帮我看看这几行干什么用的？

const char szOpenFilter[256]="(*.txt)|*.txt||";
const char szCurrentOpPath[256]="CurrentOpPath";
const char szEnviromentSection[256]="Enviroment";
const char szOpenFiltertxt[256]="(*.txt)|*.txt||"; CFileDialog *pFileSave=new CFileDialog(FALSE, ".txt", NULL,
OFN_EXPLORER|OFN_FILEMUSTEXIST, szOpenFiltertxt,this);
CString strInitDir1 = ::AfxGetApp()->GetProfileString(szEnviromentSection,szCurrentOpPath,"d:\\");
pFileSave->m_ofn.lpstrInitialDir = strInitDir1.GetBuffer(10);
strInitDir1.ReleaseBuffer(); FILE *fp1;
if( pFileSave->DoModal() == IDOK  )
{
CString str = pFileSave->GetPathName();
if((fp1=fopen(str.GetBuffer(10),"w"))==NULL)
return;
str.ReleaseBuffer();
}