Engineering the Core: The Gramado OS Journey

Most developers use operating systems—very few build them. Gramado OS is a rare and ambitious "Hobbyist" project that explores the fundamental architecture of a modern 64-bit operating system for x86_64. Starting in 2005 with a simple bootloader, the developer has painstakingly built a custom kernel and initial user-mode applications, providing a clean-slate environment to study Low-Level System Design.

Architecture: Beyond the BIOS

Gramado OS is engineered to interact directly with the hardware:

• 64-Bit Memory Management: Unlike 32-bit legacy systems, Gramado is designed to harness the full address space of modern x86_64 processors, allowing for sophisticated memory protection and paging.
• Tailored Bootloader: The project includes a custom-coded bootloader that transitions the CPU from "Real Mode" to "Long Mode" (64-bit), setting the stage for the kernel to take command.
• Monolithic Kernel Approach: The kernel manages the essential services—interrupts, basic I/O, and process scheduling—entirely from scratch, avoiding the Bloatware found in mainstream OSs.

The Developer's Toolkit: GCC and NASM

Building an OS requires a specialized toolchain:

1. Cross-Compilation: The project uses GCC to compile C code into binary formats that can run without an underlying host OS.
2. Assembly Mastery: For critical tasks like context switching or hardware interrupts, the developer utilizes NASM (Netwide Assembler) to write performance-critical machine instructions.
3. Virtual Validation: While it can run on real hardware, Gramado is frequently tested using QEMU, allowing for safe experimentation with system-level code without risking a physical machine.

Why Build an Operating System?

For many, OS development is the "Final Boss" of computer science. By studying Gramado OS, you gain a deep understanding of:

• How the CPU manages Context Switching.
• The relationship between User Mode and Kernel Mode.
• The physics of Interrupt Requests (IRQ) and hardware drivers.

Gramado OS stands as a testament to the power of long-term hobbyist passion, proving that with enough time and curiosity, one person can build the very heart of computing.

Gramado is a 64-bit operating system for the x86_64 architecture. Created as a labor of love starting in 2005, it has evolved from a simple bootloader into a functional kernel and suite of user-mode apps, offering a unique window into the mechanics of modern computing.