Caesar Cipher

Project Overview

This project is part of The Odin Project curriculum. It implements a Caesar Cipher, a simple encryption technique where each letter in a string is shifted a certain number of places down the alphabet.

For example:

Original: Hello
Shift: 5
Encrypted: Mjqqt

Non-letter characters like spaces, punctuation, and numbers are left unchanged.

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Features

• Encrypts both uppercase and lowercase letters
• Handles wrap-around (e.g., "z" → "a")
• Preserves non-alphabetic characters
• Written in Ruby using basic string and ASCII manipulation

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How It Works

1. Loop through each character in the input string.
2. Check if the character is a letter.
3. Determine if it’s uppercase or lowercase to use the correct alphabet base (A or a).
4. Convert the letter to its alphabet position (0–25).
5. Add the shift amount and wrap around using modulo 26.
6. Convert the shifted position back to a letter.
7. If the character is not a letter, keep it unchanged.
8. Return the new encrypted string.

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Usage

# Call the Caesar cipher method with a string and a shift value
puts caesar_cipher("Hello, World!", 5)
# Output: Mjqqt, Btwqi!

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Learning Points

• Working with ASCII codes using .ord and .chr
• Using modulo arithmetic to handle wrap-around
• Handling uppercase and lowercase letters separately
• Preserving non-letter characters
• Structuring a method in Ruby with clean loops and conditional logic