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.
TIFF or TIF, Tagged Image File Format, represents raster images that are meant for usage on a variety of devices that comply with this file format standard. It is capable of describing bilevel, grayscale, palette-color and full-color image data in several color spaces. It supports lossy as well as lossless compression schemes to choose between space and time for applications using the format.
You can also convert PLT into many other file formats. Please see the complete list below.