I suppose it is "CyPins_SetPin(Pin_1);" to set your monitor-output.
Open the file Pin_1_aliases.h. You will see the macro for pin configuration register. It will be as below.
#define Pin_1_0 Pin_1__0__PC
Therfore use API as below to set this pin high.
You can use your method without using any macros and use original register names as mentioned in cydevice_trm.h.
Note that you used "PC0" which means port 1 and pin 0 but your pin is placed at P1, therfore you should use PC5.
Thanks for your friendly reply! and i can solve my problem as soon as possible!