Concept of Files, Records and Fields

File

• Files are a kind of container or collection of related records that is  used for storing the Data of the users for a Long time Period.
• Files can contain any type of information means they can Store the text, any Images or Pictures or any data in any Format.

For example

 (1) a student file might include all of the records of students enrolled at a school.

(2)A police department might keep a file of criminal records, which includes details about all known criminals.

• ·       Files are stored on secondary storage devices such as hard disks, CD-ROMs etc.

So that there must be Some Mechanism those are used for Storing the information, Accessing the information and also Performing Some Operations on the files

Operation performed on file

Open

• A file can be opened in one of two modes, Read mode or Write mode. In read mode, operating system does not allow anyone to alter data it is solely for reading purpose
• The other mode is write mode, in which, data modification is allowed. Files opened in write mode can be read also but cannot be shared.

Locate

Every file has a file pointer, which tells the current position where the data is to be read or written. This pointer can be adjusted accordingly. Using find (seek) operation it can be moved forward or backward.

Retrieval

Retrieval operation is used to access the data from the file.

Read

By default, when files are opened in read mode the file pointer points to the beginning of file. There are options where the user can tell the operating system to where the file pointer to be located at the time of file opening.

Write

User can select to open files in write mode, which enables them to edit the content of file. It can be deletion, insertion or modification.

Update

Update operations change the data values by insertion, deletion or update.

Close

This also is most important operation from operating system point of view. When a request to close a file is generated, the operating system removes all the locks (if in shared mode) and saves the content of data (if altered) to the secondary storage media and release all the buffers and file handlers associated with the file.

                        Read file organisation and their Techniques CLICK HERE

                        Read Master And Transaction File and More CLICK HERE

Records / Tuples / Rows

• Data is stored in records. A record is composed of fields and contains all the data about one particular person, company, or item in a database.

• A set of records constitutes a file. Record is also known as Tuple or Row.

Collection of related records=Files

In this database, a record contains the data of Students. Records appear as rows in the database table. There are 4 records of 4 different students given below:

Fields/ Column/Attribute

• A table consists of several records(row), each record can be broken into several smaller entities known as Fields.

• A field is part of a record and contains a single piece of data for the subject of the record. It may also be known as Column or Attribute.

Collection of related Fields=Records

• The above Student table consist of four Fields Roll_No, Student_Name, Course, Adhaar_No.

Types of Fields

                 On the basis of length or size fields can be categorized into two category i.e

Fixed Length Field

• Fields that contain a fixed number of bits are known as fixed length fields. A four byte field for example may contain a 31 bit binary integer plus a sign bit (32 bits in all).

• The disadvantage of using fixed length fields is that some part of the field may be wasted when data size is smaller than field size.

• More space is still required for the maximum length case.

Variable Length Field

variable length field is not always the same physical size. Such fields are nearly always used for text fields that can be large, or fields that vary greatly in length. 

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Master And Transaction file and more

File

• Files are a kind of container that is  used for storing the Data of the users for a Long time Period.
• Files can contain any type of information means they can Store the text, any Images or Pictures or any data in any Format.

In this post we are going to discuss following topic:-

1. Transaction File
2. Master File
3. Relationship between Master and Transaction file
4. Difference between Master and Transaction file
5. Reference file
6. Backup file
7. Report file
8. Sort file
9. Archive file

1. Transaction file

• The data stored in these files are temporary by nature, the data in transaction files is used to update the master files.

• This file contains data, only for period of time and after that send to the master file and it is like a journal used in Account Management System.

• Any modification in data is done in transaction file and Transaction files are only used in 
  Batch Processing Systems.

• Once updating has been carried out, the transaction file may be kept in order to permit subsequent 
  recovery of the master file or for auditing purposes but is otherwise redundant

     Example: price of the products, customers order for the products, inserting new data to the database etc.

2. Master file

• The data stored in these files are permanent by nature. It is just like a Ledger used in Account Management.

• The master file contains all the data of the database (account number, address, bank balance, overdraft limit...).

•  It is updated only through recent transactions using Batch Processing System and Master file stores large amount of data.

Example: customer ledgers, student database, employee data of a company.

3. Relationship Between Master and Transaction File

In the above figure, we can see when old master file is merged with recent transaction file and process the both file using batch processing method than new updated master file is generated which contains up- to- date information.

