Known HP-GL commands

hp2xx emulates a subset of the Hewlett-Packard 7550A plotter. The following manual was used as reference for command definitions: [1] HP 7550A Interfacing and Programming Manual.

Not all commands are supported. Among the non-supported commands are those which do not really apply to a software emulator, like:

commands affecting the communication between plotter and host computer,
commands for changing the behaviour of a real plotter, like plotting speed etc.,
commands for the control of plotter memory allocation,
commands causing various plotter display outputs.

Other non-supported commands would be desirable, but were left out due to their inherent complexity (or just because nobody pushed me, :-) ). Among those are:

commands for font (character set) management. Since there is only one font
         built into hp2xx, there is no point in providing font switching etc.
windowing/clipping and rotation
polygon and box filling commands

Programmers intending to add more HP-GL features should take care to implement the less-than-obvious side effects of existing commands on the new features, too (and vice versa). E. g., line types (LT;) affect most but not all drawing commands: While the ER; command (edge rectangle relative) uses the current line type, its counterpart EA; (edge rectangle absolute) always draws solid lines. However, both PR; and PA; use the current line type! In addition, new features may need initializations by the already supported codes IN; or DF;, so these may have to be expanded. So carefully consult [1] prior to adding new HP-GL commands.

The remainder of this section lists all HP-GL commands given on pages 1-2 to 1-4 of [1] and marks them as either

      (.)  not applicable,
      (-)  ignored, or
      (+)  supported.

The label "supported" is used when I think the command is fully supported in the context of the already implemented commands. In general, you should have absolutely no problem with this class of commands.

Though there still are unsupported commands, this does not mean that you might have trouble using hp2xx. Nowadays, most HP-GL files are machine-generated, e.g. by CAD or DTP programs. These tend to make use of just a simple subset of HP-GL. To my experience, chances are high that hp2xx will give you the picture you want!

HP-GL|s n| Description & Remarks
Cmd  | i |
=====|===|========================================================
AA   |+  | Arc Absolute
AF   |+  | [same as PG]
AH   |+  | [same as PG]
AP   |  .| Automatic pen operations
AR   |+  | Arc Relative
AS   |  .| Acceleration select
-----|---|--------------------------------------------------------
BF   | - | Buffer Plot
BL   |+  | Buffer Label
-----|---|--------------------------------------------------------
CA   | - | Designate alternate character set
CC   | - | Character Chord angle
CI   |+  | Circle
CM   | - | Character selection mode
CP   |+  | Character plot
CS   | - | Designate standard character set
CT   | - | Chord tolerance
CV   | - | Curved line generator
-----|---|--------------------------------------------------------
DC   |  .| Digitize clear
DF   |+  | Default
DI   |+  | Absolute direction
DL   | - | Define downloadable character
DP   |  .| Digitize point
DR   |+  | Relative direction
DS   | - | Designate character into slot
DT   |+  | Define label terminator
-----|---|--------------------------------------------------------
EA   |+  | Edge rectangle absolute
EP   | - | Edge polygon
ER   | - | Edge rectangle relative
ES   |+  | Extra space
EW   | - | Edge wedge
-----|---|--------------------------------------------------------
FP   | - | Fill polygon
FS   |  .| Force select
FT   | - | Fill type
-----|---|--------------------------------------------------------
GC   |  .| Group count
GM   |  .| Graphics memory
-----|---|--------------------------------------------------------
IM   | - | Input mask
IN   |+  | Initialize
IP   |+  | Input P1 and P2
IV   | - | Invoke character slot
IW   | - | Input window
-----|---|--------------------------------------------------------
KY   |  .| Define key
-----|---|--------------------------------------------------------
LB   |+  | Label
LO   |+  | Label origin
LT   |+  | Line type
-----|---|--------------------------------------------------------
NR   |  .| Not ready (unload page)
-----|---|--------------------------------------------------------
OA   |  .| Output actual position and pen status
OC   |  .| Output commanded position and pen status
OD   |  .| Output digitized point and pen status
OE   | - | Output error
OF   | - | Output factors
OG   |  .| Output group count
OH   | - | Output hard-clip limits
OI   |  .| Output identification
OK   |  .| Output key
OL   | - | Output label length
OO   |  .| Output options
OP   |+  | Output P1 and P2
OS   | - | Output status
OT   |  .| Output carousel type
OW   | - | Output window
-----|---|--------------------------------------------------------
PA   |+  | Plot absolute
PB   |+  | Print buffered label
PD   |+  | Pen down
PG   |+  | Page feed
PR   |+  | Plot relative
PT   | - | Pen thickness
PU   |+  | Pen up
-----|---|--------------------------------------------------------
RA   | - | Fill rectangle absolute
RO   | - | Rotate coordinate system  [use option -r instead!]
RP   | - | Replot
RR   | - | Fill rectangle relative
-----|---|--------------------------------------------------------
SA   | - | Select alternate character set
SC   |+  | Scale
SI   |+  | Absolute character size
SL   |+  | Character slant
SM   |+  | Symbol mode
SP   |+  | Select pen
SR   |+  | Relative character size
SS   | - | Select standard character set
-----|---|--------------------------------------------------------
TL   |+  | Tick length
-----|---|--------------------------------------------------------
UC   |+  | User-defined character
UF   | - | User-defined fill type
-----|---|--------------------------------------------------------
VS   |  .| Velocity select
-----|---|--------------------------------------------------------
WD   |+  | Write to display
WG   | - | Fill wedge
-----|---|--------------------------------------------------------
XT   |+  | X-Tick
-----|---|--------------------------------------------------------
YT   |+  | Y-Tick