News, Reviews and Letters Index > The Home Computer Course Review

   The Home Computer Course was published in the UK as a part-works, over 24 weeks covering all the microcomputers at the time back in 1983. The Ace made an appears in the Hardware Focus section in issue 8. The article has an error it reports the Aces clock speed as 1Mhz which is wrong and is in fact 3.25Mhz.

The Home Computer Course page 150
Hardware Focus


The only low-cost home
computer to feature Forth
instead of Basic as its
standard programming
language - a challenge for
ambitious programmers

Jupiter Ace Keyboard
The 40 moving keys are moulded from one sheet of rubber- much like the Sinclair Spectrum. The top row of keys all have three functions, which are accessed with the SHIFT and SYMBOL SHIFT keys. In addition, seven graphics characters (plus 'space') can be used to construct simple diagrams and graphs
The Jupiter Ace is an enthusiast's machine, and one of the few computers that does not have BASIC as its standard language. Though production was discontinued in 1983, devotees keep up a brisk trade in the Ace and its software.
   The built-in language is FORTH and is the distinguishing feature of this machine. But the hardware is cheap enough for anyone who is interested in learning FORTH to buy the Ace rather than upgrade their existing computer. The computer comes with a manual that is an excellent tutorial on FORTH.
   The Ace is laid out very much like the Sinclair models. In fact its case is the same white, flimsy plastic that the very first Sinclair computer (the

The Z80A has been used - not surprising as the machine's designers were responsible for the Sinclair Spectrum, too
  Introducing Forth

BASIC Version
110 FOR X=1 TO 6
130 NEXT X
140 END

FORTH Version
: SHOUT ." SHAZAM! " ;

Both the above programs will do exactly the same thing, but the BASIC version resembles a recipe, while the FORTH program looks like a wizard's spell!
FORTH starts with a collection of command words (called the dictionary), and has the ability to learn new words. In our FORTH program two new words are added to the dictionary: SHOUT is defined as a character string to be printed and CHORUS is defined as a mixture of 'primitives' (pre-defined words in the dictionary) and the new word SHOUT.
   FORTH also has a memory (called the stack), and the ability to process the numbers in it. The FORTH program does the same arithmetic and logic as the BASIC program, but by manipulating the stack instead of through algebraic expressions.
   FORTH is an infuriating' Rubik's Cube' of a language; it is also a powerful programming method, and a whole new way of thinking. Some programmers love it, some hate it.
   It is the ability to define and use new command words that really gives FORTH its power. Effectively, the user can tailor the programming language to suit the application he is implementing. FORTH is particularly suitable for programming domestic robot devices, for example, because the programmer can build up his own dictionary of commands: MOVE, FETCH, FIND, FOLLOW and RETURN for example.

This is a solid-state piezo- electric device (much like the bleepers found on digital watches), which can be used to generate simple sounds

Keyboard Pads
When a key is pressed, the special rubber material, which conducts electricity, makes a contact between two sets of metal tracks on the printed circuit board

The Home Computing Course page 151
Hardware Focus

Memory Expansion Port
With a suitable adaptor, the Ace can also make use of Sinclair ZX81 expansion packs

FORTH Language
Two 4 Kbyte EPROMs have been used to hold the language. ROMs have to be ordered by the thousand, so EPROMs are used for smaller production quantities. The top of each EPROM has a protective covering, otherwise any ultraviolet light would erase the contents

User Port Suitable for a printer or other device

This drives the microprocessor at 1 MHz

RF Modulator
Provides black and white output only for a television

Cassette Port
One of the most reliable systems devised

Video Circuitry
Machines sold in larger quantities would have a specially-designed chip to do the same work as this collection of chips
  Jupiter Ace
Obtainable second-hand from £40
  215 x 190 x 130 mm
  3Kbytes RAM expandable
  externally to 51kbytes:8Kbytes
  Black and white, 32 x22 rows of
  text, 64 x 48 graphics
  TV connector, cassette, power
  (9v), two edge connectors; first
  has complete address and data
  lines from the processor, second
  has data and some selection
  Power supply in mains plug,
  cassette and TV leads
  Rubber keypad similar to Sinclair
  Spectrum but softer and less
  accurate. Keys have to be
  pressed dead centre. All keys
  have auto repeat and two shifts
  allow all ASCII codes to be
  Easily the best manual for a   small computer and would put   quite a lot of larger computer   suppliers to shame. The author   wrote both the ZX81 and the   Spectrum manuals. In 180   pages there is an introduction to   FORTH and a full description of   the Ace, both supported by   copious examples. The book is   available separately for £5.95.   The contents list annotates each   chapter, there are four   appendices giving quick   references to all the facilities   available and an index.

ZX80) had. There is a small solid-state bleeper that can produce a range of single tones, but with a greater knowledge of the Ace complex sounds can be produced. Like all the Sinclair computers, the Ace has a power connector, a socket for a lead to a television and two large connectors for any other special pieces of equipment.
The cassette has a simple two-jack socket connection, which is one of the most reliable cassette interfaces on any computer.
The display is black and white with 32 characters to a fine, although it has a graphics resolution of 64 by 48. Each of the characters can be redesigned by the user to create specific mathematical symbols or game shapes.
There is not such a pressing need as with other cheap machines to increase the amount of memory available. FORTH programs are usually quite short, so a surprising amount can be put into the standard 3 Kbytes of memory. To write larger programs, more memory is needed. Both 16 Kbyte and 32 Kbyte RAM packs are available, and an adaptor can be obtained that will enable the machine to accept most Sinclair devices. A Centronics printer interface, a sound box and a device to improve the 'feel' of the keypads can all be obtained.

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