Master file is updated periodically with latest Transaction file.

4. Difference between Master and Transaction file

5. Reference file

• A reference file is mainly used for reference or look-up purposes. Look-up information is that information that is stored in a separate file but is required during processing.

•  For example, in a point of sale terminal, the item code entered either manually or using a barcode reader looks up the item description and price from a reference file stored on a storage device.

6. Backup file

• A backup files is used to hold copies (backups) of data or information from the computers fixed storage (hard disk).

• Since a file held on the hard disk may be corrupted, lost or changed accidentally, it is necessary to keep copies of the recently updated files. In case of the hard disk failure, a backup file can be used to reconstruct the original file.

7. Report file

• Used to store relatively permanent records extracted from the master file or generated after processing.

•  For example you may obtain a stock levels report generated from an inventory system while a copy of the report will be stored in the report file.

8. Sort file

• It stores data which is arranged in a particular order.

• Used mainly where data is to be processed sequentially. In sequential processing, data or records are first sorted and held on a magnetic tape before updating the master file.

 9. Archive file

• An archive file is a file that is composed of one or more computer files along with metadata.

• Archive files are used to collect multiple data files together into a single file for easier portability and storage, or simply to compress files to use less storage space.

To read various file organisation technique Click Here

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File organization, their purpose and various file organization method

 In today post  we are going to discuss following topic:

1. File Meaning
2. File Organization 
3. File Organization Objective
4. File Organisation Technique/ Method 
5. And their pros and cons

File

• Files are a kind of container that is  used for storing the Data of the users for a Long time Period.
• Files can contain any type of information means they can Store the text, any Images or Pictures or any data in any Format.
• So that there must be Some Mechanism those are used for Storing the information, Accessing the information and also Performing Some Operations on the files.

File Organization

• File organization is a way of organizing the data or records in a file.
• It does not refer to how files are organized in folders, but how the contents of a file are added and accessed.
• File organization is very important because it determines the methods of access, efficiency, flexibility and storage devices to use.

File organization objective

Storing the files in certain order is called file organization. The main objective of file organization is

• Optimal selection of records i.e.; records should be accessed as fast as possible.
• Any insert, update or delete transaction on records should be easy, quick and should not harm other records.
• No duplicate records should be induced as a result of insert, update or delete
• Records should be stored efficiently so that cost of storage is minimal.

 File organization technique

There are Various methods of organizing files on a storage media. Some of them are:

• Sequential,
• Random,
• Serial and
• Indexed-sequential
• Heap
• Hash Clustered

1. Sequential file organization

• Records are stored and accessed in a particular order sorted using a key field.
• Retrieval requires searching sequentially through the entire file record by record to the end.
• Because the record in a file are sorted in a particular order, better file searching methods like the binary search technique can be used to reduce the time used for searching a file .
• For example, of the file has records with key fields 20, 30, 40, 50, 60 and the computer is searching for a record with key field 50, it starts at 40 upwards in its search, ignoring the first half of the set.

Pros of sequential file organization

• The sorting makes it easy to access records.
• The binary chop technique can be used to reduce record search time by as much as half the time taken.

Cons of sequential file organization

• The sorting does not remove the need to access other records as the search looks for particular records.
• Sequential records cannot support modern technologies that require fast access to stored records.
• The requirement that all records be of the same size is sometimes difficult to enforce.

2. Random or direct file organization

• Records are stored randomly but accessed directly.
• To access a file stored randomly, a record key is used to determine where a record is stored on the storage media.
• Magnetic and optical disks allow data to be stored and accessed randomly.

Pros of random file access

• Quick retrieval of records.
• The records can be of different sizes.

3. Serial file organization

• Records in a file are stored and accessed one after another.
• The records are not stored in any way on the storage medium this type of organization is mainly used on magnetic tapes.

Pros of serial file organization

• It is simple
• It is cheap

Cons of serial file organization

• It is cumbersome to access because you have to access all proceeding records before retrieving the one being searched.
• Wastage of space on medium in form of inter-record gap.
• It cannot support modern high speed requirements for quick record access.

4. Indexed-sequential file organization method

• Almost similar to sequential method only that, an index is used to enable the computer to locate individual records on the storage media. 
• For example, on a magnetic drum, records are stored sequential on the tracks. However, each record is assigned an index that can be used to access it directly.

