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Topic 1 — C++ Foundations (Zero → Exam Level)

These basics often appear in MCQ + short answers.

1. Keywords

Reserved words in C++ with fixed meaning.

Examples:

• int
• float
• if
• else
• while
• for
• return

Exam Definition:

Keywords are reserved words in C++ that have predefined meaning and cannot be used as variable names.

2. Identifiers

Names given to variables, functions, arrays, classes.

Example:

Here:

• age = identifier
• salary = identifier

Rules:

• Start with letter or _
• No spaces
• No special chars
• Cannot be keyword

Valid: sum _data marks1

Invalid: 1sum for my-data

Exam Definition:

Identifiers are user-defined names used to identify variables, functions, arrays, etc.

3. Constants

Fixed values that do not change.

Examples:

Types:

• Integer constant
• Float constant
• Character constant
• String constant

Exam Definition:

A constant is a value that remains unchanged during program execution.

4. Variables

Memory location storing data.

a = variable.

Definition:

A variable is a named memory location used to store data.

5. Data Types

Tell compiler what kind of data.

Main types:

6. Operators

Used to perform operations.

Arithmetic

+ - * / %

Relational

== != > < >= <=

Logical

&& || !

Assignment

=

7. Input / Output

• cin → input
• cout → output

8. #include <stdio.h> / basics

PYQ repeated.

It is a preprocessor directive. Used to include standard input-output header file.

Exam line:

#include <stdio.h> is a preprocessor directive used to include standard I/O functions.

9. Small difference (very common)

Keyword vs Identifier

10. Easy MCQs (PYQ style)

Answer fast:

1. for is? → Keyword

2. abc1 is? → Valid identifier

3. 3name valid? → No

4. Fixed value? → Constant

5. #include<stdio.h> ? → Preprocessor directive

Ultra-short revision

Remember: KIC VDO

• K = Keyword
• I = Identifier
• C = Constant
• V = Variable
• D = Data Type
• O = Operator

Mini test (answer without overthinking):

1. Is while keyword or identifier?
2. Is _sum1 valid identifier?
3. 3.14 is what type constant?
4. Which operator = logical AND?
5. char stores what?