BIOS Programming Language

The BIOS (Basic Input/Output System) is typically programmed using low-level languages because it interacts directly with hardware and needs to run before an operating system is loaded. The most common languages used for BIOS development are:

1. Assembly Language (x86 Assembly)

• Used for low-level hardware control and initialization.
• Essential for early boot stages before higher-level languages can be used.
• Example: BIOS interrupt calls (INT 13h for disk access, INT 10h for display control).

2. C Language

• Used for more complex parts of the BIOS after the system has initialized enough hardware to support C execution.
• Provides better readability and maintainability compared to Assembly.
• Most modern BIOS/UEFI firmware is written in C.

3. UEFI BIOS – C and Assembly

• Modern BIOS implementations use UEFI (Unified Extensible Firmware Interface) instead of traditional BIOS.
• UEFI is primarily written in C with some Assembly for low-level hardware setup.
• It follows the UEFI specification, which is typically implemented using EDK2 (EFI Development Kit 2), an open-source UEFI firmware development environment.

4. Scripting Languages for BIOS Configuration

• Python, Perl, and Lua are sometimes used for BIOS testing and configuration automation.
• Not used in the BIOS firmware itself but for development and debugging purposes.

Firmware Development Tools

• TianoCore (EDK2): Open-source implementation of UEFI firmware.
• GCC, LLVM/Clang, and Microsoft Visual Studio: Common compilers used for UEFI firmware development.

In summary, traditional BIOS firmware is mainly written in Assembly and C, while modern UEFI firmware is almost entirely written in C with minimal Assembly for early-stage initialization.