PLT file format
The PLT file format was developed for making positional images with Hewlett-Packard plotters, was used for the first time in the HP-8972 plotter of 1977. It is a part of the Hewlett-Packard Graphics Language (HPGL), designed as a printer control language. The average PLT file contains a series of two-letter data that determines the starting point of the plotter head. Quite a several graphics applications support the PLT format, and better still could have the image size adjusted without altering the source code, or image quality. The PLT is designed on a text file framework, similar to ASCII.
In recent years, PLT files are created by an innovative visualization software called Tecplot. Unlike the relatively medieval plotters, Tecplot analyses a series of dataset or multiple frames representing the software's input; the output of such computational analysis is documented in the PLT format. The PLT files often contain animated simulation results on complex 2D and 3D visualization, which is not realistic or economical to conduct in reality. The resulting PLT output could be either a static image or an animated visualization.