C / C++ / MFC

//for ppt files

ifstream in_fp;
	DISPPARAMS dpNoArgs = {NULL, NULL, 0, 0};
	VARIANT vResult;	// used to hold variant results
	OLECHAR FAR* szFunction;
	IDispatch* pDispApp;
	IDispatch* pDispXlBooks;
	DISPID dispid_Books; 	//Documents property of application object
	DISPID dispid_Quit;
	BSTR bstrFileName = ::SysAllocString(OLESTR("filename"));
	BSTR bstrPassWord = ::SysAllocString(OLESTR("pass"));
 
	CString error_str=_T("");
	in_fp.open(file_name, ios::in);
	if (!in_fp || file_name.GetLength() > MAX_PATH)
	{
		error_str.Format(_T("error loading %s\n"), file_name);
		AfxMessageBox(error_str);
		return ;
	}
 
	string ss = string(CT2CA(file_name));
 
	const char *szFileName = ss.c_str();
 
	wchar_t wszFileName[MAX_PATH+1];
 
	//convert file name to bstr for use with COM
	MultiByteToWideChar(CP_ACP, 0, szFileName, strlen(szFileName)+1,
			wszFileName, sizeof(wszFileName)/sizeof(wszFileName[0]));
 
	bstrFileName = ::SysAllocString(wszFileName);
	
	// COM work starts here

	//Initialize COM
	::CoInitialize(NULL);
 
 
	//get the CLSID for the Excel Application Object
	CLSID clsid;
 
//for word files 
//use "Word.Application"

//and for excel files
//use "Excel.Application"

	CLSIDFromProgID(L"Powerpoint.Application", &clsid);
 
	//get a pointer to the Objects IUnknown interface and Create
	//an instance of the Excel Application.

	IUnknown* pUnk;
	HRESULT hr = ::CoCreateInstance( clsid, NULL,
			CLSCTX_SERVER, IID_IUnknown, (void**) &pUnk);
 
	
 
	hr = pUnk->QueryInterface(IID_IDispatch, (void**)&pDispApp);
 
	
//for word files 
//use "Documents"

//and for excel files
//use "Workbooks"

	szFunction = OLESTR("Presentations");
	hr = pDispApp->GetIDsOfNames (IID_NULL, &szFunction, 1,
			LOCALE_USER_DEFAULT, &dispid_Books);
 
	hr = pDispApp->Invoke (dispid_Books, IID_NULL,
			LOCALE_USER_DEFAULT, DISPATCH_PROPERTYGET,
			&dpNoArgs, &vResult, NULL, NULL);
 
	pDispXlBooks = vResult.pdispVal;
 
	//DISPPARAMS for Open method

	DISPID dispid_Open;
	VARIANT vArgsOpen[5];
	DISPPARAMS dpOpen;
	dpOpen.cArgs = 5;
	dpOpen.cNamedArgs = 0;
	dpOpen.rgvarg = vArgsOpen;
	
	wchar_t wszPassWord[MAX_PATH];
 
	
	ss = string(CT2CA(Password));
 
	const char *pwd_entry = ss.c_str();
 
	//again convert to bstr
	MultiByteToWideChar(CP_ACP, 0, pwd_entry, -1,
			wszPassWord, sizeof(wszPassWord)/sizeof(wszPassWord[0]));
 
	bstrPassWord = ::SysAllocString(wszPassWord);
		
	vArgsOpen[4].vt = VT_BSTR;
	vArgsOpen[4].bstrVal = bstrFileName;		//Filename
	vArgsOpen[3].vt = VT_ERROR;
	vArgsOpen[3].scode = DISP_E_PARAMNOTFOUND;	//Updatelinks - ommitted
	vArgsOpen[2].vt = VT_BOOL;
	vArgsOpen[2].scode = TRUE;					//Open ReadOnly
	vArgsOpen[1].vt = VT_ERROR;
	vArgsOpen[1].scode = DISP_E_PARAMNOTFOUND;  //file format - ommitted
	vArgsOpen[0].vt = VT_BSTR;
	vArgsOpen[0].bstrVal = bstrPassWord;		//the file password;

	//Invoke the Open method
	szFunction = OLESTR("Open");
	hr = pDispXlBooks->GetIDsOfNames(IID_NULL, &szFunction, 1, 
			                            LOCALE_USER_DEFAULT, &dispid_Open);
	hr = pDispXlBooks->Invoke(dispid_Open, IID_NULL, 
			                    LOCALE_USER_DEFAULT, DISPATCH_METHOD, 
								&dpOpen, NULL, NULL, NULL);
	
 
	if (!FAILED(hr)) 
	{
		//file open ok
	}
	else
	{
//its return error "invalid number of parameters"
		//file not open
	}
	
	//Invoke the Quit method

    szFunction = OLESTR("Quit");
    hr = pDispApp->GetIDsOfNames(IID_NULL, &szFunction, 1, 
                                 LOCALE_USER_DEFAULT, &dispid_Quit);
    hr = pDispApp->Invoke (dispid_Quit, IID_NULL, 
                           LOCALE_USER_DEFAULT, DISPATCH_METHOD,
                           &dpNoArgs, NULL, NULL, NULL);
 
	//Clean-up

	::SysFreeString(bstrFileName);
	::SysFreeString(bstrPassWord);
 
	pDispXlBooks->Release();
	pDispApp->Release();
	pUnk->Release();
 
	::CoUninitialize();