News & Reviews Index > Ace Review Computer Answers Nov/Dec 1982

Jupiter Ace review Computer Answers Nov/Dec 1982 page 7
The Jupiter Ace, with its Sinclair-like price and design,
offers a cheap opportunity to get into the language Forth.
But is it an opportunity worth taking?

There are many reasons why people buy a cheap micro. It might be to learn programming or to extend programming expertise, it might be to play games, or it might be for 'serious' applications, such as stock control, or regression analysis.
Many parents buy micros for their children to play space invaders. The children and parents become interested in programming; and then the adults start to use the micro for practical things they had not imagined at the outset.
How does the Ace fit into this scheme, as a cheap micro?
The answer is that it does not fit easily into any scheme - it is a very different machine. Given the present state of the micro market, the Ace has two big question marks: one, it is not a colour computer and two, it does not use a variant of the common language Basic but uses instead a language called Forth.
If you want to buy a computer to play games, and that is all your are really interested in, this is not your machine. Forth is completely different to Basic. It has been principally used for 'serious' applications. This means that there are no listings of Forth computer games which one can conveniently copy. The Ace is unlikely to have many suppliers of software for some time, so you will be left to your   own   devices   or   to  software

provided by Jupiter Cantab.
Jupiter Cantab means Richard Altwasser and Steven Vickers, (designers of the Sinclair Spectrum). The software for the Spectrum produced by Altwasser is very expensive and not very good (I refer to the Cambridge Colour Collection).
In an attempt to get Forth users to buy the Ace, and write software for it, there's a special deal for members of the Forth Interest Group (FIG). If a FIG member buys an Ace, he or she will be entitled to a £5 reduction on the following year's membership fee.
When we come to those who want to buy an Ace to learn to program, the language is Forth, and though there is nothing wrong with Forth - in fact it has much to offer - help is not so plentiful. So far there is only one book which attempts to introduce Forth (most books assume some knowledge), and that is Starting Forth by Leo Brodie; and so the novice (or not so novice) who wishes to program will have to depend on the manual provided with the Ace.
Most manuals to accompany Forth on other micros are either incomprehensible, or insubstantial, and Brodie's book takes about 350 pages to only go a small way. For Forth, on a micro which cannot run Basic, the manual is extremely important, and good manuals are difficult to write.

Jupiter Ace review Computer Answers Nov/Dec 1982 page 8

Once the purchaser of the £90 Ace has learnt to program in Forth, then the Ace can be used for serious purposes (including writing games software). The graphics capabilities of the Ace are fair, though not in colour, and the user-defined graphics are simple to use (once one knows how to program in Forth). The special version of Forth developed for the Ace is very easy to use, as Forth goes.
The cassette operating system is simple to use and has many affinities to that for the Spectrum, and the whole Ace Forth environment is very stable - something not true of most other Forth systems on micros. A game written for the Ace might run more quickly than that on another micro programmed in Basic; but machine code is swifter still, and the Ace program will be in black and white only.
Forth is a very different language. It was designed for control applications such as pointing telescopes in the right direction, or operating robots - it is designed to produce exceedingly fast-running programs. This, therefore, is one serious application for which the Ace should be best suited.
To run a robot, or a model, requires the Ace to talk to the robot via some communication device, but the Ace, unfortunately, only has ZX81/ZXSpectrum style of hole in the back where you can plug things in - it is not a standard interface that you might use for control applications. The keyboard on the Ace looks remarkably like that of the Spectrum, and the machine as a whole gives the impression of being a ZX machine-not
substantial enough to use in a dusty factory.
The Ace might find use as a demonstration machine to show how one might use a Forth computer to control applications-but that is possible with the BBC computer-or the Ace might be used for the two examples given at the beginning, stock control or regression analysis.
For stock control the Ace is not suited, because the speed of Forth is not essential-the speed at which data can be accessed off the storage medium is far more important-given that this is the case, there are many machines (eg the Spectrum) for which the programs are easier to obtain.
In regression analysis the key problem is the accuracy with which the fractional numbers can be stored. Ace Forth does have fractional (or 'floating-point') numbers but they are of limited accuracy (only six digits) -even the ZX81 is more accurate.
The memory available on the Ace is rather limited, though it is possible to use the Sinclair 16K RAM Pack, and so the Ace can only tackle medium-sized problems. For those who would like to see a line of Forth, the Forth words to emulate the Basic command X = X + Y are X @ Y @ + X! You can see why the usual cacophony of books originally written for the ZX80, and changed for each new computer, will not appear-and how dependent one is on the manual and software from Jupiter Cantab.

*Further reading: Starting Forth by Brodie, Threaded Interpretive Languages by Loeliger.
*Forth Interest Group, 38 Worsley Road, Frimley, Surrey GU16 5AU.