Zilch

This repository documents an attempt at bootstrapping a cold silicon baby with nothing more than a BIOS and a floppy drive into a mean lean calculating machine.

Prerequisites

• nasm
• make
• qemu
• od

Contents

Each step in the bootstrapping process is within its own directory.

00-hi

This example consists of an assembly snippet which uses BIOS interrupts to display the characters "Hi" onto the screen.

• Run make to produce a real mode bootloader binary, and a floppy image containing that bootloader.

• Run make run to spin up an i386 qemu virtual machine with the floppy image attached and selected as the boot drive. This will produce the message "Hi" onto the screen, provided to you by the BIOS :)

---

This directory also holds a subdirectory with the same code, but without it being a boot sector. Running make here will produce a hi.txt file, the contents of which are the octal code, which we use in the next step.

This is here mainly to document how we can generate octal code which we can input as code through the BIOS' real mode.

01-simple-monitor

This is where the fun begins.

In here you will find a simple monitor written in the same assembly, utilising the BIOS to input code in octal and load that into memory for later execution.

This monitor can now be used to type out a better monitor with more functionality.

For now though, we will use it to display the message "Hi" again.

• Run make to build the binary and floppy image.

• Run make run to run a VM with the floppy image as the boot drive.

• Very carefully type out the following octal code (just the digits, no spaces) using your keyboard.

  264 016 260 110 315 020 264 016 260 151 315 020 364
  

• To end a programme input, just type an invalid digit (anything > 7). This will end the input sequence, and execute your input. In this case, displaying "Hi" on the screen.