Convert TXT to PPT using C# or online

Aspose.Words.Document txt = new Aspose.Words.Document("sourceWordFile.txt");

// Save TXT file to HTML 
txt.Save("filepath\\test.html", SaveFormat.Html);

// To convert multi pages TXT documents, export each page to HTML separately using Aspose.Words and then use the below code to convert to PPT.

using (Presentation ppt = new Presentation()){

	// Access the default first slide of presentation
	ISlide slide = pres.Slides[0];

	// Adding the AutoShape to accomodate the HTML content 
	// Adjust it as of your need
	IAutoShape ashape = slide.Shapes.AddAutoShape(ShapeType.Rectangle, 10, 10, pres.SlideSize.Size.Width - 20, pres.SlideSize.Size.Height - 10);

	ashape.FillFormat.FillType = FillType.NoFill;

	// Adding text frame to the shape
	ashape.AddTextFrame("");

	// Clearing all paragraphs in added text frame
	ashape.TextFrame.Paragraphs.Clear();

	// Loading the HTML file using stream reader
	TextReader tr = new StreamReader("filepath\\test.html");

	// Adding text from HTML stream reader in text frame
	ashape.TextFrame.Paragraphs.AddFromHtml(tr.ReadToEnd());

	// Save the PPT Presentation
	ppt.Save("filepath\\pres.ppt", Aspose.Slides.Export.SaveFormat.Ppt);
}