rotOS

Barebones Kernel (4/16)

Features & Recent Changes

Kernel & Terminal

• VGA text output with colored text, scrolling, and basic terminal emulation.
• term_putchar now uses a switch statement for extensible control character handling (newline, backspace, etc).
• Backspace (\b) support: erases the previous character on screen.
• Easily extensible for more control characters (tab, carriage return, etc).

Interrupts & IRQs

• Full IDT setup (idt_install) and PIC remapping.
• Clean separation of ISRs (CPU exceptions) and IRQs (hardware interrupts).
• IRQ handlers can be registered per line; unhandled IRQs print their number in decimal.
• Assembly stubs fixed to pass correct register state to C handlers.

Drivers

• Timer: PIT initialized to 100 Hz; handler increments a tick counter (ready for scheduling).
• Keyboard: Basic US QWERTY layout, prints characters to terminal, supports Enter, Backspace, Tab. Keyboard buffer can be extended for line editing.

Build System

• scripts/linux-build.sh compiles all drivers, kernel, and interrupt code, links to ELF, and produces a bootable image.
• Automatically calculates kernel size for MBR.

Bug Fixes

• Fixed IRQ handler pointer bug: now receives correct IRQ numbers (0-15).
• Backspace no longer prints a dot; instead, it erases as expected.
• Improved error messages for unhandled IRQs.

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How to Build and Run

1. Set your current directory to rotOS

2. Make scripts executable:

sudo chmod +x ./scripts/*.sh

3. Install cross tools (if needed):

sudo ./scripts/linux-tools.sh

4. Build the OS:

sudo ./scripts/linux-build.sh

5. Run in QEMU:

sudo qemu-system-x86_64 os-image.bin

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Expected Output

The emulator should display:

Welcome to rotOS!
System initialized successfully.
Terminal is ready.
Memory initialized.
Interrupts installed.
Timer initialized (100 Hz).
Keyboard initialized.
Interrupts enabled. Type something!

You should be able to type on the keyboard and see characters echo, with working backspace.

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Directory Structure

• kernel.c — Kernel entry, terminal, and core logic
• kernel_entry.asm - Kernel entry point (assembly)
• drivers/ — Keyboard and timer drivers
• interrupt/ — IDT, ISR, IRQ, and low-level interrupt logic
• scripts/ — Build scripts
• bootloader/ — MBR and boot sector code
• build/ — Output binaries (after build)

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Notes

• The kernel is modular and ready for further extension: paging, scheduler, advanced terminal, etc.
• For debugging, unhandled IRQs will print their IRQ number.
• See code comments for extension points and TODOs.