Despite using a Z80
processor instead of the BBC micro's 6502 Sir Clive Sinclair's
new lap-held computer, the Cambridge Computers Z88, is surprisingly
compatible with the BBC machines. The programming language
is Z80 BBC Basic and the word-processor cum spreadsheet, Pipedream,
was written by Mark Colton, the author of View, and is almost
identical to Acornsoft's View Professional.
Other "applications"
and "popdowns" supplied on the Z88's rom are a VT52
Terminal, Diary, Calculator, Calendar, Real Time Clock, Alarm
and File Import-Export Software.
Compatibility
Before describing the machine in detail
it is worth looking at that compatibility. Pipedream working
files are indistinguishable from View Professional files so,
provided that you have View Professional on your BBC, files
can be transferred either way and editing continued on the
other machine. This is particularly handy if you want to see
a Z88 document on a larger screen before printing.
The Z80 processor BBC Basic and the normal
6502 BBC Basic are very similar. Unfortunately although the
command tokens are the same programs are stored differently
so a directly transferred Basic file will not run on the other
machine. The translation is not too difficult though. BBC
files start with a carriage return, Z88 ones don't. BBC files
end with &FF, Z88 ones with &00,&FF and &FF.
The three bytes after each carriage return are i n the reverse
order and you can't always have leading spaces in a Z80 BBC
Basic statement.
The main difference between the two Basic
languages is that Z80 Basic writes files in text form, whereas
the 6502 version uses its own internal format. Additionally
on the Z88 the graphics, sound and analogue commands are missing
(ADVAL, CLG, COLOUR, DRAW, ENVELOPE, GCOL, MODE, MOVE, PLOT,
SOUND) and the built in assembler is for the Z80 processor.
Commands like VDU, OSCLI, CALL and USR are
still there but they will not necessarily have the same effect.
Indirection operators can be used but as memory is allocated
dynamically it is unwise to use them with absolute machine
addresses.
As the Z88 implementation of Basic does
not have a line editor or, indeed, any other edit facility
it can be advantageous to write and debug a program on the
BBC and then export the finished program to run on the Z88.
The only way to change a statement in Z88 Basic is to retype
the entire line.
Hardware
So to the Z88 itself. It is a few millimetres
smaller than this magazine and about 20 millimetres high.
It weighs just over 2 pounds and runs on on four penlight
batteries. The batteries on an unexpanded machine are claimed
to last for 20 hours of continuous processing or a year of
preserving memory. My experience has shown this to be a reliable,
and maybe conservative, estimate.
The Z88 has a two stage way of warning you
that the batteries need replacing. Fist an indicator that
they are low comes on at the right hand side of the display.
Later the machine shuts down to allow all remaining power
to be used to keep the contents of memory safe.
The 100 column by 8 row liquid crystal display
is remarkable. Remarkable because of its clarity and the wide
angle over which it can be comfortably viewed. The keyboard
is made of rubber which is very quiet and surprisingly pleasant
to use. It does get dirty quickly but can easily be cleaned
with a damp cloth. If I were to criticise the construction
I would question whether the keyboard rubber is attached to
the body of the machine firmly enough.
The machine comes with 32k of ram, of which
about 18k is available to the user. The use of this is split
between applications and file storage. Three slots at the
front allow you to add ram and eprom cartridges in 32k and
128k sizes. 1M ram cartridges are promised but as yet are
not available. The ram cartridges are not just backup store,
as the Z88 will use the whole of available memory dynamically
for applications or filing.
As you would probably guess, for most sensible
uses of the machine you are going to need at least 32k of
extra ram. The built in memory has about enough space to save
two pages of A4 from Pipedream to the filer for transmission
to the BBC, provided there's not much else inside the machine
at the time. By using a 128k card it is possible to create
documents in Pipedream which are too large to be loaded into
memory in the BBC, even in a shadow mode.
Communication in and out of the machine
is via The RS232 socket, a 9 pin female 'D' connector to the
right of the keyboard. Next to that is 20-way double sided
edge connector which, we are promised, will allow a disc drive
and other extensions to be fitted at a later date. Using my
BBC micro as well I am not sure that I'd want a drive on this
machine as I have been using the BBC for long term storage
of files. I suppose a disc drive to keep at home would be
useful backup if the Z88 were your only machine.
