BleepingComputer.com: want to understand

I need that someone help me and comment the following code to me exactly. even i learned many tutorials of c++ but i still need help because it's so complicated to me. all i want that some one explain to me with comments every step.thanks for your help
#if defined(_MSC_VER)
#pragma warning ( disable : 4786 )
#endif

#ifdef __BORLANDC__
#define ITK_LEAN_AND_MEAN
#endif
#include "itkHessian3DToVesselnessMeasureImageFilter.h"
#include "itkHessianRecursiveGaussianImageFilter.h"
#include "itkSymmetricSecondRankTensor.h"
#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"

int main( int argc, char *argv[] )
{

if( argc < 3 )
{
std::cerr << "Usage: inputImage outputImage [sigma] [alpha_1] [alpha_2]" << std::endl;return EXIT_FAILURE;
}

const unsigned int Dimension = 3;
typedef double InputPixelType;
typedef float OutputPixelType;

typedef itk::Image< InputPixelType, Dimension > InputImageType;
typedef itk::Image< OutputPixelType, Dimension > OutputImageType;

typedef itk::HessianRecursiveGaussianImageFilter<
InputImageType > HessianFilterType;
typedef itk::Hessian3DToVesselnessMeasureImageFilter<
OutputPixelType > VesselnessMeasureFilterType;
typedef itk::ImageFileReader< InputImageType > ReaderType;
typedef itk::ImageFileWriter< OutputImageType > WriterType;

HessianFilterType::Pointer hessianFilter = HessianFilterType::New();
VesselnessMeasureFilterType::Pointer vesselnessFilter =
VesselnessMeasureFilterType::New();

ReaderType::Pointer reader = ReaderType::New();
WriterType::Pointer writer = WriterType::New();

reader->SetFileName( argv[1] );
hessianFilter->SetInput( reader->GetOutput() );
if( argc >= 4 )
{
hessianFilter->SetSigma( static_cast< double >(atof(argv[3])) );
}
vesselnessFilter->SetInput( hessianFilter->GetOutput() );
writer->SetInput( vesselnessFilter->GetOutput() );
writer->SetFileName( argv[2] );
if( argc >= 5 )
{
vesselnessFilter->SetAlpha1( static_cast< double >(atof(argv[4])));
}
if( argc >= 6 )
{
vesselnessFilter->SetAlpha2( static_cast< double >(atof(argv[5])));
}

writer->Update();
return EXIT_SUCCESS;
}

Thanks again

1. That code depends on external libraries we do not have. If you ask questions about libraries, you have to include them.
2. We do not do homework.

You need to start with a simpler example anyway before jumping into a rats nest of code.....

Billy3