add main function

main.c

@@ -54,3 +54,12 @@ void GPIOF_interruptHandler(void)            // Interrupt handler for GPIO Port
         GPIO_PORTF_ICR_R = 0x01;             // CLEAR INTERRUPT FLAG FOR SWITCH 1
     }
 }
+
+int main(void)                               // MAIN FUNCTION
+{
+    GPIO_PORT_F_init();                      // GPIO INITIALISATION FUNCTION
+    systick_setting();                       // SYSTICK SETUP
+    while (1)
+    {                                        // DO NOTHING
+    }
+}