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ISOFTWARE REVIEW<br />
The ZX81 soft<br />
selection<br />
Nick Pearce casts his eye over some new<br />
releases.<br />
Tiny LOCO<br />
Computer Magic<br />
Tiny LOGO is an implementation<br />
for the ZX81 of the popular<br />
Massachusetts Institute of<br />
Technology programming<br />
language called LOGO, adaptations<br />
of which are now available<br />
for many personal computers.<br />
The principles of LOGO were<br />
described by Tim Hartnell back<br />
in the April May issue of ZX<br />
Computing and a LOGO translation<br />
program for the Spectrum,<br />
"Slogo",by David Nowotnik<br />
was presented in the following<br />
three issues. Briefly, LOGO was<br />
designed to provide an introduction<br />
to computer programming<br />
with particular emphasis on<br />
simplicity and the development<br />
of logical thinking. The most<br />
familiar aspect of LOGO is "turtie<br />
graphics", whereby a<br />
"turtle" on the screen moves<br />
according to the programmer's<br />
commands. As it travels, it<br />
leaves behind a trail, and in this<br />
way pictures can be created by<br />
telling the turtle where to go.<br />
The turtle in Tiny LOGO is a<br />
pixel. This caused me some difficulty,<br />
since there is no indication<br />
on screen of the direction<br />
the turtle is facing. The trail left<br />
by the turtle is also in pixels, so<br />
picture resolution is limited to<br />
the ZX81's 63 x 43 screen pixels.<br />
Another problem is that the<br />
program runs rather slowly,<br />
there is a pause during which the<br />
screen is blank in between executing<br />
each command, and I<br />
think the slowness would be<br />
frustrating were the program to<br />
be used for extended periods.<br />
The program is written entirely<br />
in BASIC, ideally a LOGO<br />
translation program should be<br />
written in machine code to give<br />
a faster operating speed.<br />
In other respects the program<br />
is very good with a comprehensive<br />
set of turtle graphics com<br />
mands as well as more advanced<br />
procedures (the language works<br />
by defining sequences of steps<br />
called procedures which are then<br />
called and executed). There is an<br />
editing facility so that pro-<br />
102<br />
cedures can be easily modified<br />
or corrected. These are kept in<br />
anarea called the"workspace",<br />
which can contain up to fifteen<br />
procedures. Procedures, as well<br />
as screen displays, can be saved<br />
on cassette.<br />
There is no shorthand in Tiny<br />
LOGO, all commands have to be<br />
typed in full, which can be<br />
somewhat timeconsuming. The<br />
cassette comes complete with a<br />
well-written instruction booklet<br />
which explains the language by<br />
means of short example pro<br />
grams and contains two useful<br />
appendices — a command summary<br />
table and an explanation of<br />
the program's error reports.<br />
LOGO has been described<br />
as the language of the '80s . It is<br />
beginning to be used in school<br />
classrooms, and whilst Tiny<br />
LOGO on the ZX81 has some<br />
shortcomings, it would nevertheless<br />
be a worthwhile investment<br />
for children with access to<br />
a 16K ZX81 just starting their<br />
computer education.<br />
Tiny LOGO by Computer Magic<br />
is published by International<br />
Publishing and Software Inc.<br />
3948 Chesswood Drive,<br />
Downview, Ontario, Canada.<br />
M3J2W6.<br />
Home Heating<br />
Calculations<br />
Harlequin<br />
Computing<br />
This program calculates the savings<br />
in heating costs for roof and<br />
cavity wall insulation, double<br />
glazing and draught-proofing. It<br />
is designed to enable the home<br />
owner to decide whether insulation<br />
is an economic proposition<br />
for his particular property, and<br />
the type of insulation he would<br />
do best to install. The program is<br />
easy to use. Once LOADed, the<br />
user is faced with a menu of five<br />
options. These enable the user<br />
to calculate: the total annual<br />
heating cost for a property; the<br />
average annual savings possible<br />
with roof or wall insulation, double<br />
glazing or draught-proofing;<br />
the cost of installing the insulation;<br />
payback period in years;<br />
and the percentage return on the<br />
investment. For each option, the<br />
user is prompted to enter roof,<br />
wall and window areas and<br />
"u"-values, and other pertinent<br />
information. Typical values are<br />
given for terraced, detached and<br />
semi-detached houses, but the<br />
user is recommended to use actual<br />
values from measurements<br />
where possible. When all the required<br />
data have been entered<br />
the answer for the selected option<br />
is calculated and displayed<br />
on screen. A simplified graph<br />
may also be drawn.<br />
The package includes a comprehensive<br />
instruction manual<br />
which contains a considerable<br />
amount of useful information on<br />
home insulation. I have just two<br />
criticisms. The same data has to<br />
be keyed in for different menu<br />
options, so it would make<br />
the program quicker to use if the<br />
data tables were transferable<br />
between options; and the program<br />
may not be readily usable<br />
with "unusual" properties (for<br />
example a house already part<br />
double glazed, or, as in my cottage,<br />
where the upper story is of<br />
different construction to the<br />
ground). Nevertheless, House<br />
Heating Calculations is an excellent<br />
package and would be a<br />
worthwhile investment for a<br />
home owner considering insulating<br />
his property.<br />
Harlequin Computing are at 18<br />
Hey wood Road, Great Sutton,<br />
South Wirral.<br />
EURO AIRWAYS and<br />
STOCKMARKET<br />
G. Barker<br />
Euro Airways and Stockmarket<br />
are both games of strategy for<br />
the 16KZX81.<br />
The aim of Euro Airways is to<br />
either earn f" 1 million or own 1 0<br />
aircraft within three years of<br />
becoming chairman of the company,<br />
and before going bust, being<br />
sacked, or forced to resign.<br />
You start with assets of<br />
£ 50,000, no aircraft but with a<br />
rented hanger at Heathrow and<br />
a new licence. Toturn£50,000<br />
into£l million in three years is a<br />
tall order. Indeed, it is difficult to<br />
make any profit at all, so high are<br />
the various operating costs of<br />
Euro Airways and considering<br />
the inevitable disasters that<br />
befall the airline each season.<br />
The game progresses<br />
through each season of the<br />
three years, and for each session<br />
goes through various phases.<br />
Firstly you must decide how<br />
many aircraft to charter (up to<br />
ten), and crew levels and pay.<br />
Low crew levels can lead to<br />
flight cancellations, and low pay<br />
to strikes, so careful thought is<br />
required in setting these<br />
parameters. You must then<br />
decide to which of 25 major<br />
cities your aircraft will fly. Certain<br />
information is provided to<br />
help in making a good choice,<br />
such as fuel costs for each flight,<br />
and the average ticket price on<br />
other airlines. The next step is to<br />
decide on ticket prices, and take<br />
out an insurance policy. From<br />
then on, you're in the hands of<br />
chance and the results of the<br />
business decisions you make.<br />
Hazards are numerous, I suffered<br />
two crashes in my first<br />
two seasons, and aircraft may<br />
be sabotaged, hijacked, flights<br />
ZX COMPUTING APRIL/MAY 1985
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