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To get your computer working you will need a television set for a screen. Most people at home will use their ordinary colour or black and white television to show the pictures that the BBC Microcomputer produces. You will also need a cassette recorder.
If you have a high quality monitor (for example in a school) then it can be connected directly to one of the sockets on the back of the computer. To connect the monitor to the computer you will need a special monitor lead.
Assuming that you want to use your normal television set, then you can connect it to the computer using the aerial lead that is supplied with the computer. One of the plugs on this lead has a long central prong which fits into the socket on the back of the computer marked UHF OUT. The other end of the lead goes into the back of your television set in place of the normal aerial lead (figure 1). Don't worry about the cassette recorder for the moment.
Next, plug your computer into the mains and switch it on. It should make a short 'beep' and the red light marked CAPS LOCK should come on. The switch on the back of the computer is marked ON/OFF. Turn the television on too and let it warm up for a moment.
Probably all you will see on the TV screen at this stage is a "snow storm". Sometimes the screen will appear to be just blank. You will have to "tune" the TV so that it can receive the transmissions from the BBC Microcomputer. When your television is tuned correctly words will appear on the screen.
Your television probably has some push-buttons which can be used to select different channels. Often button number 1 is tuned to BBC1, button number 2 to BBC2, button number 3 to ITV and so on. It is best to tune a spare channel for the computer, for example channel 8. You can then use this for the computer without interfering with the tuning of the normal channels.
Different makes of television set tune channels in different ways. For some of them, you turn the same knob that you use to select the channel. For others, there are separate controls. In either case, you should depress a spare channel button and then adjust it, or the associated control, until you get a good picture on the screen. A message similar to
BBC Computer 16K
should be clear and sharp. Many types of tuning control indicate, approximately, the channel number that you are tuning to. The BBC Microcomputer transmits on channel 36. It will not be too difficult to find the right channel but you will have to tune the TV carefully to get a really clear picture.
After that, do by all means press every button in sight on the computer - you can't do it any harm at all. Usually it just keeps on saying
whenever you press the large key marked RETURN That just means that the computer does not understand your commands. Its fault - not yours!
You will see that if you hold any key down for more than a short time the character on the key appears on the screen, then there is a short pause, then the character repeats until you take your finger off again. On the whole, when pressing keys on the keyboard you should aim to press them briefly - unless you want this repetition.
Now you are ready to experiment. You might like to try some of the following to see what the computer can do, but first be sure to press the key marked BREAK This will clear the screen and get the computer ready for you.
Type in the following exactly as shown;
and then press the RETURN key. As you will see the command MODE 5 clears the screen and just leaves the > mark on the screen. > is known as the "prompt" and it means that the computer is ready far your next command.
Pressing the RETURN key tells the computer that you have finished the line you are typing and that you want it to obey your command. Before you press the RETURN key you can correct errors by pressing the key marked DELETE.
If the computer says Mistake then press the BREAK key and try again, starting with MODE 5.
Then type in each of the following lines - but don't forget to press the RETURN key at the end of every line. Don't worry if you make a mistake - it really doesn't matter!
If the computer says No such variable then you are probably pressing the letter O instead of the number 0.
As you will have gathered the DRAW command is used to draw lines while PLOT 85 and PLOT 86 are used to plot and fill in triangles on the screen. When using the graphics the points on the screen are numbered from 0 to 1279 (left to right) and from 0 to 1023 (bottom to top). They are rather like positions on a piece of graph paper.
Words can also be plotted in colours, as you will have seen. Clear the screen by typing MODE 5 and then type the following:
COLOUR 1 this is selects a red foreground
COLOUR 2 this selects a yellow foreground
COLOUR 3 this selects a white foreground
COLOUR 129 this is selects a red foreground
COLOUR 0 this selects a yellow foreground
COLOUR 130 this selects a white foreground
The computer can create sounds as well. Try typing this in:
and then press RETURN
That gives a rather simple, crude sound. It is also possible to alter the quality of the sound. Try this:
ENVELOPE 2,3,2,-4,4,50,50,50,127,0,0,0, 126,0
(This should be typed in as one line even though it may spill over to the next line on the screen just as it has on this page. The computer will treat it as being 'one line' when you press RETURN.) Now carry on with:
You will have to press ESCAPE to stop the effect.
Here's another one:
ENVELOPE 1,1,-26,-36,-45,255,255,255, 127,0,0,0,126,0
There is a whole section on sound later on.
Now get a cassette recorder connected so that you can load the demonstration programs into the computer from the cassette tape supplied in the WELCOME pack. For the moment just follow the instructions - we can sort out the "whys and wherefores" later.
You have to do two things before you can load the programs from the WELCOME tape: first get the right lead to connect your cassette recorder to the computer and secondly set the volume control on the cassette recorder to the correct position.
There are a number of different kinds of leads (figure 2). The connection to the computer is through a 7-pin DIN connector; a lead has not been supplied with the machine because there are so many connections to the many different cassette recorders in use. In many cases a standard 5-pin DIN to 5-oin DIN lead will be suitable, provided you do not want to use the motor control. If you want full motor control, take your cassette recorder to your nearest BBC Microcomputer dealer who will be able to supply a lead or make one up for you. Alternatively, take your cassette recorder and this book to a local hi-fi dealer.
Note: Although you may find the ideal cassette lead difficult to buy locally, many cassette recorders do have a standard 5-pin DIN socket and a standard 5-pin DIN to 5-pin DIN hi-fi lead will work with the BBC Microcomputer in many cases.
Figure 2 A range of possible cassette leads
You will need to select a lead with a 7-pin DIN or 5-pin DIN lead at one end. This plugs into the computer. The other end of the lead must have suitable plugs for your particular recorder. Note: a standard 5-pin DIN lead will work with many recorders but will not enable you to make use of the computer's ability to start and stop the cassette recorder automatically.
