also easy to use, modify and add to from the customer's point 
of view. 
2.2 Development Environment 
Ideally, a machine independent environment, such as ADA, should 
have been chosen, or at least a machine independent operating 
system e.g. UNIX. However, at the time of decision at the end 
of the last decade, these systems were not available, and so 
the choice of programming language and, to a lesser extent, 
operating system were critical. 
PASCAL was chosen as our programming language as it encourages 
standards, transparency and documentation of programs. Also, it 
is a language which allows ease of transportation to other 
systems in order to preserve the knowledge and time invested in 
the program development. 
Kern photogrammetric instruments use DEC and IBM AT compatible 
equipment for computer support. Previously, computers from the 
PDP and Micro 11 family were used with RT-11 single user 
operating system and TSX multi-user operating system. 
Nowdays, in addition to the PDP line, Kern photogrammetric 
equipment is available with DEC MicroVAX computer running under 
VAX/VMS operating system and also IBM AT compatible PC running 
under MS-DOS. 
2.3 Concept Implementation 
The concepts were implemented by using various software 
techniques. 
Software Standards 
- programming standards were specified thus software is 
easily augmented and maintained 
- subroutine generators were written which produce code 
according to input parameters. 
- operational and command standards were introduced for 
software use thus new programs are quickly mastered by 
the operator. 
Modularity 
- modular software eases development and maintenance. 
- users may combine selected portions of Kern software 
with user developed programs. 
Interactive Operation 
- easy input of program parameters. 
- effective examination and processing of results. 
- automatic driving of the DSR instrument when possible. 
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