DLL export

for creating a DLL in VC++ 2005, what's the following do? is it a must
have?

#ifdef _USRDLL
#define EPGLIB_API __declspec( dllexport )
#else /* _USRDLL */
#define EPGLIB_API __declspec( dllimport )
#endif /* _USRDLL */
======================

for each function that' call by DLL user, I must add

PROJECTName_API + return type + PASCAL + functionName like follows?
why related to PSCAL??

EPGLIB_API BOOL PASCAL CreateEPGLibInstance();
EPGLIB_API HRESULT PASCAL LoadXMLData(LPCTSTR tszXMLFileName);
EPGLIB_API HRESULT PASCAL PostSoapRequest();

======================

// EPGLib.h : main header file for the EPGLib DLL
//

#pragma once

#ifndef __AFXWIN_H__
    #error "include 'stdafx.h' before including this file for PCH"
#endif

#include "resource.h" // main symbols

// CEPGLibApp
// See EPGLib.cpp for the implementation of this class
//

class CEPGLibApp : public CWinApp
{
public:
    CEPGLibApp();
    HRESULT LoadXMLData(LPCTSTR tszXMLFileName);

// Overrides
public:
    virtual BOOL InitInstance();
    virtual int ExitInstance();

    DECLARE_MESSAGE_MAP()
};

#ifdef _USRDLL
#define EPGLIB_API __declspec( dllexport )
#else /* _USRDLL */
#define EPGLIB_API __declspec( dllimport )
#endif /* _USRDLL */

EPGLIB_API BOOL PASCAL CreateEPGLibInstance();
EPGLIB_API HRESULT PASCAL LoadXMLData(LPCTSTR tszXMLFileName);
EPGLIB_API HRESULT PASCAL PostSoapRequest();