Miracle C output問題

There is no problem. If you are compiling with most C compilers, the output window is closed at the end of the execution, which is normally quite short, to the extent that you do not see the output.
All you need to do is to insert at the end of the program a statement that requires user input, like scanf(...), or system("pause");
This will halt the exit of the screen and allows you to view the output.

2009-03-23 04:41:51 補充：
With the information that you gave, it is hard to pin-point the problem, because I don't get to know if your window disappeared or not.
A normal compiler should print something with:
#include stdio...
void main(){printf("HELLO!\n"); system("pause");}

2009-03-23 04:42:01 補充：
You could also try forcing to display using:
fflush(stdout);
after the print statement.
If that still does not work, you may want to check your compiler or configurations.
Finally, check if you have a loop in your program so the print statement never got executed.