HP/GL File Utilities for IRIX

Here is a growing collection of HP/GL file utilities and viewers for use on SGI-IRIX workstations.

What is HP/GL and how is it different than HP/GL-2?

HP/GL was developed by Hewlett Packard to drive its family of pen plotters. Most commands are vector oriented - pick up the pen, put down the pen, move here, move there. Very few complex commands are part of HP/GL since the original plotters did not include powerful CPUs.

HP/GL-2 was developed as a successor to HP/GL to support many more advanced features that could be offloaded to plotters with powerful CPU's and large amounts of memory. HP/GL-2 also includes quite a lot of raster controls and commands since most modern plotters are actually raster devices. This includes embedded pen definitions (up to 256 since a raster device can never run out of pens...) fill patterns, screened vectors, clipping windows, data transformation and the like.

Most plotter drivers do not take advantage of the advanced HP/GL-2 functions since they are based on old code that originally supported basic HP/GL. However one very popular HP/GL-2 command that is often used is PE (PoylineEencoded command). PE is very popular because it compresses the pen movement commands by encoding them. This significantly reduces the plot file size. However PE is more difficult to decode which is why many HP/GL to DXF programs don't properly support it.

Command HP/GL HP/GL-2 Description
SP x x
Selects a pen; data mapped to AutoCAD layer:
  Layer#=10xpen number + line-type
PA x x move Pen Absolute
PR x x move Pen Relative
PE x
Polyline Encoded - a series of movements encoded
to minimize bytes used.
PU x x Pen Up
PD x x Pen Down
PW x
Pen Width - translated to polyline with width
IP x x new user unit scale factor
AA x x Arc Absolute
AR x x Arc Relative
EA x x
outline of rectangle translated to a zero width closed polyline
LB x x string of text - to DXF text
DT x x string termination character
SI x x character height
DI x x direction (angle) of text
CS x x text scaling parameter
CI x x CIrcle
SC x x SCale factor
LT x x
Line Type - indirectly supported by mapping to a unique
AutoCAD layer

Some HP/GL and HP/GL-2 Commands

Last updated: 07.OCT.1997