5.Heap File Organization

•  When a file is created using Heap File Organization mechanism, the Operating Systems allocates memory area to that file without any further accounting details.
• File records can be placed anywhere in that memory area. It is the responsibility of software to manage the records. Heap File does not support any ordering, sequencing or indexing on its own.

Pros of Heap storage

Heap is a good storage structure in the following situations:

• When data is being bulk-loaded into the relation.
• The relation is only a few pages long. In this case, the time to locate any tuple is Short, even if the entire relation has been searched serially.
• When every tuple in the relation has to be retrieved (in any order) every time the relation is accessed. For example, retrieve the name of all the students.

Cons of Heap storage

Heap files are inappropriate when only selected tuples of a relation are to be accessed.

 6. Hash File Organization

• This mechanism uses a Hash function computation on some field of the records. As we know, that file is a collection of records, which has to be mapped on some block of the disk space allocated to it. 
• This mapping is defined that the hash computation. The output of hash determines the location of disk block where the records may exist.

Pros of Hash file organization

Hash is a good storage structure in the following situations:

• When tuples are retrieve based on an exact match on the hash field value, particularly if the access order is random.
•  For example, if the STUDENT relation is hashed on Name then retrieval of the tuple with Name equal to "Rahat Bhatia" is efficient.

Cons of Hash file organization

Hash is not a good storage structure in the following situations:

• When tuples are retrieved based on a range of values for the hash field. For example, retrieve all students whose name begins with the "R".

7. Clustered File Organization

• Clustered file organization is not considered good for large databases. In this mechanism, related records from one or more relations are kept in a same disk block, that is, the ordering of records is not based on primary key or search key. 
• This organization helps to retrieve data easily based on particular join condition. Other than particular join condition, on which data is stored, all queries become more expensive.

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Intranet,Its Working and Business Value

Hello friends, we are here again with new topic that is Intranet. You will definitely find question regarding Intranet its working, Business Value and Application of Intranet or may be related to Extranet in your BCA/BSC-IT semester exam. So examination point of view this topic is very important.

          Lets begin with Intranet, the road map of today's topic is as follow:-

1. Introduction
2. Working of Intranet
3. Application of Intranet
4. Advantages of Intranet
5. Disadvantages of Intranet
6. Difference Between Internet & Intranet

1.Intranet

Intranet is composed of two words Intra and net where Intra means within the organisation and net means Network. Intranet is a smaller private version of Internet can also say mini-Internet.Moreover we can define Intranet as:

• Intranet is defined as private network of computers within an organization with its own server and firewall. 

• Intranet is system in which multiple PCs are networked to be connected to each other. PCs in intranet are not available to the world outside of the intranet.

• Usually each company or organization has their own Intranet network and members/employees of that company can access the computers in their intranet.

• Each computer in Intranet is also identified by a IP Address, which is unique among the computers in that Intranet.

2.Working of Intranet

Just like user access the information on internet, The employees of the company can access the information from the company's intranet web server using a web browser. This Web server is connected to the company's Local Area Network(LAN).The working of Intranet is as follow:-

• When an employees of a company needs to access company information then he sends a request to web server using web browser.
• The web server retrieves the appropriate web page and send it to the employee's web browser and content is displayed on the employee screen.
• Employee of the company can also access the Internet from the company's Intranet by using a firewall.

3.Application of Intranet/ Business Value

Intranet applications are same as that of Internet applications. Intranet applications are also accessed through a web browser. The only difference is that, Intranet applications reside on local server while Internet applications reside on remote server. Here, we've discussed some of these applications:

Interactive communication Application

Like on internet, we have e-mail and chat like applications for Intranet, hence offering an interactive communication among employees.

Support for Internet Application

Intranet offers an environment to deploy and test applications before placing them on Internet.

Research and development

It is used by the research and development team to provide information related to the project schedule, post technical specification, get feedback from the sales staff etc.

Sales and marketing Application

sales and marketing staff requires up-to date and accurate information about the product and services which is very crucial in today's competitive environment.

Accounting Application

Intranet can help the finance department to post their objective to staff  all around the world. The company's stock prices, current status which can be viewed by various employee and associated customer.

