Rt0

rt0 is a term used in various software contexts to refer to the initial runtime bootstrap component or the first task in an execution environment. It is not a single standardized entity, but rather a name that appears in different toolchains and platforms with related but distinct roles.

In generic C/C++ development on Unix-like systems, startup code often involves objects such as crt0.o, crt1.o, and related startup files. In some toolchains, a variant named rt0 may serve as the program’s entry point, setting up the runtime environment, arranging the program’s arguments and environment, initializing the C runtime library, and invoking main. It may also trigger global constructors (in C++) before main and run destructors after main returns. The exact behavior and file naming can vary by architecture and compiler, so rt0 is not universally defined as a single standardized file.

In embedded and real-time operating system contexts, rt0 can denote the initial or root task that runs when the system starts. This rt0 task is typically responsible for low-level hardware initialization, clock and memory setup, driver initialization, and the creation of other tasks before starting the scheduler. In such environments, rt0 serves as a bootstrap routine that hands control to higher-level application logic or to the RTOS task scheduler.

Because rt0’s meaning is context-dependent, its specific responsibilities are described in platform or project documentation rather than a universal specification. Common related references include crt0 and the broader C runtime startup sequence, as well as any platform-specific bootstrap code or startup assembly files.