VARIABLES IN C++…
VARIABLES IN C++
Variable என்பது program execution போது data/value-ஐ store செய்ய பயன்படுத்தப்படும் named memory location. Simple definition: A variable is a named memory location used to store a value that can change during program execution.
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69 programs 11 MCQs v2
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Definition
Variable என்பது program execution போது data/value-ஐ store செய்ய பயன்படுத்தப்படும் named m……
Explanation
Example
int age = 25; இதில்: int → Data type age → Variable n……
Real Life Example
ஒரு box-க்கு Marks என்று name வைக்கிறோம். அதற்குள்: 90 store செய்கிறோம். Later: 95 என்று change……
Explanation
Why variable is needed
Program-ல் values temporary-ஆக store செய்ய வ……
Output
Result
இதற்காக variables use செய்கிற……
Explanation
Example
int age = 20; float salary = ……
Flow
Variable declaration ↓ Memory allocated ↓……
Explanation
Example
int x = 10; Conceptually: Variable Name : x Data Type : int Value : 10 Memory : allocated……
Explanation
Declaration
Variable-ன் name மற்றும் data type compiler-க்கு introduce ……
Explanation
Initialization
Variable create செய்யும் நேரத்திலேயே initial value க……
Explanation
Assignment
Already existing variable-க்க……
Explanation
இதில்: int marks; Declaration.…
Practice
Assignment.
DECLARATION vs INITIALIZATION vs ASSIGNMENT இந்த difference மிகவும் imp……
Practice
Assignment
x = 20; Existing variable-க்க……
Explanation
return 0; }…
Explanation
int marks = 80; Breakdown: int → Data type marks → Vari……
Program
Example
Explanation
return 0; }…
Program
Initially
Program
Later
இதனால் variable name same. ஆன……
Explanation
Program
int x = 10;…
Program
Step 1
Program
Step 2
Explanation
Old value 10 replaced by 20. ……
Program
Current
Program
So
Explanation
Final value: 25 VERY IMPORTAN……
Explanation
strange equation போல இருக்கும். Programm……
Explanation
Process: Right side first: x ……
Program
Final
Explanation
Variable naming rules
Variable name என்பது identifier. அதனால் identifier rules variables-க்கும் apply ஆகும். RULE 1: LETTER OR UNDE……
Explanation
Valid variable names
age marks student1 totalMarks……
Explanation
Invalid variable names
1age student mark total-mark ……
Explanation
Multiple variable declaration
Same data type variables ஒரே statement-ல் d……
Explanation
Multiple initialization
int a = 10, b = 20, c = 30;…
Definition
Meaning
a = 10 b = 20 c = 30…
Important
Important common confusion
Consider: int a, b = 10; இதன் meaning: a → declared, ……
Explanation
Variable with different data types
Integer variable int age = 25; Floating variable float weight = 65.5f; Double variable ……
Program
Program - different variables
Explanation
return 0; }…
Input
Input into variable
Program
Example
Explanation
return 0; } If user enters: 25…
Definition
Meaning
User enter செய்யும் value-ஐ age variable-ல் s……
Explanation
Variable in calculation
Variables calculations-ல் use செய்……
Dry Run
a = 10 b = 20 sum = a + b = 1……
Program
Program - addition
Explanation
return 0; }…
Explanation
Example
int x = 100; Conceptually mem……
x 100 Suppose later:…
Then: Variable Value x 200 Sa……
Explanation
Memory address
Every object/variable has a m……
Explanation
&x gives address of x.…
Output
Possible output
Exact address changes between……
prints: 10 But:…
Simple: x → Value &x → Address of x……
Explanation
Example
int marks = 90; marks is an identifier because it is a name. The named object represented by ……
Explanation
Valid. Constant const int x =……
Explanation
Invalid.…
Comparison
[VARIABLE vs LITERAL]…
Explanation
Example
int age = 25; age → Variable 25 → Literal Var……
Explanation
Local variable
Function அல்லது block-க்குள் ……
Program
Example
Explanation
x is local variable. Its scop……
