Class IX - Computer Application - Chapter 4: Values and Data Types

1. Chapter 4: Values and Data Types

Content 

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1. Character Sets
2. ASCII Character Sets
3. Unicode Character Sets
4. Escape Sequence
5. Tokens
6. Data Types
7. Variables
8. Constants(Named and Symbolic Constants)

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 Point at a Glance

• A character Sett is defined list of character that can be used by a computer.
• The ASCII character set is a 7-bit set of code that allows 128 different character set (2⁷ =128)
• The Extended ASCII code is a 8-bit character set that allows 256 different character(2⁸ =256).
• The Unicode character set uses between 8 and 32 bits per character so it can represent characters from written languages throughout the world.
• An escape sequence is a set of characters that has a special meaning to the Java compiler. In an escape sequence, a character is preceded by a backslash ()
• Java offers five tokens - keywords, identifiers, literals, punctuators, and operators
• Keywords have a special meaning to the Java compiler.
• Identifiers are used in a Java program to name things such as variables, methods, classes, objects etc.
• Literal is a sequence of characters that represent values in a program and are stored in variables.
• Punctuators are symbols used for grouping and separating the code.
• Operators are symbols used to perform arithmetic or logical operations in a given expression.
• Java offers two categories of data types - primitive and non-primitive.
• There are eight primitive types in Java which are: byte, short, int, long, char, float, double and boolean.
• A variable is an identifier that denotes a storage location in computer's memory to store a data value.
• Memory locations whose values cannot be changed within a program are called constants or symbolic constants.
• In Java, the modifier final can be applied to a variable declaration to ensure that the value stored in the variable cannot be changed after the variable has been initialized.