How to use Gdal on Visual Studio 2012 c++

Hai All, 

My target just know want to try to display raster map, but i still stuck in 
this starting point. The code I run below will display an error 

error c4700 uninitialized local variable ‘pszFilename’ used 

can someone help me regarding this and what i need to with the file i 
download from this link:https://trac.osgeo.org/gdal/wiki/DownloadSource

where i need to add on VS2012? 

Thank you and best regards 

#include “gdal_priv.h” 
#include “cpl_conv.h” // for CPLMalloc() 
#include “stdafx.h” 
#include “gdal.h” 

int main() 

        class GDALDataset; 
        const char *pszFilename; 
        

    GDALDataset *poDataset; 
        void CPL_DLL CPL_STDCALL GDALAllRegister(void); 

    poDataset = (GDALDataset *) GDALOpen(pszFilename, GA_ReadOnly ); 
    if( poDataset == NULL ) 
        {}