Reviewer: Tim Hartnell
Magazine: Your Computer
Date: January 1982
Predicted sales of the BBC Microcomputer have mushroomed from an original estimate of 12,000 to possible orders of 100,000 during 1982. Tim Hartnell assesses one of the first of the £225 systems to leave the production line.
The BBC microcomputer is a joy to use, with flexible colours and an incredibly fast Basic of its own which has more facilities than you are ever likely to use. I must qualify this glowing praise by pointing out that the review machine was a pre-production model. One may take for granted that some of the facilities it lacked will be present in the commercially available model.
The BBC Microcomputer looks, at first sight, like an extended Atom, with a broader area behind the keyboard. There are 10 user-definable function keys at the back, but no separate numeric pad. The keyboard is very sensitive, like a good electric typewriter - as the BBC specification demanded - but the model I used was almost too sensitive and led to inadvertent double-striking time after time. The keyboard means touch-typists can program as fast as they can type, but I feel Acorn have overdone the sensitivity a little.
The processor is a 6502A, operating at 2MHz. The review computer was running at half speed, but was still extremely fast. When I converted one of my Life programs, written in Basic and which takes about 20 seconds a generation on the ZX-81, about four seconds a generation on the Atom, I found it took about 1.5 seconds on the BBC machine - speed indeed.
In a more formal test of the machine’s speed, I ran a simple loop - count from zero to 1,000, printing out each number during the loop - on the Atom, the MZ-80K in Basic and in Pascal, and on the BBC machine. The result were:
- Atom - 1 minute 23 seconds
- MZ-80K, Basic - 50 seconds
- MZ-80K, Pascal - 22 seconds
- BBC Microcomputer - 14 seconds
The Atom time is so bad because the routine to Print takes a good deal of time-consuming care to keep the display snow-free.
The BBC Micro’s Basic ROM occupies 16K, and the machine operating system a further 16K. The BBC says much of its software will call up monitor routines. There are two computers in the range, model A, which will sell for around £225, and the more flexible model B - around £335. The review machine was a model B.
The 73-key keyboard has the full QWERTY layout, the user-definable function keys, four cursor-control keys in the top right-hand corner marked with arrows, two-key rollover and auto-repeat.
The display is very flexible, but I feel the designers have made some very peculiar decisions. There are eight display modes, with zero to three available only on the more extensive model B. The graphics modes are:
- Mode 0:
- High-resolution - 640 by 256 - two-colour graphics and 80-by-32 text. Mode 1: High resolution - lower, in fact, 320 by 256 - four-colour graphics and 40-by-32 text.
- Mode 2:
- 160 by 256, 16-colour graphics and 20-by-32 text. This is where I feel one strange decision has been made. The only mode which gives access to 16 colours has a very broad text of 20 characters across which is almost unreadable without a full blank line between each line of text The colours in mode 3 are superb and because of the wide range, this is the mode most model B owners will probably prefer. After all, 160 by 256 for graphics is an acceptable degree of resolution. Yet because the text is so broad - is it designed to be read at the back of classrooms? - the use of mode 2 will be somewhat restricted.
- Mode 3:
- 80 by 25, two-colour text.
Model A supports only modes 4, 5, 6, 7 which are also, of course, supported by model B. The additional modes are:
- Mode 4:
- 320 by 256, two-colour graphics and 40 by 32 text.
- Mode 5:
- 160 by 256, four-colour graphics and 20 by 32 text.
- Mode 6:
- Two-colour text.
- Mode 7:
- Standard teletext display.
The colours you obtain in the two-colour mode are either black and white or certain pairs which you can call up with a command called VDU. The four colours are black, white, orange and yellow, but these can be changed using VDU.
The text, except for the broad mode 2, is very clear, with added extras such as a true ½ and |, plus little arrows, lambda, square root, a proper division sign and “approproximately equal to”. The character set can be easily redefined using the VDU command. The character set, with a few of the control characters, includes:
|12||Clear screen and home cursor|
|30||Home cursor without clearing screen|
|31||Move cursor to specified location - used as PRINT CHR$(31),X,Y|
|157||Reverse colours of a single line|
|48 to 57||Numbers 0 to 9|
|65 to 90||Upper-case letters A to Z|
|97 to 122||Lower case, with true descenders 255 Solid square, size of one character|
The review computer was feeding a monitor, so the colours were a little brighter and clearer than they will be on a domestic television. I tried the machine on my own television, and found that although there was a degradation compared with the monitor, the result was still perfectly satisfactory. The lower-case letters in mode 0 are, however, very difficult to read, except on a large television. Mode 0 puts 80 characters across a single line.
