Callback function,

Callback function,

 1 #include <stdio.h>   2    3 void PrintNum1(int n); 4 void PrintNum2(int n); 5 void ShowNum(int n, void (* ptr)(int));   6    7 void PrintMessage1();   8 void PrintMessage2();   9 void PrintMessage3();  10 void ShowMessage(void (* ptr)());  11   12 int main(){  13    ShowNum(11111, PrintNum1);  14    ShowNum(22222, PrintNum2);  15    ShowMessage(PrintMessage1);  16    ShowMessage(PrintMessage2);  17    ShowMessage(PrintMessage3);  18 }  19   20 void PrintNum1(int n){  21    printf("Test1 is called,the number is %d\n", n);  22 }23 24 void PrintNum2(int n){  25    printf("Test2 is called,the number is %d\n", n);  26 }   27   28 void ShowNum(int n, void (* ptr)()){  29    (* ptr)(n);  30 }  31   32   33 void PrintMessage1(){  34    printf("This is the message 1!\n");  35 }  36   37 void PrintMessage2(){  38    printf("This is the message 2!\n");  39 }  40   41 void PrintMessage3(){  42    printf("This is the message 3!\n");  43 }  44   45 void ShowMessage(void (* ptr)()){  46     (* ptr)();  47 }