portion of disk space is reserved and a “hashing” algorithm computes the record address. So there is additional space required for this kind of file in the store. Records are placed randomly throughout the file and are accessed by addresses that specify their disc

A sequential file contains records organised in the order they are entered. The order of the record is fixed.

Disk Boss provides a number of file classification plugins allowing one to classify files by the category, extension, user name, file size, last access, modification and creation time, etc. Disk Boss is an automated, rule- based data management solution allowing one to perform disk space utilization analysis, file classification, duplicate files search and cleanup, high-speed file synchronization and data migration, bulk file delete and secure data wiping, disk change monitoring, automated, policy-based file management and much more. Disk Boss allows you to generate various types of charts and export file classification result into a number of standard such as HTML, XML, text and excel CSV.

Disk Boss is capable of scanning disk network shares and storage devices and it automatically recognizes more than 3,500 types of files, it is capable of classifying files and showing a categorized hierarchy of files sorted by the amount of the disk space used by each file category. Disk Boss includes a number of file classification plugins capable of classifying files by the file type, extension, user name, last access, modification and creation dates, etc. In order to classify files in one or more disks or directories, select the required directories in the Disk Boss file navigator and press the ‘Classify’ button. It also performs various file management operations on specific files or file categories and physically reorganizes files according to user defined rules and policies.

ASSESSMENT

1. Access in which records are accessed from and inserted into file, is classified as
   • direct access
   • sequential access
   • random access
   • duplicate access
2. In computer programming, particular way by which data records are arranged into a specific manner is considered as
   • organization
   • reorganized
   • managing
   • record storage
3. Ability to obtain data from a storage device by going directly to where it is physically located on device rather than by having to sequentially look for data at one physical location after another is called
   • sequential access

• timed access
• direct access
• variable access

4. Method by which program read from files and writes data into file is considered as
   • access
   • organization
   • recording
   • selection
5. Smallest piece of data that could be deal separately is classified as
   • file record
   • item
   • data column
   • bug

ANSWERS

1. b
2. a
3. c
4. a
5. b