Display Procedures
Although the use of structured display files
is widespread in interactive computer graphics, 
these structures present a number of problems which
tend to restrict their generality and usefulness. 
 This paper discusses some of these problems, and suggests an
alternative approach to display system 
design which avoids the use of structured display files.
 This technique employs display procedures to 
generate information for display.  By including transformations
within calls to these procedures it is 
possible both to simplify the specification of pictures
and to speed up their generation.  Display procedures 
permit picture elements to be defined conditionally
and also facilitate the processing of inputs from 
pointing devices.  The paper is illustrated by examples
from aversion of the EULER language in which 
display procedures were implemented.
CACM October, 1971
Newman, W. M.
