An HPGL(Hewlett-Packard Graphics Language) file contains an instruction set for plotter control, developed by Hewlett-Packard. Hewlett-Packard plotters use this file to draw and print vector and raster content on the paper.
Files with PPSM extension represent Macro-enabled Slide Show file format created with Microsoft PowerPoint 2007 or higher. Another similar file format is PPTM which differs in opening with Microsoft PowerPoint in editable format instead of running as Slide Show. When run as slide show, the PPSM file shows the presentation slides with contents intact in the slide show and is in read-only mode by default. PPSM files can still be edited in Microsoft PowerPoint by opening it in PowerPoint.
You can also convert PLT into many other file formats. Please see the complete list below.