error LNK2001 when compiling under VS 6.0

Project_Library.obj : error LNK2001: unresolved external symbol "void __cdecl S_VAL_S(char,struct Options *)" (?S_VAL_S@@YAXDPAUOptions@@@Z)
Project_Library.obj : error LNK2001: unresolved external symbol "void __cdecl S_VAL_I(char,struct Options *)" (?S_VAL_I@@YAXDPAUOptions@@@Z)
Project_Library.obj : error LNK2001: unresolved external symbol "void __cdecl S_FLAG(char)" (?S_FLAG@@YAXD@Z)
Debug/Project_1.exe : fatal error LNK1120: 3 unresolved externals
Error executing link.exe.

////////////////////////////////////////////////////
//proj_lib.h
////////////////////////////////////////////////////
#ifndef PROJ_LIB_H
#define PROJ_LIB_H

#include "main.h"

void CLAP(int count, char** value, struct Options *);	// Command Line Argument Process
void CLAE();					// Command Line Argument Error

void S_FLAG(char tag);				// Single Character Check/Change State Function

void S_VAL_I(char tag, struct Options *);		// Single Character Value(int) Function
void S_VAL_S(char tag, struct Options *);		// Single Character Value(string) Function

void W_FLAG(char tag);				// Word Check/Change State Function

void W_VAL_I(char* tag, int i_param);			// Word Value(int) Function
void W_VAL_S(char* tag, string s_param);		// Word Value(string) Function

#endif

////////////////////////////////////////////////////
//proj_lib.cpp
////////////////////////////////////////////////////
#include "proj_lib.h"

// COMMAND LINE ARGUMENT PROCESS
// parses command line arguments passed from main function
// and determines appropriate secondary function(s) to call
void CLAP(int count, char** value, struct Options * p_opt)
{

	// Determine if command line has proper number of arguments or call CLAE()
	if ( (count < MIN) || (count > MAX) )
	{
		CLAE();
	}


	// Loop through all arguments on command line
	for (int i = 1; i < count; i++)

		// Determine if command line beings with '-' or '--' and has unary
		// or binary arguments, then call appropriate secondary function
		if ( (value[i][0] == '-') && (strlen (value[i]) == 2) )
		{
			// if # of args is = to current index then call S_FLAG
			if ( count == i )
			{
				S_FLAG(value[i][1]);
			}

			// if # of args is > current index & the first char
			// value of next index = '-' then call S_FLAG
			else if ( (count > i) && (value[i + 1][0] = '-') )
			{
				S_FLAG(value[i][1]);
			}

			// if # of args is > current index & the first char
			// value of next index != '-' then call S_VAL
			else if ( (value[i][0] == '-') && (value[i + 1][0] != '-') )
			{

				// if next index char value is numeric, convert to integer
				// and call S_VAL using integer conversion as 2nd parameter
				p_opt->s_param = *(value[i + 1]);
				p_opt->i_param = atoi(p_opt->s_param.c_str());

				if ( p_opt->i_param != NULL)
				{
					S_VAL_I(*(value[i + 1]), p_opt);
				}

				else
				{
					S_VAL_S(*(value[i + 1]), p_opt);
				}
			}
		}

	// other misc. code
}


// COMMAND LINE ARGUMENT ERROR
// displays an error message and usage syntax, then exits
void CLAE()
{
	// Display error & usage messages
	cout << "*** ERROR ***" << endl << endl;
	cout << "Usage: filename [-option]/[--option] {numeric/integer value}" << endl << endl;
	cout << "Please use [-h]/[--help] to display list of acceptable options" << endl << endl;

	// Exit program
	exit(-1);
}


// SINGLE CHARACTER CHECK/CHANGE STATE FUNCTION
// sets or clears (make true or false) variable which
// corresponds to the TAG value passed from command line
void S_FLAG(char* tag)
{
	// compare tag value(s) against list of changeable options and then
	// process changes based upon predefined choices of customization

	 cout << *tag << endl;
}


// SINGLE CHARACTER VALUE FUNCTION (int)
// accepts a numeric parameter and sets the variable associated
// with that specific option TAG equal to the parameter value
void S_VAL_I(char* tag, struct Options * p_opt)
{
	// set variable equal to parameter value
		 cout << *tag << p_opt->i_param << endl;
}


// SINGLE CHARACTER VALUE FUNCTION (string)
// accepts a string parameter and sets the variable associated
// with that specific option TAG equal to the parameter value
void S_VAL_S(char* tag, struct Options * p_opt)
{
	// set variable equal to parameter value
		 cout << *tag << p_opt->s_param << endl;
}

	// other misc. code
}