How should I describe in C language to access data of a specific address?
Declare the address you want to use (with a volatile declaration) and assign a name.
For example, assume that address 10000H consists of 8-bit data and its name is PORT1.
In this case, declare as:
#define PORT1 *((volatile unsigned char *) 0x10000)
You can access this address by:
PORT1 = 0x5;