.GROB File Extension
File TypeGraphic Object Bitmap File
What is a GROB file?
Bitmap image called a "GROB" (GRaphic Object Bitmap); created with a Hewlett-Packard scientific graphing calculator, such as the HP-48 and HP-49; may contain a graph, chart, or other graphic created on the calculator.
GROB files typically have a .GRO extension.