Overview
A freestanding x86_64 operating system written from scratch in Rust that boots straight into a working calculator - no Linux underneath, no std, no heap. Hand-written VGA text-mode driver writing directly to physical memory at 0xb8000 with a box-drawn keypad UI, polled PS/2 drivers for both keyboard (scancode set 1, shift and extended codes) and mouse (3-byte packets decoded into a pointer overlay), port I/O through inline assembly, a recursive-descent expression parser with operator precedence over software-emulated f64, and fixed-capacity stack strings standing in for String. Buttons are driven by keyboard, arrow-key cursor or mouse click through a single shared code path. Boots in QEMU and on real hardware.