I am teaching students presently on ARM Micro 4 assembly language programming. I want to know if we can call C functions like printf functions . how to call inline C functions from assembly functions? I have written a code in assembly for systick timer to operate with systick timer interrupt handler in assembly language programming. I am able to get the timer counter running, but i am not able to get into the interrupt handler routine. please help me how to enter. i am attaching the main program file. please guide me how to enable the systick timer interrupt and make the code work. my platform is the ARM M4 from ST micro stm 32 nucleo board with the STM32F401RE controller. if possible request you to provide a code to stsrt the systick timer in assembly language program for this controller board please help me resolve the issue.