spectrum utility - OpenLibra

Alphabetical order
Dear David,
I have programmed a list of articles
in random order, and can
interchange to get the lowest in
alphabetical order to be first in
the list. But I cannot work out
how to get the whole list into
alphabetical order. Please can
you help.
Mrs HG Blackwood,
Fife, Scotland
Dear Mrs Blackwood,
The listing you send me requires
little change to complete the
sort; using your line numbers,
variables and basic routine, here
is the complete sort routine:
190 FOR i = 2 TO n-1
200 FOR k = iTO n
210 IF n$(i-1 J n$|k) THEN
GOTO 250
220 LET t$ = n$(k)
230 LET n$(k) = n$(i-1)
240 LET n$(i-1) = t$
250 NEXT k
260 NEXT i
CLEARing
Dear David,
Although I have a 48K Spectrum,
I sometimes find that a
long program will not load after
NEWing a previous program.
Pulling out the power lead and
replacing it is the only way of
resetting the machine that I'm
aware of. ts there a simpler
way?
Ctive Williams,
Staines
Dear dive.
You can reset the Spectrum by
using the direct command:
RANDOMISE USR 0; this effects
the same ROM routine as
used by the computer when it is
first powered-up. The same
(SINCLAIR SOLUTION!
David Nowotnik answers your questions
command (RAND USR 0) will
also 'warm start' the ZX81.
Decimal places
Dear David,
I have recently bought a 48K
Spectrum, and wish to employ it
to help me with my Open University
Maths Foundation course.
Can I make the Spectrum work
to a fixed decimal place, and
preferably a corrected decimal
place?
Barry Murfett,
Hyde, Cheshire
Dear Barry,
The answer is 'yes', but it isn't
that simple. The Spectrum
doesn't have a print formatting
command (PRINT USING/
available on some other micros,
so you have to write a short
subroutine to do this. The listing
is too long for the Problem Page,
so /put it in the post to you. For
other readers who want to solve
this problem, the strategy for it
is as follows:
• Divide the number into its integer
and fractional parts with
the INT command,
• Multiply the fractional part by
10 to the power of n, where n is
the number of decimal places,
add. 5 (to round it), and take the
integer.
• Place both halves of the
number into strings (S TR$), pad
out with zeros, as necessary,
then combine the two strings
with a decimal point between
them. Then print the string, or
use VAL if you want to work on
the number some more.
Draughts
Dear David,
I am looking for a draughts program
for my 48K Spectrum. I
have looked through several
magazines, but I cannot find any
useful program. Do you know of
a firm who has such a program?
Fer Soorsma,
Brunssum, Netherlands
Dear Fer,
Forgive the pun, but draughts
seems to have been left out in
the cold by comparison with
that other board game, chess. /
must admit, I'm not aware of
any good draughts programs for
the Spectrum, so, any producer
reading this please let me
know if you have a draughts program.
You could try modifying
the listing in 'Basic Computer
Games' by David A hi for the
Spectrum, but / doubt whether
that will offer much of a
Challenge for an experienced
player.
Crash!
Dear David,
I'm trying to write a simple
machine code routine on the
2X81 which involves places
characters on the screen. The
program starts to work, but then
crashes; what could I be doing
wrong?
Simon Harrison,
Manchester
Dear Simon,
There are lots of things that
could go wrong with your
machine code routine, and my
machine code series may help.
But as your routine actually does
something before crashing, then
/ suspect that you are inadvertently
changing the value
of the NEWLINE character
which exists at the end of each
row on the screen — that's
always good for a crashI
In the fully expanded display
file (with less than 3.5K of RAM
the ZX81 contracts the display
file to save space), there are 33
characters per row; you've probably
overlooked that extra
NEWLINE character.
ZX COMPUTING APRIL/MAY 1 98 5 111