IGCSE Computer Science Paper-1: Specimen Questions with Answers 44 - 45 of 164

Question 44

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State the ACID properties of Database Management System.

Explanation

Image of The Transaction ACID Properties

Image of the Transaction ACID Properties

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The combination of Atomicity, Consistency, Isolation and Durability properties that allows a safe and secure way of data share among multiple users is called the ACID properties.

i) Atomicity: This property means that in case of any update occurring inside the database, the update shall be available to all the users or it will not be available to any user.

ii) Consistency means maintaining the database consistency before or after any transaction that takes place inside the database.

Iii) Isolation: This means that other transactions should not be impacted in case previous transaction is still in progress and yet to be completed.

iv) Durability means the availability of data in the same state even if any failure or restart occurs in the system.

Question 45

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What is the meaning of a web crawler? Also list some of its uses.

Explanation

A web crawler is an automated script which browses the World Wide Web in a methodical, automated manner. The process is better known as Web crawling or spidering. A web crawler is called a web spider or web robot. Some of the popular web crawler examples are Googlebot, Bingbot. Slurp Bot. DuckDuckBot etc.

The figure show web crawler

The Figure Show Web Crawler

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Uses

i) They are mainly used to create copies of all the visited pages for later processing by a search engine.

ii) They are also used for automating maintenance tasks on a Web site for example checking links or validating HTML code.

iii) They can also be sued to gather specific information from Web pages that include harvesting e-mail addresses (usually for spam).

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