Вот пример:

Файл .h для dll

#ifndef _DLLTEST_H_
#define _DLLTEST_H_

#include <iostream.h>
#include <stdio.h>
#include <windows.h>

extern "C" __declspec(dllexport) void NumberList();
extern "C" __declspec(dllexport) void LetterList();


#endif
//___________________________________________
Файл .cpp для dll

#include "dlltest.h"

#define MAXMODULE 50

char module[MAXMODULE];



extern "C" __declspec(dllexport)

void NumberList() {

GetModuleFileName(NULL, (LPTSTR)module, MAXMODULE);

cout << "\n\nThis function was called from "
<< module
<< endl << endl;

cout << "NumberList(): ";


for(int i=0; i<10; i++) {

cout << i << " ";
}

cout << endl << endl;
}



extern "C" __declspec(dllexport)

void LetterList() {

GetModuleFileName(NULL, (LPTSTR)module, MAXMODULE);

cout << "\n\nThis function was called from "
<< module
<< endl << endl;

cout << "LetterList(): ";


for(int i=0; i<26; i++) {

cout << char(97 + i) << " ";
}

cout << endl << endl;
}
//___________________________________________
Файл cpp в котором вызымаешь функции из dll'ки
#include <windows.h>
#include <iostream.h>
#include <stdio.h>
#include <conio.h>

#define MAXMODULE 50

typedef void (WINAPI*cfunc)();

cfunc NumberList;
cfunc LetterList;

void main() {

HINSTANCE hLib=LoadLibrary("DLLTEST.DLL");


if(hLib==NULL) {

cout << "Unable to load library!" << endl;
getch();
return;
}

char mod[MAXMODULE];

GetModuleFileName((HMODULE)hLib, (LPTSTR)mod, MAXMODULE);
cout << "Library loaded: " << mod << endl;


NumberList=(cfunc)GetProcAddress((HMODULE)hLib, "NumberList");
LetterList=(cfunc)GetProcAddress((HMODULE)hLib, "LetterList");

if((NumberList==NULL) || (LetterList==NULL)) {

cout << "Unable to load function(s)." << endl;
FreeLibrary((HMODULE)hLib);
return;
}

NumberList();
LetterList();

FreeLibrary((HMODULE)hLib);

getch();
}