Specifications

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and provides the equivalent of the IBM
colour/graphics adapter on the main
board, the scope for expansion compares
favourably with the IBM PC. With or
without the expansion unit the
Challenger's memory can be expanded to
256K internally. Maximum memory size
is 640K, although increasing memory to
this size would require the addition of a
separate memory board inside the B unit.
The double-sided disk drives provide
twice the storage capacity of those of the
IBM PC and are able to read and write
disks formatted for use with MS-DOS
1.0, MS-DOS 2.0 and PC-DOS.
Adding the expansion unit to the
Challenger requires some assembly work.
The B unit is the same width and depth
as the system unit but is 14cm high and
designed to sit on top of the A module,
connected to it by two edge connectors
and a 240V power cord. Putting the two
together requires finding and making
these connections and then removing
three plastic cut-outs from each side of
the system unit to allow the two to be
locked together. In its expanded form the
Challenger is big and imposing, and at
24cm high, is too tall to support a video
monitor at a comfortable viewing angle.
Internally, the Challenger is built with
the precision of military equipment.
There is a remarkable amount of unused
space inside both A and B units, and the
design could perhaps be improved by
reducing the height of the two units. The
keyboard storage space inside the system
unit in particular seems an unnecessary
refinement. On the plus side, the open
design combined with a fan in the system
unit means that there should be no
problem with heat build-up.
When first switched on the Challenger
performs a self-diagnostic program and
then checks an internal switch to
determine whether an expansion unit
and disk drives are available. Depending
on the setting of this switch the
computer then either boots from a
system disk or activates ROM BASIC.
The video display
Screen displays of graphics and text on
the Challenger are identical to those of
the IBM PC. Text can be displayed in
either 40 column by 25 lines or 80 x 25
line formats in one of 16 colours with
text, screen background and border
colours selected with the COLOR
statement. The colour codes are the same
as those of the IBM PC. In the 80
column mode four video "pages" are
available which can be written to and
displayed independently of each other,
while the 40 column mode allows eight
screens to be stored.
Graphics are available in two formats,
with either 320 x 200 or 640 x 200 screen
resolution, selected by the SCREEN
statement. The lower resolution graphics
mode allows the use of four colours
simultaneously, chosen from one of two
"palettes" which include the current
background colour. Any one of the 16
available colours can be used for the
background display. The 640 x 200
graphics mode allows higher resolution
displays but in black and white only.
Colour is not available.
Although text and graphics cannot be
mixed on the same screen, diagrams and
charts can be labelled by defining your
own text characters with graphics
commands. Graphics are supported by
the PSET, PRESET, LINE, CIRCLE,
PAINT, and DRAW statements of
Microsoft's Basic A while a limited form
of animation is possible with the GET
and PUT statements. GET stores a
specified area of the screen image in an
ELECTRONICS Australia, October, 1984  105