Editing Plotter (section)

==Languages==
A number of [[printer control language]]s were created to operate pen plotters, and transmit commands like "lift pen from paper", "place pen on paper", or "draw a line from here to here". Three common [[ASCII]]-based plotter control languages are [[Hewlett-Packard]]'s [[HP-GL]], its successor HP-GL/2, and [[Houston Instruments]] [[DMPL]]. Here is a simple HP-GL script drawing a line:
<pre>
SP1;
PA500,500;
PD;
PR0,1000;
PU;
SP;
</pre>

This program instructs the plotter, in order, to take the first pen (SP1 = Select Pen 1), to go to coordinates X=500, Y=500 on the paper sheet (PA = Plot Absolute), to lower the pen against the paper (PD = Pen Down), to move 1000 units in the Y direction (thus drawing a vertical line - PR = Plot Relative), to lift the pen (PU = Pen Up) and finally to put it back in its stall.

Programmers using [[Fortran|FORTRAN]] or [[BASIC]] generally did not program these directly, but used software packages, such as the Calcomp library, or [[device independent]] graphics packages, such as Hewlett-Packard's [[A Graphics Language|AGL]] libraries or BASIC extensions or high end packages such as [[DISSPLA]]. These would establish scaling factors from world coordinates to device coordinates, and translate to the low level device commands. For example, to plot X*X in [[HP 9830]] BASIC, the program would be
<syntaxhighlight lang=BASIC>
10 SCALE -1,1,1,1
20 FOR X = -1 to 1 STEP 0.1
30 PLOT X, X*X
40 NEXT X
50 PEN
60 END
</syntaxhighlight>
[[File:Video of plotter marking on the samples.ogv|thumb|Label plotter]]