$18(Example IV: Structured program display)
$p1
Another example is that of a structured display of programs, where the
language syntax tree has been mapped almost directly onto the
display graph.
$b1
#
$p1
Appropriate "recipe" subgraphs have been initially created to describe
the mode of printing basic strings. The keyword printing environment
has been defined as "times roman bold" in white, names 
have been declared as strings in red "times roman", comments as italicised
green strings and all the remaining syntactic tokens are printed in blue.
Each token has been declared once with its multiple appearances
implemented through pointers. 
$p1
The layout of the program on the screen is obtained through appropriate
pairing of syntactic constructs of the language with their
graphics structure definitions.
A block is a vertical composition of a $22[Begin] token with
an indented, vertically composed list of statements and an $22[End]
token at the bottom. Indentation is achieved through a $22[Move](indentstep,0)
node above the statements list. Such a construct when nested, allows
for nested indentation of program representation on the screen.
$p1
Having declared the cursor as a framing box it is possible now to
frame addressed syntactic nodes of the program through placing
$22[Cursor] flags on the corresponding nodes of its graphics representation.
Here the cursor is placed on the block under the $22[While] loop.
$n
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