CMSIS ::Device:Startup

In actual file names, <device> is the name of the microcontroller device.

startup_<device>.s   file with reset handler and exception vectors

system_<device>.c   configuration file for basic device setup (clock and memory BUS)

<device>.h                include file for user code access to the microcontroller device.

The <device>.h header file is included in C source files and defines:

 Peripheral Access with standardized register layout.
 Access to Interrupts and Exceptions and the Nested Interrupt Vector Controller (NVIC).
 Intrinsic Functions to generate special instructions, for example to activate sleep mode.
 Systick Timer (SYSTICK) functions to configure and start a periodic timer interrupt.
 Debug Access for printf-style I/O and ITM communication via on-chip CoreSight.

mdk5-getting-started