🔐 Caesar Cipher in C

This program implements the Caesar Cipher, a simple encryption technique where each letter in the plaintext is shifted by a fixed number of places in the alphabet.

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🚀 Programming Language

This program is written in C, making it efficient for handling string manipulations.

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🛠 Features

✅ Encryption and Decryption options
✅ Supports both uppercase & lowercase letters
✅ Input validation (ensures the key is between 0-25)
✅ User-friendly menu-driven program

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📌 How It Works

1. Encryption: Shifts each letter forward by a given key.
2. Decryption: Shifts each letter backward by the same key.
3. Only alphabetic characters are transformed, keeping spaces and punctuation unchanged.

Encryption Example with key==3

plaintext

HELLO

ciphertext

KHOOR

Decryption Example with key==3

ciphertext

KHOOR

Decrypted

HELLO

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📜 How to Run

1. Compile the program using a C compiler:

   gcc Caesar_Cipher.c -o cipher