ICSE IMPORTANT 2 MARK QUESTIONS COMPUTER, Summaries of Computer science

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Java revisions

What are the character sets available in java?

Java uses character sets while writing a program. The

character sets are

• Letters
• Digits
• Operators
• Delimiters

What is an Unicode?

• It is a 16 bit code
• It uses hexadecimal to express a character
• capable to represent almost every character of well-known

languages of the world.

• Standard encoding system used to encode a character in any

computer language

What are escape sequence?

• Java have certain nongraphic characters (nongraphic characters are

those characters that can not be

• typed directly from keyboard e.g. backspace, tab, carriage return etc.).
• Those nongraphic character can be represented by escape sequence. An

escape sequence is represented by backslash followed by one or more

character.

• The few escape sequence characters are:
• \n - new line
• \t - Horizontal Tab
• \v - Vertical Tab
• \b – Backspace
• " - Double Quotes etc.

What are literals? How many types of integer literals

are available in Java?

• A literal is sequence of characters used in a program to represent a constant

value.

• It is otherwise called as constants.
• For example 'A' is a literal that represents the value A of type char, and 17L is

a literal that represents the number 17 as value of type long.

Different types of literals available in Java, they are:

• Integer literal
• Float literal
• Boolean literal
• Character literal
• String literal
• null literal

What is an identifier? What is the identifier

formatting rule of Java? OR What are the rules for

naming a variable?

• Identifiers are names given to different parts of a program

e.g. variables, functions, classes etc.

• The identifiers in Java
  • Can contains alphabets, digits, dollar sign and underscore.
  • Must not start with a digit.
  • Can not be a Java keywords.
  • Can have any length and are case-sensitive.

State the difference between = and ==.

• = is an assignment operator, which assigns value to a variable.
• == is a relational operator, which is used for checking equality or not of two items.

State the difference between token and

identifier.

• The smallest individual unit in a program ,such as keyword, identifier, literal, etc. is called a Token.
• Whereas, Identifier is a name given to a variable or class or object or array or a method.

5. State the two types of Java programs

Ans: - 1. Stand Alone Application

2. Internet Applet

6. State the the difference between boolean

literal and character literal

Ans: - A boolean literal can be either 'true' or 'false' as its value. A character literal is composed of a single character enclosed within a pair of single quotes, e.g., 'A'.

8. Name OOP's principles.

• Ans: - Abstraction, Encapsulation, Inheritance, Polymorphism.

9. Define bytecode.

• Ans: - Bytecde is a platform independent Java instruction for the Java processor chip called JVM.

11. Define Encapsulation.

• Ans: - Wrapping of data and functions of a class together so that they can be applied as a unit to perform any operation is termed as Encapsulation.

12. Define Abstraction.

• Ans: - Abstraction refers to an act of representing essential features without including background details.