Editing HP-GL (section)

== Design ==
The language is formed from a series of two letter codes ([[mnemonic]]s), followed by optional parameters. For instance an [[Arc (geometry)|arc]] can be drawn on a page by sending the string:

<code>AA100,100,50;</code>

This means ''Arc Absolute'', and the parameters place the center of the arc at absolute [[Cartesian coordinate system|coordinates]] 100,100 on the page, with a starting angle of 50 [[Degree (angle)|degrees]] measured counter-clockwise. A fourth optional parameter (not used here) specifies how far the arc continues, and defaults to 5 degrees.

When first introduced, HP-GL contained the following commands:

{| class="wikitable"
! Command
! Meaning
|-----
! colspan=2 | Vector Group
|-----
| <code>PA</code> x,y{,x,y{...}<nowiki/>} || Plot absolute [i]
|-----
| <code>PR</code> x,y{,x,y{....}<nowiki/>} || Plot relative [i]
|-----
| <code>PD</code> || Pen down
|-----
| <code>PU</code> || Pen up
|-----
! colspan=2 | Character Group
|-----
| <code>CA</code> n || Designate alternate character set n [i]
|-----
| <code>CP</code> spaces, lines || Character plot [d]
|-----
| <code>CS</code> m || Designate standard set m [i]
|-----
| <code>DI</code> run, rise || Absolute direction [d]
|-----
| <code>DR</code> run, rise || Relative direction [d]
|-----
| <code>LB</code> c, ..., c || Label [[ASCII]] string [c]
|-----
| <code>SA</code> || Select alternate character set
|-----
| <code>SI</code> wide, high || Absolute character size [d]
|-----
| <code>SL</code> tan θ || Absolute character slant (from vertical) [d]
|-----
| <code>SR</code> wide, high || Relative character size [d]
|-----
| <code>SS</code> || Select standard character set
|-----
| <code>UC</code> x, y, pen{, ...} || User defined character [i]
|-----
! colspan=2 | Line Type Group
|-----
| <code>LT</code> t{,l} || Designate line type t and length l [d]
|-----
| <code>SM</code> c || Symbol mode [c]
|-----
| <code>SP</code> n || Select pen [i]
|-----
| <code>VA</code> || Adaptive velocity
|-----
| <code>VN</code> || Normal velocity
|-----
| <code>VS</code> v{,n} || Select velocity v for pen n [i]
|-----
! colspan=2 | Digitize Group
|-----
| <code>DC</code> || Digitize clear
|-----
| <code>DP</code> || Digitize point
|-----
| <code>OC</code> || Output current position and pen status
|-----
| <code>OD</code> || Output digitized point and pen status
|-----
! colspan=2 | Axes
|-----
| <code>TL</code> tp{,tn} || Tick length [d]
|-----
| <code>XT</code> || X axis tick
|-----
| <code>YT</code> || Y axis tick
|-----
! colspan=2 | Set-Up Group
|-----
| <code>IP</code> p1x,p1y,p2x,p2y || Input p1 and p2 [i]
|-----
| <code>IW</code> xlo,ylo,xhi,yhi || Input window [i]
|-----
| <code>OP</code> || Output p1 and p2 [i]
|-----
! colspan=2 | Configuration Status
|-----
| <code>AP</code> || Automatic pen pickup [i]
|-----
| <code>DF</code> || Set default values
|-----
| <code>IM</code> e{,s{,p}<nowiki/>} || Input e, s and p masks [i]
|-----
| <code>IN</code> || Initialize
|-----
| <code>OE</code> || Output error [i]
|-----
| <code>OS</code> || Output status [i]
|}

{|class = wikitable
|+ Commands added (when?)
| {{code|SI}} w,h || set character width and height
|}

Formats:
* [i]: integer formats between -32767 and 32768.  No decimal point.
* [d]: decimal format between +/- 127.9999.  Optional decimal point.
* [c]: ASCII character