📘 VDOS Step 03 – Minimal Shell + Keyboard Input

📌 Purpose

This step adds the ability for user interaction by:

• Displaying a welcome screen
• Capturing user keystrokes
• Echoing typed characters

🧬 Technologies Used

• Real Mode (16-bit x86)
• BIOS interrupts:
  • int 10h for screen output
  • int 16h for keyboard input

🧠 Instruction Flow

1. Start at memory 0x7C00
2. Print welcome message using BIOS text output
3. Enter a loop to wait for and echo keyboard input
4. Continues infinitely like a primitive shell

🛠 Instructions to Test

nasm -f bin shell.asm -o shell.img
qemu-system-x86_64 -drive format=raw,file=shell.img

🧾 Output Example

🔷 Welcome to VDOS Shell
Type anything:
> VDOS is awesome!

🔍 What We Learn

• Keyboard I/O at BIOS level
• How primitive OSes accepted user input
• Fundamentals of command shells

⏭ Next

→ Add parsing logic → Display responses for commands like help, ver, clear → Prepare for file access