APT Language Structure

The APT language was originally developed in the line of the FORTRAN computer language which was the most common language used by scientists in early 1950s. It consists of series of statements that utilize a syntax similar to FORTRAN language using a number of keywords formed similar to their English equivalents. For example, the vocabulary word CIRCLE means a definition for a circle geometry. Some of the vocabulary words that we will be using in this course for developing the programs are given below with a simple explanation. They will be further expanded later.

Geometry

ARC           :              Circular pattern for multiple point definition

ATANGL      :           At an angle of measured from positive X-axis direction

CANON       :           Canonical information for geometry

CCLW        :           Counter clockwise direction

CENTER      :           Center of a circle

CIRCLE      :           Geometry definition of a circle

CLW          :            Clockwise direction

DECR         :            Decrementing the numbering

ELLIPS       :           Ellipse geometry definition

GCONIC     :           General conic geometry definition

HYPERB      :           Hyperbola geometry definition

IN              :           Inside as a modifier used with geometry definition

INCR          :           Incrementing the numbering

 INTOF       :           Intersection of two curves

LARGE        :          A circle with larger radius

LEFT          :           Geometry to be seen towards the left as a geometry modifier

LINE          :           Geometry definition of a Line

LINEAR      :           Linear pattern for multiple point definition

MATRIX     :           Geometry definition of a matrix transformation of geometry

MIRROR    :           Geometric transformation modifier

OUT          :           Outside as a modifier used with geometry definition

PARLEL      :           Parallel to as a modifier used with geometry definition

PATERN     :           Geometry definition of a pattern for multiple points

PLANE       :           Geometry definition of a plane surface

POINT       :           Geometry definition of a point used for drilling operations

RADIUS     :           Radius of a given circle

RANDOM     :           Random pattern for multiple point definition without any known symmetry

RIGHT        :           Geometry to be seen towards the right as a geometry modifier

RTHETA      :             For polar coordinates with radius first followed by angle

SMALL        :           A circle with smaller radius

TANTO        :           Tangent to

THETAR      :          For polar coordinates with angle first followed by radius

THRU         :           Through as a modifier used in pattern definitions to specify the point numbers.

TRANSL       :           Geometric transformation modifier for translation

VECTOR       :           Geometry definition of a vector

XAXIS          :           X-axis to be used as a line

XCOORD      :           X-coordinate value

XLARGE       :           The point with larger X-coordinate value

XSMALL       :           The point with smaller X-coordinate value

XYPLAN       :           XY plane used with polar coordinates

XYROT        :           Rotation about the Z-axis (in X-Y plane)

YAXIS         :           Y-axis to be used as a line

YCOORD     :           Y-coordinate value

YLARGE       :           The point with larger Y-coordinate value

YSMALL       :           The point with smaller Y-coordinate value

YZPLAN       :           YZ plane used with polar coordinates

ZSURF        :           Z surface as a plane having the same Z-coordinate value for all points

ZXPLAN       :           ZX plane used with polar coordinates

Some of the above are termed as Major words that actually describe a class of geometry definition. Examples are Point, Line, Circle, Matrix, etc. The others are called as minor words that could be used to classify a major word to come to the exact definition. These are normally used to classify the data being supplied for a given geometry definition. For example, to define a line as parallel to another line already defined as follows:

LIN3 = LINE / PNT1, PARLEL, LIN2

LIN3 is a new line that is passing through an already defined point PNT1 and parallel to another already defined line LIN2.

The syntax of statements as used can be noticed from the above statement. The geometric elements can be given with identification symbols, which can be formed by the programmer up to a maximum of six characters. They can be formed using English alphabets and numerals with the starting always an alphabet. They should not be same as the vocabulary words.

A slash is used to divide a statement into two sections. To the left of the slash are the MAJOR words, and to the right are the words, symbols and/or scalars that modify the word on the left of the slash so as to give it a complete and precise meaning or definition, e.g. CIRCLE / CENTER, PNT3, RADIUS, 20. A comma is used as a separator between the elements in a statement generally to the right of the slash. An equals sign is used for assigning an entity to a symbolic name.

In addition to the geometry statements an APT program consists of motion, postprocessor and compilation control statements.