Portable Micro Looks Sharp

Camilla Martin looks at a briefcase-size portable with tape and printer from Sharp

The first thing that strikes you about the new Sharp MZ731 portable is how few pieces it consists of. It's made of lightweight, durable plastic, and comes as a standard keyboard with integral plotter, speaker and cassette recoreder.

The whole ensemble is some 17" by 3" at the back, the height tapering to a couple of inches at the front. It's highly portable, weighing less than the average briefcase, and is easily tucked under the arm.


The manual provided is adequate, and includes the now fashionable cartoons to lighten the subject matter.

For the first time there is an extensive briefing in S Basic with explanations of each function, and an appendix listing reserved words. However, the format of this section brings up the debate about how best to instruct a beginner. You could get them used to making their particular type of machine work - in this case cassette loaded programs and the commands specific to Monitor 1Z-03A - or you could teach them the rudiments of the structure behind storage and retrieval of information.

If you feel strongly about the latter, perhaps because you intend to upgrade to a less portable but more powerful machine later, then this won't be the tool for you.

The Basic has its own monitor program which greatly extends the power of the machine by allowing you the use of machine code programs, and which has a text editor that follows the same type of screen editor as Basic. This familiarity will cause few problems - although it is not extensively documented. Neither are the machine code commands and a novice programmer might well find the sample program completely baffling. I think it assumes perhaps too much knowledge on the part of its readers.


The Sharp is up to the usual high construction standards of Japanese products, and comes as a single, compact unit. At the top left hand corner, next to the plotter and cassette recorder, is a three inch square ventillation grill. The speakers for the internal sound are location underneath this. Sound for these is controlled via Basic commands.

There are nine major sockets and connections on the back of the machine, including a power switch, colour on/off switch, a fine-tuning colour trimmer, a reset button and a volume control for the speakers. The latter is a little exposed, and difficult to manipulate.

There are two metal plates screwed onto the back, behind which are the printer and I/O sockets. The I/O appears to be a bus, but it actually a board edge connector rather than a proper connector. On the left hand side there are two sockets for connecting your TV/monitor to. The first is labelled 'video' and give rather wobbly displays towards the bottom of the screen, together with fairly dodgy colour. The other, labelled 'RF', gave a stable screen and clear colour.

In between the TV sockets are the channel volume switch and the colour on/off switch. Next door to the recess housing these four is an RGB signal output DIN connector for use with the Sharp MZ1D04 monitor. Beneath these outputs are the read and write sockets supplied to connect to any standard external tape recorder. On the right of these is a plastic covered connection socket allowing joysticks to be connected.

The on/off switch is handily positioned on the extreme right of the machine's rear, the reset being less well-placed more centrally on the back-plate. The machine also has a Frame Ground terminal output just below the power socket. Sharp has clearly left little to chance as regards I/O. The RF, however, does not allow you to send sound through your TV set.


The keyboard has the standard qwerty format, but it is dominated by one horrendous problem. It is rigged with shift the wrong way round, so characters come out caps locked unless you ask them *individually* not to. To do this you use the shift-function key... which you can't lock. This is no doubt handy for Basic programming, but useless for text writing. It's no surpirse that there's no mention of word-processing in the manual.

In addition to the ordinary but upside down shift, there are two further shifts which allow access to a wide range of block graphics, two per key. There are five blue function keys at the top left, and a cluster of four cursor keys to the right of the main keyboard. The break key is situated at the top right, safely out of harm's way.

Immediately below the tape deck the delete key is raised largely than life in a separate batch of two keys above the rest. The keyboard itself has several modes of operation. It can be used for text editing, and then switched over to graphic characters, which are depicted on the left side of the front vertical face of each key.

Use shift with this mode and you will see the character shown on the right side of this face. It sounds alarming, but all graphic options are actually visible at all times, despite this description.

To switch from one mode to the other two keys are added - Graphics and Alpha. Alpha denotes alphanumeric, in case you were wondering, although 'text' might have been easier to understand to the uninitiated. At the top are the five 'function' keys which can be set to any definition by use of the DEF KEY Basic statement explained in the manual. Initially they will be preset to certain common commands, such as RUN+CHR$(13) [carriage return], LIST and AUTO, which are programmed when Basic is loaded into memory.


Eight colours (excluding black and white) are available - the seven colours of the rainbow excluding orange, with pale blue replacing violet. But blending routines can be developed to allow a far, far wider range of shades to be produced. There seems to be somewhere in the region of 100 of these available.

A demonstration program called 'Openings' is supplied with the machine, and this shows off the graphics, sound and most particularly the colour capabilities superbly. Within the Basic listing is encoded a call to an assembler subroutine for overlaying the eight colours in turn to produce subtle shades, but there is no documentation of this in the manual.

In order to set any of the colours, you first have to set four parameters - an x and y coordinate for the character, the character colour and the background colour, in the format COLOR (or COL.) X,Y,C,B, where C and B represent numbers specified in the manual.

If you wish to specify a colour for all characters, a comma bypasses the unnecessary coordinates (e.g. COL. ,,C,B). You can set the display colour alone by typing COL.,,C,, and the background by typing COL.,,,B.