A serial printer can be attached directly
to the RS232 port or files can be transferred to the BBC for
printing.
Control
There are four keys which largely control
the action of the machine. The "Index" key allows
the applications and popdowns on the rom to be entered as
well as any suspended activities. The "Square" key
allows direct entry to any application or popdown from any
other. The "Menu" key will display menus appropriate
to the current activity and the "Diamond" key will
directly use a command within the activity. Thus the machine
can either be considered as menu driven (using "Index"
and "Menu") or as command driven (using "Square"
or "Diamond") depending on your preference. In practice
I used the commands when I could remember them, otherwise
I used the menus. As soon as I had learnt the scope of an
application from the manual I found that the menus were an
adequate prompt. On the Z88, unlike the BBC, you have to specifically
finish with an application to lose your work. For example
if you are using Pipedream and want to look at the Diary you
can press "Index" and select "Diary" (or
press "Square" D) and your Pipedream document goes
into suspension. When the index is next selected one of the
options you are given is re-entering that document, exactly
where you left off. These suspended activities can only be
deleted by resetting the machine or by selecting them in the
index and pressing "Diamond" KILL.
The difference between a popdown and an
activity is similar to that between language roms and service
calls on the BBC. An activity is the equivalent to a language
it takes control of the machine and can go into suspension
whilst a popdown is a utility which is performed but cannot
be suspended. You are not limited to one suspended activity
per application so you could have, for example, several suspended
Pipedream documents. The amount of free memory is the only
restriction on the number of activities that can be in suspension.
Of course with all these things in suspension
you need to be confident that the machine is stable. Pressing
the reset button (the equivalent of the BBC's "Break")
kills all suspended activities and alarms. Resetting does
not delete files but nevertheless you are likely to lose some
work.
In a month of use the only "crashes"
that I experienced were in Basic. If you do a machine code
call to a bad location the machine, not surprisingly, hangs.
More conventionally I was developing a program with error
trapping (using "ON ERROR GOTO ...") which hung
the machine when the program encountered unexpected errors.
This is another reason why it might be more practical to develop
programs on the BBC and then import them onto the Z88 when
they are working. If you are developing programs on the Z88
using the Z80 Assembler a sensible precaution would be to
save any suspended activities to files.
Pipedream
As Pipedream is the major application on
the Z88 it is worth a closer look. Although from the same
author as View it should not be seen an extended version of
that word-processor. Although at first sight it is a word-processor
with a built in spreadsheet in reality it is the reverse.
The slots, or columns, (equivalent to a combination of View's
ruler and Viewsheet's slots) have to be of constant size throughout
a document. When slots are used for text, reformatting does
take place with insertions but not with deletions. Thus adding
text which goes over the end of a line will reformat the rest
of the paragraph but text will not be moved up after a deletion.
As with View you have to manually reformat in these circumstances.
By default Pipedream works in insert mode
without justification but this can be changed on the options
page. Like View a Printer Driver is still needed but has 8
highlight codes. A Printer Driver Editor is on the Z88's rom
as an application. Macros are not supported so mail-merging
is not a practical possibility.
The built in spreadsheet allows for useful
integration. For example it is very easy to type invoices
and add them up within the document. Also there are a number
of simple database instructions so, for example, you can sort
a marked list of names into alphabetical order.
The underlying slot structure makes it very
easy to type text in columns, where on most word-processors
you have to be constantly changing rulers.
Use
Until I tried using the Z88 I would have
thought that a portable computer was of little practical value
but I quickly found it indispensable. I found it particularly
useful for typing in documents when I had a spare moment,
later transferring the files to my BBC for printing. On the
BBC micro View Professional has its limitations as a main
word-processor but in its Pipedream form on a portable I found
the facilities more than adequate.
The machine is smart and slips easily into
the briefcase. The diary facility is useful (particularly
as you can do searches through it to find, for example, all
unpaid expenses). Pipedream is very powerful and, with View
Professional on the BBC, totally compatible.
This is not a gimmicky machine but
one with highly usable facilities at a reasonable price. Once
you have used one you will wonder how you ever managed without.
