[FoodGood]

Hello everyone
I didn't understand something about office development..

I have this code from Microsoft site:

            using System;
            using System.Collections.Generic;
            using System.ComponentModel;
            using System.Data;
            using System.Drawing;
            using System.Linq;
            using System.Text;
            using System.Windows.Forms;
            using Microsoft.Office.Core;
            using PowerPoint = Microsoft.Office.Interop.PowerPoint;
            using Graph = Microsoft.Office.Interop.Graph;
            using System.Runtime.InteropServices;

private void ShowPresentation()
{
            PowerPoint.Application objApp;
            PowerPoint.Presentations objPresSet;
            PowerPoint._Presentation objPres;
            PowerPoint.Slides objSlides;
            PowerPoint._Slide objSlide;
            PowerPoint.TextRange objTextRng;
            PowerPoint.Shapes objShapes;
            PowerPoint.Shape objShape;
            PowerPoint.SlideShowWindows objSSWs;
            PowerPoint.SlideShowTransition objSST;
            PowerPoint.SlideShowSettings objSSS;
            PowerPoint.SlideRange objSldRng;
            Graph.Chart objChart;

            //Create a new presentation based on a template.
            objApp = new PowerPoint.Application();
            objApp.Visible = MsoTriState.msoTrue;
            objPresSet = objApp.Presentations;
            objPres = objPresSet.Add(MsoTriState.msoTrue);
                //objPresSet.Open(strTemplate,MsoTriState.msoFalse, MsoTriState.msoTrue, MsoTriState.msoTrue);
            objSlides = objPres.Slides;

            //Build Slide #1:
            //Add text to the slide, change the font and insert/position a 
            //picture on the first slide.
            objSlide = objSlides.Add(1, PowerPoint.PpSlideLayout.ppLayoutTitleOnly);
            objTextRng = objSlide.Shapes[1].TextFrame.TextRange;
            objTextRng.Text = "My Sample Presentation";
            objTextRng.Font.Name = "Comic Sans MS";
            objTextRng.Font.Size = 48;
            objSlide.Shapes.AddPicture(strPic, MsoTriState.msoFalse, MsoTriState.msoTrue,
                0, 0, objSlide.Master.Width, objSlide.Master.Height);

            //Build Slide #2:
            //Add text to the slide title, format the text. Also add a chart to the
            //slide and change the chart type to a 3D pie chart.
            objSlide = objSlides.Add(2, PowerPoint.PpSlideLayout.ppLayoutTitleOnly);
            objTextRng = objSlide.Shapes[1].TextFrame.TextRange;
            objTextRng.Text = "My Chart";
            objTextRng.Font.Name = "Comic Sans MS";
            objTextRng.Font.Size = 48;
            objChart = (Graph.Chart)objSlide.Shapes.AddOLEObject(150, 150, 480, 320,
                "MSGraph.Chart.8", "", MsoTriState.msoFalse, "", 0, "",
                MsoTriState.msoFalse).OLEFormat.Object;
            objChart.ChartType = Graph.XlChartType.xl3DPie;
            objChart.Legend.Position = Graph.XlLegendPosition.xlLegendPositionBottom;
            objChart.HasTitle = true;
            objChart.ChartTitle.Text = "Here it is...";

            //Build Slide #3:
            //Change the background color of this slide only. Add a text effect to the slide
            //and apply various color schemes and shadows to the text effect.
            objSlide = objSlides.Add(3, PowerPoint.PpSlideLayout.ppLayoutBlank);
            objSlide.FollowMasterBackground = MsoTriState.msoFalse;
            objShapes = objSlide.Shapes;
            objShape = objShapes.AddTextEffect(MsoPresetTextEffect.msoTextEffect27,
              "The End", "Impact", 96, MsoTriState.msoFalse, MsoTriState.msoFalse, 230, 200);

            //Modify the slide show transition settings for all 3 slides in
            //the presentation.
            int[] SlideIdx = new int[]{1};
            
            //for (int i = 0; i < 3; i++) SlideIdx[i] = i + 1;
            objSldRng = objSlides.Range(SlideIdx);
            objSST = objSldRng.SlideShowTransition;
            objSST.AdvanceOnTime = MsoTriState.msoTrue;
            objSST.AdvanceTime = 3;
            objSST.EntryEffect = PowerPoint.PpEntryEffect.ppEffectBoxOut;

            SlideIdx = new int[] { 2,3 };
            objSldRng = objSlides.Range(SlideIdx);
            objSST = objSldRng.SlideShowTransition;
            objSST.AdvanceOnTime = MsoTriState.msoTrue;
            objSST.AdvanceTime = 3;
            objSST.EntryEffect = PowerPoint.PpEntryEffect.ppEffectBlindsVertical;

            //Prevent Office Assistant from displaying alert messages:
            /*bAssistantOn = objApp.Assistant.On;
            objApp.Assistant.On = false;*/

            //Run the Slide show from slides 1 thru 3.
            /*objSSS = objPres.SlideShowSettings;
            objSSS.StartingSlide = 1;
            objSSS.EndingSlide = 3;
            objSSS.Run();*/

            //Wait for the slide show to end.
            //objSSWs = objApp.SlideShowWindows;
            //while (objSSWs.Count >= 1) System.Threading.Thread.Sleep(100);

            //Reenable Office Assisant, if it was on:
            /*if (bAssistantOn)
            {
                objApp.Assistant.On = true;
                objApp.Assistant.Visible = false;
            }*/

            //Close the presentation without saving changes and quit PowerPoint.
            objPres.SaveAs("Test Presentation", PowerPoint.PpSaveAsFileType.ppSaveAsPresentation, MsoTriState.msoFalse);
            objPres.Close();
            objApp.Quit();
}

This code creates ppt (2003-2007) file with some slides, and the library is "Microsoft PowerPoint 14.0 Object Library"
What's the different between version 14 to 9/12 etc...?
If I want my application to be compatible with office XP files & 2003-2007 files & 2010 files..How can I do it?..Should I add references to the older versions of the PowerPoint library?
and last question..How can I save the file as pptx file?

Thanks : )