C plus plus Constants and Variables, Chapter3 - Object Oriented Programming in C plus plus

Computer Science SLO Based Key Point Notes

👉👉👉 Computer Science 12th Class Notes (Main Page)

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Unit 3: Object-Oriented Programming in C++

3.2.1 C++ Constants and Variables

Constant:

• A constant is a quantity that cannot be changed during program execution.
• It can be a number, a character, or a character string. A character string is a sequence of any number of characters.
• Examples: 42, 7.25, ‘s’, “computer” etc.

Variable:

• A quantity whose value may change during the execution of the program is called a variable.
• A variable is a space in a computer’s memory, used to store data and given a name for easy reference. OR
• In C language, a variable is a memory location that is identified by a name to store a data of particular type.

Rules for Naming a Variable:

Following are the rules for naming variables in C:

1. A variable name may consist of digits, upper case, and lower case alphabets, and underscore symbols i.e. “_”
2. The first character of a variable name must be an alphabet character or underscore.
3. Keywords/Reserved words of C++ cannot be used as variable names.
4. Special symbols such as $, @, %, #, etc. are not allowed.
5. Two variables cannot be of the same name.
6. C is a case-sensitive language. Variable names with the same spelling but different cases are treated as different variable names.
7.  A meaningful name should be given to the variable which can help to understand the purpose of the variable.
8. Blank space or comma is not allowed.

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3.1 Introduction to Object-Oriented Programming (OOP):

3.1.1 Computer Program/Software:

3.1.2 Header File and Reserved Words

3.1.3 Structure of C++ Program

3.1.4 C++ program statement Terminator:

3.1.5 Comment statement in C++ Program:

3.2.1 C++ Constants and Variables

3.2.2 Rules for Naming a Variable:

3.2.3 Different C++ data types for variable

3.2.4 The Constant Qualifier (const)

3.2.5 Variable Declaration and Initialization

3.2.6 Type Casting

3.3: Input / Output Handling

3.3.1 The cout Statement

3.3.2 The cin Statement:

3.3.3 The getch() function:

3.3.4 Commonly Used Escape Sequences

3.3.5 Commonly Used Escape Sequences

3.3.6 The Programing with I/O Handling Function

3.3.7 The Manipulators endl and setw

3.4.1 Types of Operator in C++:

3.4.2 UNARY, BINARY AND TERNARY OPERATORS

3.4.3 Order of Precedence of Operator

3.4.4 Expression in C++

4.1.4. The Switch Statement:

Chapter 3 (Complete Key Point Notes)

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👉👉👉 Computer Science 12th Class Notes (Main Page)

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(National Book Foundation - As Federal Textbook Board, Islamabad 

Based on National Curriculum Pakistan 2026-2027 and Onward prescribed by Federal Board of Intermediate and Secondary Education, Islamabad, and All Pakistan Boards) 

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