Real Life Example
Local variable example
#include using namespace std;……
Explanation
Global variable
Functions-க்கு வெளியே declare……
Program
Example
Explanation
int x = 100;…
Explanation
return 0; } x is global variable. It can be accessibl……
Explanation
Scope
Scope என்பது variable name progr……
Program
Example
Program
Outside
Explanation
Invalid. Because x block scop……
Explanation
Block scope
{ int value = 100; cout…
Program
Example
Explanation
int x = 100;…
Explanation
return 0; }…
Local x global x-ஐ shadow செய்……
Here: x → Local variable ::x ……
Explanation
Static local variable
Normally local variable function call முடிந்ததும் lifeti……
Program
Example
Explanation
count++;…
Explanation
return 0; }…
Program
Normal
Every call: 1 Static: static in……
Explanation
Auto variable
Historically, ordinary local ……
Program
Example
Explanation
x is an automatic local variable. Modern C++-ல் auto keyword mostly type deduction-க்கு பயன்படுத்தப்படுகிறத……
Important
auto means type is automatica……
Explanation
Example
int x; Local automatic variable x has a……
Explanation
This can lead to undefined behavior f……
Practice
Initialization is good practice
Instead of: int total; Prefer when appropriate: int total = 0……
Explanation
Different initialization styles
C++ supports multiple forms. Copy initialization int x = 10; Direct initialization int x(10); List initializa……
Explanation
Reference variable
A reference acts as an alias fo……
Program
also changes
Explanation
return 0; }…
Because ref refers to x.…
Explanation
Pointer variable
Pointer variable stores another object's address. int x ……
Explanation
return 0; }…
*ptr accesses the value store……
Explanation
Variable lifetime
Scope and lifetime are related but different. S……
Program
Example
Explanation
x normally exists during exec……
Common Mistake
Common error 1
Using keyword as variable: int ……
Common Mistake
Common error 2
Number at beginning: int 10ma……
Common Mistake
Common error 3
Using variable before initial……
Common Mistake
Common error 4
Wrong data type: int percentage = 89.……
Common Mistake
Common error 5
Confusing assignment and comp……
Practice
Assignment
x = 10;…
Comparison
x == 10…
Remember
= → Assign == → Compare…
Common Mistake
Common error 6
Expecting both variables to initialize: int a, b = ……
Comparison
Variable vs Identifier vs Val……
Explanation
Example
int marks = 90;…
Important
A variable generally has
1. Name 2. Data type 3. Value……
Explanation
Example
int age = 25; Name → age Type → int Value → 25……
Remember
V = N T V M N → Name T → Type V → Value ……
TRB Point
What is a variable? A variable is a named memory ……
TRB Point
Trb point - important
Consider: int x = 10; Identify: int ……
MCQ
Which is a variable declarati……
Interview Point
Difference between declaration and initialization? Declaration: int ……
Interview Point
Difference between variable and constant? int……
Interview Point
Is an uninitialized local int……
Explanation
Example
int x; A local automatic fundamental variable does not automatically become zero.……
MCQ
A variable is:…
MCQ
Which is a valid declaration?…
MCQ
Which statement initializes x?…
MCQ
Which operator assigns a valu……
MCQ
Which variable name is invali……
MCQ
C++ variable names are:…
MCQ
What is the final value? int ……
MCQ
In: int a, b = 10; which vari……
MCQ
Which is a local variable? in……
MCQ
Which statement changes x fro……
Practice
Identify declaration, initialization, assignment: int x; x = 10; int y = 20; x ……
Dry Run
Practice - dry run
Summary
Variable A variable is a named memory locat……
Explanation
Syntax
data_type variable_name; int a……
Explanation
Main concepts: Declaration → int x; Initialization → int x = 10; Assignment → x = 20; Important d……
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