Room for expansion
The computer contains a three-tone music generator, which has the full envelope control of attack, sustain and decay, and which feeds an internal loudspeaker. The machine emits a quiet “beep” when you turn it on.
Model B is, as expected, far more flexible than the model A, and is equipped with a variety of I/O ports. There is a user eight-bit parallel input/output port, and four analogue inputs for games, paddles or control applications.
One of the real strengths of the Atom is the way it was designed as an opened-ended system, to accept a large number of peripherals. The BBC machine follows this lead, with room inside the case for adding such things as interfaces for floppy discs,
Econet or the cartridge ROM packs. A speech-synthesis unit will be available which will also fit within the case.
There is also space for a “tube” connector for connecting a second processor. The BBC computer is designed so it can be expanded to run with a second processor and considerably expanded memory.
All the units which will connect via the tube are still in the development stage and will not be available for some time. The BBC says the units will include a 3MHz 6502 processor with 60K of RAM, a Z-80 processor with 60K RAM running CP/M, and 16-bit processor with 128K RAM.
From these plans it is clear that the BBC Microcomputer has been designed with an eye to the future, to ensure it does not become obsolete quickly.
The second 16K language ROM contains a 6502 assembler along with the Basic, as does the Atom ROM, so Basic and assembler may be mixed within a program. There is space within the computer for up to four 16K language ROMs which are paged. ROMs under development include Pascal and a word processor.
The teletext display has all the features of standard teletext, including flashing and the double-height option.
The error messages are unambiguous and polite - what else could we expect from a
BBC machine? The error messages, in upper-and lower-case letters, include:
- Missing, at line 100
- Syntax error at line 100
- No such line - if you try to Goto or Gosub without a destination.
These are of great aid in debugging, as are Trace On, Trace Off, Trace X and Trace line-number.
The BBC machine shows evidence that a great deal of thought has gone into its creation, and demonstrates that Acorn has learned much from its experience with the Atom. Atom thinking permeates the machine, but the BBC machine design has weeded out the more idiosyncratic features of the Atom without sacrificing speed and flexibility.
The most notable hangover from the Atom is the use of the query “?” for Peek and Poke; its context determines which it is. For
example, in the following Basic statement
IF ? A = 9
suggests Peek, while
? A, 98
There are some very useful features to save programming time. These include Auto which automatically numbers lines, starting at 10 and incrementing by 10 unless another option is chosen. Renumber, used as a direct command, is virtually instantaneous, and renumbers Gotos and Gosubs as well as the line numbers. Unless another option is specified, Renumber starts at 10 and increments in tens.
Those familiar with Atom Basic, and with some other implementations of the language, will be pleased to find the BBC machine accepts the same abbreviations for keyboards as the Atom, such as
P.(PRINT) R.(RETURN) L.(LIST) G.(GOTO).
Many first-time computer users are understandably bewildered when they first unpack and connect up their new toy. Unlike a record player or a television, a computer generally does not do anything at all, and certainly never does anything impressive unless it is told to do so.
The BBC provides a cassette of programs marked “Welcome” which contains routines to help you have the computer up and running from the moment you manage to wiggle the seven-pin DIN plug into place. The initial package includes the computer, a two-metre long aerial lead for the TV or monitor, a computer-to-cassette lead, the “Welcome” cassette and a very comprehensive and surprisingly unstuffy manual. The cassette contains 16 games, and demonstrations, including Biorhythms and Clock.
The user’s guide is divided into four sections. The first part tells you how to connect up the machine, and includes some simple, but impressive, one-line demonstrations to show the flexibility of the graphics commands. The second part of the guide purports to be an introduction to Basic but, as the manual admits, is really too brief to be of much use for the absolute beginner.
The third section goes through BBC Basic, command by command, with sample program lines showing the command in context, and associated keywords. The associated keywords for Restore, for example, are Read and Data.
The final part of the guide is a meaty reference section, giving an outline of the operation of the built-in assembler, the machine operating system, and such things as a memory map. Further technical manuals are planned to expand the information.
- The BBC Microcomputer is a splendid machine, with many avenues for exploration.
- Acorn and the BBC have done their work well, producing a machine which is better than the market demands - it is even over-specified. By doing this they have ensured they will probably not be able to meet the demand for the machine once word travels as to how good it is.
- They have also ensured that it will not become obsolete quickly, and they have earned the undying hatred of every other manufacturer of £200 micros.