Iiwge na«e ? 
ScQfce 
Landsat TM 
fr№S№: 
43 41 41 42 42 42 48 38 37 37 37 
45 42 41 42 43 42 38 37 37 37 36 
44 42 43 44 43 42 33 36 37 37 38 
Iteitnt ?<ra 
Figure 2: The window environment of Alexander. 
variety of properties, which are defined by the 
programmer. The most notable properties are: 
writable, menu icon, radio-button, dragable, 
exclusive selection group (figure 4). 
A writable icon can be used if the user has to 
input some textual information. One useful 
property of a writable icon is that the system 
developer can mask out certain characters, 
e.g. all letters, if the input must be a number. 
A menu icon will be highlighted automatically 
if the user moves the pointer over rt Two 
frequently used complementary menu icons 
are ‘Cancel’ and ‘O.K.’. After the user has 
made some selections within a dialogue box, 
depending on which menu icon is clicked on, 
the changes will then be brought into effect 
(or not). A radio-button is most useful in 
combination with several icons of this type 
which all belong to the same exclusive 
selection group. The function is basically that 
of an old radio: selecting one item will 
deselect others. A dragable icon can be 
dragged from its position to another part on 
the screen. This usually occurs when saving 
data or files in a directory. 
The standard machine comes with graphics 
capabilities to display 256 of 4096 colours. By 
changing the hardware palette, it is possible 
to define the colour ranges needed for the 
application. There are more than 20 different 
screen modes to choose from, their difference 
being the combination of spatial resolution 
and maximum number of colours. System 
software ensures that after a change of 
screen mode the spatial resolution and selec 
ted colours are matched as closely as pos 
sible-* 
The Archimedes can be connected via Econet 
to a network of workstations. Each work 
station has access to the shared hard disk