The .PTX file extension is used as a Court Reporter Transcript file or as RAW file generated from a Pentax camera
.pptx
The default file name is Presentation 1 The default file extension is .pptx
.pptx is for Pwerpoint 2007 and onwards, including Powerpoint 2013.
.pptx
I believe the default is .pptx (The old default used to be .ppt)
.ppt is the file extension for power point files
.ppt for versions up to 2003 and .pptx from version 2007 onwards.
The earlier extension in power point was PPT. The newer extension is PPTX in power point.
Typical Office 2007 documents use 4 letter extensions. These include .xlsx for Excel, .pptx for Powerpoint and .docx for Word. Access however, uses .accdb as an extension, so it has 5 letters.
The 2007 versions of Microsoft Office suite introduced an XML file format, which actually has more than one file, but then all of these files are compressed, using the ZIP format, into a single file. The file extension has an X at the end. So while previous versions of PowerPoint had a .PPT extension, the new format has .PPTX extension, to denote the new format.
In Microsoft Office 2007 and 2010, the extension is .pptx, whereas in earlier versions it was .ppt.
A file name is the main name given to a file, such as document.docx. The file extension, represented by the characters after the dot, indicates the type of file and helps the operating system identify which software to use to open the file. For example, in document.docx, ".docx" is the file extension indicating that it is a Microsoft Word document.