IMPLICIT ERROR

I am trying to write and read pin value from stm32 board, by using keil5 ARM, the problem i am facing is when i use pin8 in keil code it's showing some iplicit error.

const char pinsend[]= {C8_Pin,C9_Pin,C10_Pin,C11_Pin,C12_Pin,C13_Pin,C14_Pin,C15_Pin}; //ip C port

after C7_Pin declaration showing implicit error.

Thanks in Advance.