data sources and requirements, available 
functions and some hints or intermediate 
steps. The student then has to build up a 
procedure as a processing flow, that is the 
order in which the image processing and GIS 
functions are to be applied. Guidance for this 
should be provided by a problem-solving and 
model-driven approach. 
The WIMP provides an easy way to prevent 
students from peeking into programs which 
are not required for the exercise at hand. Only 
menu items needed for the exercise are 
selectable. Educational software has certain 
requirements with respect to student expecta 
tions and limitations. The system is thus 
designed according to the following specifica 
tions: 
Menu-driven 
The package is intended to be used by 
students with little or no experience with 
computers. Emphasis is thus placed on a 
user-friendly interface between man and ma 
chine. Menu selections require only a mouse 
or a few keystrokes. Students are not to be 
burdened with difficult commands which they 
have to memorize. They should be able to 
learn how to use the system within 10 minutes 
and without having to resort to a user manual 
while working with it The menu structure is 
hierarchical and the logic behind it consistent, 
such that all functions are found where they 
are to be expected. 
On-line help 
An on-line help function can be accessed for 
every function within the system. It will give 
detailed and relevant information for the 
specific function. The user can continue his 
activities without having to leave the HELP 
function. This is possible because of the 
multi-tasking provided by the Archimedes 
RISC-OS operating system. 
Friendly and helpful error messages 
Error messages are polite, don’t blame the 
user and eventually suggest solutions. 
5. Conclusions 
Image processing and GIS are more and 
more implemented on small workstations or 
PC-type computers. The Archimedes, with its 
RISC processor and colour capabilities, pro 
vides a very suitable environment to do 
image processing. Speed and display com 
pare favourably with much more expensive 
systems. Moreover, the operating system with 
its window environment makes it particularly 
suited for students with little or no experience 
with computers. Since almost any command 
of the operating system can be executed 
within the window environment, there are no 
difficult commands and syntax to learn, but 
the use is more intuitive. No special hardware 
is required to run Alexander, though upgra 
ding to 4 Mbyte and a multisync monitor 
makes the system a professional package. 
The data format of Alexander allows easy 
integration with standard pixel editing and 
drawing packages of the Archimedes. Thus 
any result achieved with image processing 
can be further edited, e.g. to produce an 
annotated map of a classified area. This 
could again be part of a desktop publishing 
package (DTP) for high quality output of 
reports. 
Version 1.0 of the Alexander package pro 
vides for the most commonly used image 
processing functions. Extensions, such as 
mml transformation, are scheduled for a first 
update. Attention will also focus on GIS 
functions for future work. The system is 
intended to be easy to learn. It should be 
possible to learn its operation within 10 
minutes. However, this has not been tested 
yet thoroughly.