It is rather tedious having to type programs in to the computer each time you
want to use it. The ZX Spectrum has the facility for recording programs onto magnetic
tapes with a normal, domestic cassette recorder. If you have a program in the
memory try to save it using the following procedure.
If
you can save programs on cassette tape you can load them back again
later.
Most
cassette recorders will work: as far as the computer is concerned, the
cheap portable mono cassette recorders are at least as good as expensive
stereo ones, and give less trouble as well. You will find a tape counter
very useful.
The
cassette recorder must have an input socket for use with microphones
and an output socket for use with earphones (if there is not one, try
the external loudspeaker socket). They should be 3.5 mm jack sockets
(i.e. to fit the jack plugs on the leads provided), because other sorts
often do not give a signal powerful enough for the computer.
Any
cassette tape should work although low noise tapes may be better. Having
acquired a suitable cassette recorder, connect it to the computer using
the leads supplied with the ZX Spectrum: one lead should connect the
microphone input socket on the recorder to the socket marked 'M I C'
on the back of the computer and the other should connect the earphone
output socket on the recorder to the 'EAR' socket. (You cannot harm
the ZX Spectrum by connecting the cables incorrectly).
When
you are using the SAVE command to store a program onto tape,
you must make sure that one of the plugs of the lead connecting the
'EAR' sockets on the computer and cassette recorder is pulled out -
either of them will do. If you forget to do this you will get nothing
more than a steady note recorded onto the tape, which 'IS useless. The
reason for this is that when the cassette recorder is recording it amplifies
the signal coming in on its 'MIC' socket, and puts it out on the 'EAR'
socket. If this gets back into the computer it will form a loop, which
will oscillate, smothering the signal you were trying to record.
Type
some program into the computer, say the squares program in the previous
chapter, and then type:
SAVE
"Squares" Squares
is just a name that you use to label the program while it is on tape.
You are allowed up to ten characters in the name which must consist
of just letters and numbers.
The
computer will have come up with a message Start tape then press any
key. We shall first go through a dry run so that you can see what
happens: do not start the cassette recorder, but press a key on the
ZX Spectrum and watch the border of the TV screen. You will see patterns
of coloured horizontal stripes.
5
seconds of red and pale blue stripes, about 1 cm wide and moving slowly
upwards.
A
very short burst of blue and yellow stripes.
1
second with everything as normal.
2
seconds of the red and pale blue pattern again,
about
1 second of the blue and yellow pattern again.
Try
it again until you can recognise all these. The information is saved
away in two blocks and both blocks have a lead-in corresponding to the
red and pale blue pattern, and the information itself, corresponding
to the blue and yellow pattern. The first block is a preliminary one
containing the name and various other bits of information about the
program, and the second is the program itself together with any variables
present. The white section between them is just a gap.
Now
let's actually capture that signal on cassette tape.
1.
Position the tape in a part either that is blank, or that you are prepared
to overwrite.2.
Type
SAVE
"Squares" (and ENTER)
3.
Start the cassette recorder recording.4.
Press any key on the ZX Spectrum.5.
Watch the television as before. When the computer has finished (with
the report 0 OK) stop the cassette recorder.
To
make sure that this has worked, you can check the signal on the tape
against the program in the computer using the VERIFY command.
1.
Turn the volume control on the cassette recorder to approximately half
way and reconnect the 'EAR' lead.2.
Rewind the cassette to somewhere before where you started to record
previously.3.
Type
VERIFY
"Squares" (VERIFY is extended mode, then shifted R).
4.
Start the cassette recorder playing.
The
television border will alternate between red and pale blue until the
tape reaches the recording you made; then you will see the same pattern
as you did when you saved the program. In the one second gap in the
middle, Program Squares will be written on the screen - when
the computer is searching for something on tape, it prints up the name
of everything it comes across. If you see all this pattern and then
the computer stops with report 0 OK your program is safely recorded
on tape and you can skip the next few paragraphs. Otherwise, something
has gone wrong. Go through these questions to find out what.
Making sure your programis saved
Has the name come up?
If not then either the program was not saved properly in the first
place, or it was, but was not read back properly. You need to find
out which. To see if it was saved properly, rewind the tape to just
before where you started recording, and play it back through the tape
recorder's own loudspeaker (you will probably have to unplug the lead
from the earphone socket on the tape recorder). The red and pale blue
lead-in gives a very clear, steady high pitched note, and the blue
and yellow information part gives a much less pleasant sound, like
a morse code message in a hurricane. Both of these are quite loud
- at full volume they can easily drown conversation.
If you do not hear these noises then the program probably did not
get saved. Check that the right leads are plugged in the right sockets.
Make sure that the 'MIC' sockets are connected, and that the 'EAR'
sockets are not. It happens with some tape recorders that the jack
plug does not make contact if it is pushed right in. Try pulling it
out about a tenth of an inch - you can sometimes feel it settling
down into a more natural position. Also check that you were not trying
to record on the plastic leader at the beginning of the cassette.
When you have checked these, try saving again.
If you can hear these sounds as described then SAVE was probably
all right and your problem is with reading back.
Check the leads again, and also check the volume level. If it is too
quiet the computer will not hear the signal properly, and you will
not see the right patterns on the screen; if it is too loud the signal
will get distorted - you may be able to hear it coming through the
computer's own loudspeaker. There is a wide range of acceptable values
in between, but you could try experimenting. The next case is when
the computer finds the program and writes its name up but still goes
wrong. Some possibilities are:
You mistyped the name, either in SAVE (when the computer will
write the mistyped name on the screen) or VERIFY: the computer
will ignore the program and carry on flashing red and pale blue as
it goes.
There is a genuine mistake on the tape: the computer will come back
with R Tape loading error, which means in this case that it
failed to verify the program. Save it again.
It is just possible that the volume setting on the tape recorder is
not quite right,- but it cannot be far wrong because the computer
managed to read the first block
|
Now let us suppose that you have saved the program and successfully verified it.
Loading it back is just like verifying it except that you type
LOAD
"Squares" instead
of
VERIFY
"Squares" LOAD
is on the J key. Since it verified properly, you should have
no problem loading.
LOAD
deletes the old program (and variables) in the computer before loading
in the new one from tape.
Once
a program has been loaded, the command RUN will run it.
It is
possible to buy pre-recorded programs on cassette. They must be specially
written for the ZX Spectrum: different types of computer have different
ways of recording programs, so they cannot use each other's tapes.
If your
tape has more than one program recorded on the same side, then each
will have a name. You can choose which program to load in the LOAD
command: for instance, if the one you want is called 'helicopter' you
could type
LOAD
"helicopter" (LOAD
"" means LOAD the first program you come across which can
be very useful if you cannot remember the name of your program.)
|
|
