TC中出现Linker Error: Undefined symbol

#include <stdio.h>
#include <conio.h>
#include <dos.h>
#include <stdlib.h>
#include <graphics.h>
typedef unsigned char BYTE;
typedef unsigned int WORD;
typedef unsigned long DWORD;
/* PCI设备索引。bus/dev/func 共16位，为了方便处理可放在一个WORD中 */
#define PDI_BUS_SHIFT 8
#define PDI_BUS_SIZE 8
#define PDI_BUS_MAX 0xFF
#define PDI_BUS_MASK 0xFF00
#define PDI_DEVICE_SHIFT 3
#define PDI_DEVICE_SIZE 5
#define PDI_DEVICE_MAX 0x1F
#define PDI_DEVICE_MASK 0x00F8
#define PDI_FUNCTION_SHIFT 0
#define PDI_FUNCTION_SIZE 3
#define PDI_FUNCTION_MAX 0x7
#define PDI_FUNCTION_MASK 0x0007
#define MK_PDI(bus,dev,func) (WORD)((bus&PDI_BUS_MAX)<<PDI_BUS_SHIFT | (dev&PDI_DEVICE_MAX)<<PDI_DEVICE_SHIFT | (func&PDI_FUNCTION_MAX) )
/* PCI配置空间寄存器 */
#define PCI_CONFIG_ADDRESS 0xCF8
#define PCI_CONFIG_DATA 0xCFC