BSc. Solutions and Notes: 2073-Solution of Computational Course (Computer Science) : Long Answer Question

Long Answer Question

Attempt any TWO questions.

1) What is Database Management System (DBMS)? What are the benefits of using this system? Discuss different area of DBMS. (2+3+5)

Ans:

A database is an organized collection of logically related data that contains information relevant to an enterprise. A database management system (DBMS) is the set of programs that is used to store, retrieve and manipulate the data in convenient and efficient way. The main goal of DBMS is to hide complexities of data management from users and provide easy interface to them. Examples of DBMS structure are Oracle, Sybase, Microsoft SQL Server, Dbase, etc.

(Note: avoid writing long answer for short question. Normally 10 marks question needs 2 page( i.e. front and back page). So for 3 marks, you can estimate how much do you need to write.)

Some of the advantages of DBMS are:

Data Redundancy - Flat file systems suffered from the problems of high data redundancy which leads to higher storage and access cost.
Data Inconsistency - Data inconsistency is side effect of data redundancy. Data inconsistency occurs if changed data is reflected in data files in one place but not elsewhere in the system.
Data Isolation - Database management systems provide shared access to centrally stored data therefore it is easy for application programs to retrieve required data from centralized database.
Difficulty in Accessing Data - File processing systems do not allow required data to be retrieved in efficient and convenient way.
Integrity Problems - Database management systems allow us to specify integrity constrains on data. Therefore it is easy to maintain correctness of data.
Atomicity Problems - Execution of transaction must be atomic. This means transactions must execute at its entirely or not at all.
Concurrent Access Anomalies - Concurrent updates to same data by different transactions at the same time may result in inconsistent data. Database systems supports concurrent execution of transaction on the same data without resulting into inconsistent data.
Security Problems - In a database system we may create different user accounts and provide different authorization to different users. Thus we are able to hide certain information from some users.

Some of the most common DBMS applications are:

Airlines and Railways - They use online database for reservation and for displaying and schedule information.
Banking - Banks use database for customer inquiry, accounts, loans and other transactions.
Education - Schools and colleges use database for course registration, result and other information.
Telecommunications - Department of IT use database to restore or store information about the telecommunication network, telephone numbers, records of calls for generating monthly bill, etc.
Credit Card Transaction - Database are used for keeping tracks of purchase on credit cards in order to get or generate monthly statements.
E-commerce - Integration of heterogenous information sources for the business activity such as online shopping, booking of holiday packages, etc.
Healthcare Information Systems and Electronic Patient Record - Database are used for maintaining the patient health care details.
Digital Libraries and Digital Publishing - Database are used for management and delivery of large bodies of textual and multimedia data.
Finance - Database are used to store product, customer and transaction details.
Human Resource - Organizations use database for storing information about their employees, salaries, benefits, taxes and for generating salary cheques.

2) Define cryptography. Discuss secret key cryptography. How is it different from public key cryptography? (2+4+4)

Ans:

It is the art and science of making crypto system that is capable of providing information security. Cryptography deals with the actual securing of digital data. It refers to the design of mechanisms based on mathematical algorithms that provide fundamental information security services.

The word cryptography means “secret writing” and is the art and science of information hiding. In ancient days, it was mostly referred as encryption (readable plain text to unreadable) and decryption.

In the public key encryption, the private key can only be used to decrypt the data that was encrypted using the matching public key. Similarly data encrypted using private key can only be decrypted using the matching public key. However, the private key cannot be used in the place of the public key.lIf the locking key is made private, this system makes it possible to verify that the documents were locked by the owner. The reason is that a message encrypted by the sender can only be opened by the person with the matching public key, thus verifying that sender did actually hold the private key (meaning the original non tampered message has been received). Therefore, this is used for digital signatures.

The differences between secret key and public key are:

Secret/Symmetric Key	Public Key
Same key is used for encryption and decryption. Key must be kept secret.	Different keys are used. Key used for encryption is called public key and for decryption is called private key.
Encryption and decryption process is more faster than public key.	Slower.
It cannot be used for other systems than achieving confidentiality.	Can also be used in digital signatures and authentication systems.
Secrecy of the system entirely depends upon shared secret key. So if the key is lost, then whole system will fail.	Relatively more secure than private key.
Useful in the system where it is possible to share the secret key by meetings.	Useful when communication parties are at distant location and is difficult to share secret key.
It is feasible when numbers of users that is involved in communication is few.	Also feasible when the number of users that involve in communication is large.
Examples : caesar cipher, transportation cipher, etc.	Examples : RSA algorithm, EIGamal, etc.

3) What is Internet? Discuss any four Internet services in detail. (2+8)

Ans:

Internet is a global network providing variety of information and communication facilities, consisting of interconnected networks using standardized communication protocols. The word internet comes from combination between “interconnection” and “network”. Network is a collection of computers and devices connected via communication channels and transmission media allow to share resources (hardware, software, data, information). Generally nobody owns internet. Vinton Cerf is the Father of Internet.

Following are the services of internet:

Electronic Mail : Electronic mail (E-mail) is used to send electronic message over the internet. It provides services that allowed complex communication interaction. It provides following facilities:
- composing and sending/receiving a message.
- Storing, forwarding, deleting, replying to a message.
-Sending a single message to more than one person.
-Sending text, voice, graphics and videos.
Telnet : It is used to log on to a remote computer that is attached to internet. TELNET stands for Terminal Network. It is both TCP/IP application. It provides direct access to various services on Internet. Some of these services are available on your host, but Telnet is especially useful when these services are not available on your host.
World Wide Web (WWW) : Commonly known as web, most popular internet service. It is a system of interlinked hypertext documents(called web pages) contained on the internet. A webpage contain text, graphics, animations, sounds and videos. All of the web pages maintained by an organization or individual are called a web site. WWW uses Hypertext Transfer Protocol (HTTP) for fetching files in the internet. A web browser is a software application used to locate and display web pages. Some popular browser are, Microsoft Internet Explorer, Mozilla Firefox, Google Chrome, etc. Web server is a computer that delivers webpages. Every webpage in the internet has an address called Uniform Resource Locator (URL). URL is an addressing scheme used by web browsers to locate document and other resources on the WWW.
File Transfer : File transfer is the process of copying or moving a file from one computer to another over a network or Internet connection. It enables sharing, transferring or transmitting a file or a logical data object between different users and/or computers both locally and remotely.
A file transfer can be an upload or download. File Transfer Protocol (FTP), Hypertext Transfer Protocol (HTTP), BitTorrent and Simple File Transfer Protocol are the most common file transfer protocols used in computer networks and online.
There are two main types of file transfer:
a) Pull-Based: The file transfer request is initiated by the receiver.
b) Push Based: The file transfer request is initiated by the sender.
Moreover, other than network or Internet, file transfer can be performed manually by copying a file to a new folder/drive in the same computer or by copying it on a USB pen drive, CD or other portable storage device to be transferred to another computer.