The ARM C libraries support multithreading, for example, where you are using a Real Time Operating System (RTOS). When describing multithreading in the rest of this section, the following definitions are used:

If there are multiple processes on a machine, they can be entirely separate and do not share any data (except under unusual circumstances). Similarly, each process might be a single-threaded process or might be divided into multiple threads.

Where you have single-threaded processes, there is only one flow of control. In multithreaded applications, however, several flows of control might try to access the same functions, and the same resources, concurrently. To protect the integrity of resources, any code you write for multithreaded applications must be reentrant and thread-safe.

This section contains information to help you write multithreaded applications: