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<h1>Introduction</h1>

<p>
The MBS programming language is an integrated part of the Varkon
system. Its main purpose is to act as a generic product modeling language
but it can also be used for other things.
</p>

<p>
All real products have some kind of structure.
They usually consist of several different parts and it is therefore important
to model the parts individually. MBS uses the concept of a MODULE to generically
define each type of part that is used in a product. Here's an example...
</p>

<pre class="box">
  MODULE plate_with_hole(
    FLOAT width:=100            >"Horisontal size ?";
    FLOAT height:=50            >"Vertical size ?";
    FLOAT hole_diameter:=30     >"Size of hole ?";
    STRING material*10:="Steel" >"What material ?");

  BEGINMODULE
    lin_ang(#1,vec(0,0),0,width);
    lin_offs(#2,#1,-height);
    lin_free(#3,startp(#1),startp(#2));
    lin_free(#4,endp(#1),endp(#2));
    arc_1pos(#5,vec(width/2,height/2),hole_diameter/2);
  ENDMODULE
</pre>

<p>
This module defines a rectangular plate with a hole in
the center. It has a name (plate_with_hole), it has 4 parameters with default
values and prompt strings (width, height, hole_diameter, material) and
it has a body with statements that defines its geometty generically.
</p>

<p>
In order to use this module to create an actual instance (part)
of a plate_with_hole we must first compile the text based MBS file into
a binary MBO equivalent and then call the module from within the Varkon
system. This can be done interactively or by another module. In any case
we have to provide actual values for all parameters or at least accept
the defaults. Varkon then evaluates (executes) the module using actual
parameters and stores the result in the DB database. This is what it
looks like:
</p>

<img src="intro_1.jpg"></img>

<p>
Each time we call
the module Varkon will evaluate it again and store a new instance in DB.
The result in DB from evaluating a module is called a part.
Each part holds its name, its actual parameter values and the entities
created by the statements in the body of the module.
</p>

<p>
Suppose now that we want to model a product consisting
of many differently sized plates next to each other with
a small distance between them.
</p>

<pre class="box">
  MODULE many_plates(
    INT   n:=5 >"How many ?";
    FLOAT d:=2 >"At what distance ?");

    INT i; ! This is a local variable

  BEGINMODULE
    for i:=1 to n do
      csys_1p(#1,"Z-plane",vec(0,0,i*d),0,0:PEN=2);
      part(#2,plate_with_hole(10,10-i,2,"Copper"),refc(1,i));
    endfor;
  ENDMODULE
</pre>

<p>
The result of evaluating this module is a part named many_plates
consisting of a number of other parts named plate_with_hole. Each
plate_with_hole is differently sized and placed in a plane of increasing
Z. Here is what it looks like:
</p>

<img src="intro_2.jpg"></img>

<p>
A part may consist of any number of other parts as
well as basic geometric entities like lines or arcs. Parts may also consist
of parts that consist of parts and so on down to a depth of maximum 10
levels.
</p>

<p>
In the example above we have used lin_ang(), lin_offs(), lin_free(), arc_1pos()
and csys_1p() to create the geometry. MBS includes more than 60 different
procedures that create geometry. There is also more than 300 additional procedures
that can be used to do other things ! Learning MBS syntax is easy. Learning how
to use MBS procedures takes a little longer but they all are documented
in this manual and you only need a few of them to get started.
</p>

<h2>Good luck !</h2>


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