Conceptually, the C library can be divided into functions that are part of the ISO C standard (for example printf()) and functions that provide support to the ISO C standard.

For example, Figure 1 shows the C library implementing the function printf() by writing to the debugger console window. This implementation is provided by calling _sys_write(), a support function that executes a semihosting call, resulting in the default behavior using the debugger instead of target peripherals.