Variables & Constants in C

 

💻 Variables & Constants in C (Easy English Explanation)

This is a very important basic concept in C programming 📚
If you understand this, coding becomes much easier 🚀

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🔹 1. Variables in C 🏷️

A variable is a container used to store data.
👉 Its value can change during program execution.

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✅ Example

int a = 10;

👉 Here:

• int → data type
• a → variable name
• 10 → value

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🔹 Real-Life Example 🤔

Think of a variable like a box 📦

• You can put something inside
• You can change it anytime

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🔹 Types of Variables

1. Integer Variable

int age = 20;

2. Float Variable

float price = 99.5;

3. Character Variable

char grade = 'A';

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🔹 Rules for Variables ⚠️

✔ Must start with a letter or _
✔ Cannot contain spaces
✔ Cannot be a keyword
✔ Case-sensitive (a and A are different)

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🔹 2. Constants in C 🔒

A constant is a value that cannot be changed once assigned.

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✅ Example

const int x = 10;

👉 Now, the value of x cannot be changed

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🔹 Types of Constants

1. Integer Constant

10, -5, 100

2. Floating Constant

3.14, 0.5

3. Character Constant

'A', 'B'

4. String Constant

"Hello"

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🔹 Real-Life Example 🤔

Think of a constant like a fixed rule 📜

• Once set, it cannot change

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🔹 Difference: Variables vs Constants 🆚

Feature	Variables 🏷️	Constants 🔒
Value	Can change	Cannot change
Use	For changing data	For fixed data
Example	int a = 10;	const int a = 10;

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🔹 Example Program 🧠

#include <stdio.h>

int main() {
    int a = 10;        // variable
    const int b = 20;  // constant

    a = 15;   // allowed
    // b = 25; ❌ not allowed

    printf("%d %d", a, b);
    return 0;
}

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🔹 Final Concept 🔥

👉 Variable = value can change
👉 Constant = value is fixed

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📝 Summary

• Variables store data that can change 📦
• Constants store fixed data 🔒
• Both are used to manage data in programs