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 ODP extension represents the presentation file format used by OpenOffice.org in the OASIS OpenDocument standard. A presentation file is a collection of slides where each slide can comprise text, images, formatting, animations, and other media. These slides are presented to an audience in the form of slideshows with custom presentation settings.
You can also convert PLT into many other file formats. Please see the complete list below.