Unseccessful Header file (.h) creation, what's wrong?

I wrote a Program (pro87.c), it works fine.  Then I separated it into two files as a Header (pro86.h) and a Program (pro86.c).  It turned error during making.  Compiler  said "Linker Error: Undifined symbol _main in module c0.ASM.   What's wrong.  It's exactly the same except as two files.

Here is as a single file.  It's O.K.
/*PROGRAM pro87.c */
/* DataBase type determination */
#include<stdio.h>
#include<string.h>
#define UNKNOWN      1   //"Unknown"   /* Data format type */
#define GENBANK 2   //"GenBank"
#define EMBL      3   //"EMBL"
#define PIR            4   //"PIR"
#define PRF            5   //"PRF"
#define SEQDATA 6   //"SeqData"
#define BUFLEN  256   /* maximum length of buffer for string */

char linebuf[BUFLEN];

main(int argc, char *argv[])
{
   int dataType;
   FILE *fp;
   if(argc!=2)
        printf("Usage : pro86 filename\n");
   else
        fp=fopen(argv[1], "r");

   dataType=0;
   while(fgets(linebuf, BUFLEN, fp)!=NULL)
   {
       if (strncmp(linebuf, "LOCUS", 5)==0){
            dataType = GENBANK;      break;
       }else if (strncmp(linebuf, "ID ", 3)==0){
            dataType = EMBL; break;
       }else if (strncmp(linebuf, "ENTRY", 5)==0){
            dataType = PIR;      break;
       }else if (strncmp(linebuf, "CODE", 4)==0){
            dataType = PRF; break;
       }else if (linebuf[0] == '>'){
            dataType = SEQDATA; break;
       }else
            dataType = UNKNOWN;
   }

   if(dataType==1)
        printf("Unknown\n");
   if(dataType==2)
        printf("GenBank\n");
   if(dataType==3)
        printf("EMBL\n");
   if(dataType==4)
        printf("PIR\n");
   if(dataType==5)
        printf("PRF\n");
   if(dataType==6)
        printf("SeqData\n");
   fclose(fp);
   return 0;
}

_______________________________________________________
The above is OK, now separate it to two files.

/* pro86.H  ;   This is a header file. */
/* Data format type */
#define UNKNOWN      1   //"Unknown"
#define GENBANK 2   //"GenBank"
#define EMBL      3   //"EMBL"
#define PIR            4   //"PIR"
#define PRF            5   //"PRF"
#define SEQDATA 6   //"SeqData"
_______________________________________
AND
/* PROGRAM Pro86.c */
/* DataBase type determination */
#include<stdio.h>
#include<string.h>
#include<pro86.h>
#define BUFLEN  256   /* maximum length of buffer*/

char linebuf[BUFLEN];

main(int argc, char *argv[])
{
   int dataType;
   FILE *fp;
   if(argc!=2)
        printf("Usage : pro86 filename\n");
   else
        fp=fopen(argv[1], "r");

   dataType=0;
   while(fgets(linebuf, BUFLEN, fp)!=NULL)
   {
       if (strncmp(linebuf, "LOCUS", 5)==0){
            dataType = GENBANK;      break;
       }else if (strncmp(linebuf, "ID ", 3)==0){
            dataType = EMBL; break;
       }else if (strncmp(linebuf, "ENTRY", 5)==0){
            dataType = PIR;      break;
       }else if (strncmp(linebuf, "CODE", 4)==0){
            dataType = PRF; break;
       }else if (linebuf[0] == '>'){
            dataType = SEQDATA; break;
       }else
            dataType = UNKNOWN;
   }

   if(dataType==1)
        printf("Unknown\n");
   if(dataType==2)
        printf("GenBank\n");
   if(dataType==3)
        printf("EMBL\n");
   if(dataType==4)
        printf("PIR\n");
   if(dataType==5)
        printf("PRF\n");
   if(dataType==6)
        printf("SeqData\n");
   fclose(fp);
   return 0;
}
__________________________________________
These don't compile.  Linker Error!!  Help me.