X PixMap (.xpm)
The XPM file format is a text-based graphical standard, crucial for icon storage in the X Window System. It supports transparency, facilitating versatile icon design. Editable via text editors and integrable into C/C++ code, it was developed by Dardailler and Nahaboo at the Bull Research Center and later enhanced by Le Hors, making it indispensable for GUI development.