4.Advantages of Intranet

Intranet is very efficient and reliable network system for any organization. It is beneficial in every aspect such as collaboration, cost-effectiveness, security, productivity and much more.

Effective Communication

Intranet offers easy and cheap communication within an organization. Employees can communicate using chat, e-mail or blogs.

Time Saving

Information on Intranet is shared in real time.

Collaboration

Information is distributed among the employees as according to requirement and it can be accessed by the authorized users, resulting in enhanced teamwork.

Platform Independency

Intranet can connect computers and other devices with different architecture.

Cost Effective

Employees can see the data and other documents using browser rather than printing them and distributing duplicate copies among the employees, which certainly decreases the cost.

Workforce Productivity

Data is available at every time and can be accessed using company workstation. This helps the employees work faster.

Business Management

It is also possible to deploy applications that support business operations.

Security

Since information shared on intranet can only be accessed within an organization, therefore there is almost no chance of being theft.

Specific Users

Intranet targets only specific users within an organization therefore, once can exactly know whom he is interacting.

Immediate Updates

Any changes made to information are reflected immediately to all the users.

5.Disadvantages of Intranet

1. Management Concern

• Loss of control 
• Hidden complexity 
• potentional for chaos

2. Security Concern

• unauthorized of services
• denial of services
• packet sniffing

Difference between Internet and Intranet

                           so friends this is all about Intranet.In the next post we will learn about Extranet. Don't forget to leave your comment.

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How Search Engine Works

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Search Engine, Its Working and Types-II

Hi and Welcome back  friends in TechMania. In the last Post we had learn about Search Engine their Architecture, Working and about Web Crawler if you miss that kindly read the Search Engine, Its Working and Types-I  for more clearance of this post . Today we'll continue with last topic that is Search Engine, Its Working and Types-II. In this we are going to learn .......................

• Types of search engine
• Web directory 
• Difference between search engine and web directory
• Market share of various search engine
• Play with Google

Types of search engine

Different blogger catogerize the on various basis but on the their working Search Engine Mainly classify into four category that is mention below:-

1. Crawler based search engine
2.  Meta search engine 
3.  Hybrid search engine
4.  Web directories

1. Crawler based search engine

• Crawler based search engine work with the help of web spider.
• Web spider searches a webpage, download it and analysis the information presented on the webpage and add to the search engine database
• Crawler based search engines are constantly search the internet for new webpage and updating their database
•   Example:- Google , Ask Jeeves, Aliweb, Baidu etc. 

Crawler Based Search Engine

2.Meta Search Engine 

• Take the result from other search engines and web directories like Google, MSN, Lycos etc.
• User can send one request simultaneously to multiple search engine without user intervention
• Meta search receives various result from different search engine and try to extract the most relevant hits
• Example:-Meta crawler, Dogpile, Fazzle, Bighub, kartoo, Infogrid, IceRocket etc.  

3.Web Directories

• Highly structured way of searching information on the WWW.
• Information is organised in hierarchical tree structure .
• Web directory may be organised by alphabetically or topically.
• Also known as indexes or catalogues.
• Web Directories are managed in search engine by directory staff.
• Some directory are paid while other are free.
• Goggle, Yahoo, Looksmart, Zeal, Galaxy, Index,  Apollo, Gimpsy, Excite etc. are the search engine that maintain web directory.

Difference Between Search Engine And Web Directories

4.Hybrid Search Engine

• Hybrid search engine is combination of crawler based search engine and web directory
• Result of the hybrid search engine is shown by the combination of both result
• Example:- yahoo and Bing  

Page Ranking criteria

Different search engine have different ranking criteria of web page. Their ranking criteria can be based on ...........

• Frequency of searched keyword in webpage.
• Number of links(internal or external link).
• Location of keyword either in title or page description.
• Number of clicks on particular webpage.

Market share of various search engine

In the below the market share of various search engine is given below of year 2013 and 2014. After the Google, Baidu search engine have more market share.

Note: Baidu is the China's most used search engine/Browser. In China Google is banned.

Play with Google

To know how play with google play see video!!!!!!!!!!!!!!!!!!!

So friends this is all about search engine how was this topic kindly post your comments so that I'll make more better if you want to know about any specific topic please sent topic name I'll post article on that topic in simple words.I will wait for your comments and reviews.

Good Bye and Have a Nice Day!!!!!!!!!!!!!!

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