Using Keil's own RTL under STM32

Keil ARTX (Advanced Real-Time eXecutive) is a small real-time operating system provided by Keil for the ARM series, integrated into its UV3 development environment. After downloading and installing the RealView MDK personal learning version, ARTX is also installed in the C:KeilARMRLRTX directory. There are STM32 example programs in the C:KeilARMBoardsKeilMCBSTM32STLIB_RTX_Blinky directory. After simple modification, it runs on the Wanli development board.
#include
#include
OS_TID t_phaseA; //Assign task ID number
OS_TID t_phaseB;
OS_TID t_phaseC;
OS_TID t_phaseD;

#define LED_A GPIO_Pin_4
#define LED_B GPIO_Pin_5
#define LED_C GPIO_Pin_6
#define LED_D GPIO_Pin_7
#define LED_On(led) GPIO_SetBits(GPIOC , led)
#define LED_Off(led) GPIO_ResetBits(GPIOC, led)

extern void SetupClock (void);
extern void SetupLED (void);


void phaseA (void) __task {
for (;;) {
LED_On (LED_A);
os_dly_wait (100);
LED_Off(LED_A);
os_dly_wait (100);
}
}

void phaseB (vo id) __task {
for (;;) {
LED_On (LED_B);
os_dly_wait (100);
LED_Off(LED_B);
os_dly_wait (100);
}
}

void phaseC (void) __task {
for (;;) {
LED_On (LED_C);
os_dly_wait (100);
LED_Off(LED_C);
os_dly_wait (1 00);
}
} void

phaseD (void) __task {
for (;;) {
LED_On (LED_D);
os_dly_wait (100);
LED_Off(LED_D);
os_dly_wait (100);
}
}

void init (void) __task {
t_phaseA = os_tsk_create (phaseA, 0);
os_dly_wait (50);
t_phaseB = os_tsk_create (phaseB, 0);
os_dly_wait (50);
t_phaseC = os_tsk_create (phaseC, 0);
os_dly_wait (50);
t_phaseD = os_tsk_create (phaseD, 0);
os_tsk_delete_self ();
}

int main (void) {
SetupClock();
SetupLED ();
os_sys_init (init);
}
After the initialization, os_sys_init (init) starts the initialization task. In the initialization task, 4 tasks are started one after another. After starting,

Delete the initialization task. These four tasks each control the switch of an LED.

============================================

Personal understanding:

int main(void)

{

         os_sys_init_user( TaskMain,               

                            50,

                            TaskSysInitStack,

                            SysInitTaskStakSize );

         while(1); 

}

Question 1: Why don't we call the os_sys_init_user() API after creating many small tasks in TaskMain? The reason is that after initializing TaskMain, it does not return, so it cannot execute the while statement below  .

Q2: TaskMain creates small tasks, and each small task has a while(1) infinite loop, which is the concept of multithreading. Except for while(1), all other functions are executed only once, including the variables in the main function and small tasks. Only while(1) runs with time slices and priorities, realizing multithreaded execution.