A cassette recorder with the standard key format is built-in on the top right hand side of the machine. It's operated simply by typing LOAD then pressing play. It seems fairly reliable, and every tape I tried loaded first time. However, the cassette operating system - if it can be called that - is very weak.

There is no provision for anything more than the most rudimentary of filenames, no header block which could be used as a directory, or anything in the way of motor control.

There's no mention of disk drives coming up - indeed 'or floppy disk' had been carefully inked out of the manual - and there's very little information on add-ons in general, or recommendations about the software that can be run on the machine. The review 731 came with just two short cassettes housing three programs, including the Basic language. The implication appears to be that you should create your own!


The plotter/printer is the only part of the initial setting up that might case problems, and unfortunately the relevant section placed in the middle of the book. The index points the way of course, but it would surely have been better to have this piece nearer the closely-related section which talks you through starting up the machine, particularly as every encouragement is made to use the printer right through the manual.

As it is, I'd barely executed a couple of programs before I was itching to try the plotter. This consists of a small print-head that looks like a bundle of pencils, and is capable of producing 80, 40 or ten character widths in four different colours: blue, black, green and red. It prints onto continuous paper which feeds back through a slit beyond the cover. Printing with the cover in place is therefore feasible - a nice touch.

If you leave the pens unused for a couple of days or so, they seem to have a tendency to dry up. You then have to remove them (using the eject lever described in the manual) and use them by hand to get them going again. The principle of the swivelling print head seemed to work well, though perhaps not in the manner you'd expect.

When commanded to swap colours part-way through the line, the head scuttles back into the recesses at the left, and there twirls to present a new pen, accompnied by noises like a small creature feeding, before sliding back out to its previous position.

However, I gave it some hours worth of printing to cope with, and it didn't falter. It is capable of graphics, but trying to print out graphics forms in text mode leads to the Hex equivalent being sent across in a different colour (usually blue). When using the printer in graphics mode, repeated lines may well become rather blurred, apparently due to the use of ball-pens, so double line spacing is advisable.

The commands to switch the printer between text and graphics modes are simple directives such as: M. TS to mean text, and M. GR for graphics. Similarly, there are easy commands for selecting which coloured pen should follow (black is the initial one) telling the printer to LIST some program or PRINT a string, for example: PCOLR 3, LIST/P, PRINT/P (with various length settings).

In all cases there are abbreviated formats, like PC. 3. The manual encourages its readers to use at least the text printer as soon as possible. After listing a couple of programs on the printer you are ready to tackle the mysteries of graphics.

Here the manual is not so kind. From sitting distractedly looking from book to screen (which always breaks concentration) and half anticipating the simple leading in functions, you are pulled up with a lurch to find talk or relative coordinates and relative distances from variable origins.

Operating System

Since the computer is referred to by the manual as 'clean', meaning that no language is fixed into the memory when you switch on, it is necessary to pick up the rudiments of the operating system. This is a small (4K) program, sitting in ROM, which has a very few actual commands. Those it has must be augmented by calls to machine code subroutines.

It is called Monitor 1Z-013A, not to be confused with the Basic monitor program, and its call-instruction set it to be found a good way through the manual in chapter five. There is a useful index of these calls in the appendix, along with notes on the general use of software and hardware.

Under the Monitor function it is possible to address the machine's memory directly, at the same time calling in predefined routines. At the very back of the manual are several pages concerned with Z80A assembler listing, its instruction set and the program list with comments.


As far as connecting external devices is concerned, the chapter which offers guidance on connecting to a monitor display or TV set goes on to discuss the other peripherals. In turn it spells out clearly what to plug in where for a separate printer or cassette recorder, often referring to its own makes of each. The software/hardware notes at the back of the book issue warnings about using other makes.

However, on the wiring side, the manual assumes other sources of information will be available and merely provides an unexplained configuration signal diagram further on. This is set amongst circuit diagrams which are a bonus for the technically minded, but overall I do not think enough information has been provided to make the going easy for add-ons.


The market I feel the Sharp has been designed for is the keen beginner, or the first time buyer who has a little experience of Basic program writing. For both it holds out the promise of developing their technique while keeping the format simple, with the minimum of add-ons.

As portables with their own printing devices go, I liked this little machine. It looks stylish, surpassing the 'tinniness' of metallic coloured models, and it doesn't feel too light and brittle.

It is potentially a fairly versatile machine, but it would be wise to bear in mind the fact that there seems to be very little software available at present. Until this changes, it's therefore likely to be more suitable for the enthusiast.


Machine: Sharp MZ731 with built-in cassette and colour plotter
Price: £419.85
Processor: Z80A
RAM Memory: 64k
ROM Memory: 4K plus 2K character generator
Text Format: 40 x 25, 8 colours
Keyboard: 59 keys plus five functions and four cursor keys
Storage: Cassette
OS/Language: Tape-loaded, interchangeable
Distributor: Sharp 061-205 2333
Software Included: Demo tape, S Basic