Having got the cassette recorder connected to the computer the only remaining thing to do is to set the playback volume on the cassette recorder to the correct level.
With the BBC Microcomputer the cassette volume control setting is not critical. However, a special procedure for setting the volume control correctly is incorporated into the first program on the tape.
Press the BREAK key and type in the following, exactly as shown
and then press the RETURN key. Next insert the WELCOME cassette into your recorder. If your cassette recorder has a tone control then set it to maximum 'treble' and leave it there. Now start the cassette recorder playing by pressing the PLAY button on the recorder. Then adjust the cassette recorder volume control slowly, until you get the message:
Your volume control is now properly
set. Please wait while the first
program is loaded
on the screen. This will give the minimum volume level. You should then increase the setting a little more. If you need to, you can rewind the tape at any time. If no message appears rewind the tape and play it again, increasing the volume control setting in larger steps, or check the cassette leads are correctly plugged in.
The system is very reliable, so if you have problems it may be that your tape recorder is at fault or that you have a fault in the computer. You are advised to contact your dealer.
Note: Each computer program is recorded on the tape as a kind of screeching noise. It's not meant to be listened to, but some cassette recorders have the annoying habit of playing the tape through the loudspeaker while the tape is loading into the computer. Everything depends on what is plugs and sockets are being used. It is possible to stop this on most recorders by inserting a small (3.5mm) jack plug into the socket on the recorder marked EAR. You could insert the ear-piece supplied with the recorder if that is more convenient. On other recorders you may have to insert a DIN loudspeaker plug, with no wire connections, into the socket marked LS to turn off the noise. Don't try turning the volume control down because then the computer will not be able to "hear" the tape either. The important thing to do is to try to disable the internal loudspeaker as described above.
Make a note of the volume setting on your cassette recorder and always use that setting when playing back the WELCOME cassette. You may need to use a different setting with other tapes that you have purchased or recorded yourself.
On the WELCOME cassette the volume control setting program is repeated many times at the beginning of the tape. With practice it is possible to save time by running the tape forward by about 2 minutes (once the volume control is set) and then begin playing the tape from this point, having first entered the command CHAIN "WELCOME".
When the first WELCOME program has loaded into the computer it will clear the screen and give you instructions.
The WELCOME pack includes a booklet which describes not only how to get the programs running but also what each of the sixteen programs does.
As time goes by, a whole range of 'application programs' will be available on cassette and it will be possible to run these in exactly the same way as the WELCOME package.
Anyone who has used a standard typewriter will be reasonably familiar with the positions of most of the symbols on the keyboard of the BBC Microcomputer. However, there are a number of special keys which need to be mastered (see figure 3) and these are described below.
If you are a keyboard 'novice' you may find the layout daunting. Don't worry - first of all it is not necessary to be a touch typist to work the computer; secondly, there is a program on the WELCOME cassette which will help you to practice finding the various keys, and most people find that with a little practice they become familiar with them fairly quickly.
Some keys have two symbols engraved on them - we'll call those on the top 'upper case' and those below 'lower case' symbols.
When the machine is switched on, the middle light should be on, telling you that the CAPS LOCK key is on. This gives capital letters and lower case symbols and is the most useful state for programming because the computer only recognises commands typed in using capital letters. By pressing the CAPS LOCK key once you can switch the light off. Now you get lower case letters and lower case symbols. Press it again and it will be on again.
Whether CAPS LOCK is on or off, if you press either of the SHIFT keys and hold it down while typing in a character you will get a capital letter or upper case symbol.
Holding down CTRL and SHIFT together stops the computer 'writing' to the screen. This can be useful if it is 'writing' faster than you can read.
Pressing this key once gives capital letters and upper case symbols until it is pressed again. It has its own on/off light.
Practice in the use of these keys is given in one of the first programs in the WELCOME pack - the one called KEYBOARD.
This key is the most commonly used key on the keyboard. When a command or anything else is typed in, it is not usually acted upon until the RETURN key is pressed. In other words, this key informs the computer that you have finished entering a line or a reply. Until you press RETURN , you can add to or delete what you have typed in.
These enable you to move the flashing cursor around the screen when editing a program. Pressing any of them makes the computer automatically enter the "editing mode" during which two 'cursors' are shown on the screen (see page 29).
Pressing this key will cause the last character typed in to be erased from the screen. If held down, it will then erase further characters until released.
This key, used in conjunction with the cursor control keys, enables anything on the screen to be copied - a useful feature when editing a line in program.
This key is usually used to stop a program which is running, however, it can be programmed to do other things when pressed - such as to move you from one part of a program to another.
This key stops the computer no matter what it is doing. The computer forgets almost everything that it has been set to do
Do not get into the habit of using BREAK. The ESCAPE key provides a much less violent way of escaping, from a program! (See page 142 for more details on BREAK).
This key behaves similarly to the SHIFT in that it can be used to change the character generated by other keys. For example, pressing CTRL and G (called Control G) makes the internal speaker make a short noise. CTRL B is used to turn a printer on and CTRL C turns it off. CTRL N makes the computer stop at the bottom of each page, etc., etc. More information on control codes is given on page 378.
Another key useful in special circumstances - like word processing.
These keys can be somewhat confusing because they seem to generate the wrong characters sometimes. The problem is that there are two international standards for displayed characters (Teletext and ASCII) and the BBC Computer can display both. MODE 7 generates the Teletext display characters and MODES 0 to 6 show the ASCII characters. But don't worry, the computer recognises the key correctly regardless of what it has to display on the screen. For completeness, here is a table showing all these characters:
|On the key||Displayed on the screen in MODE 7||in MODES 0 to 6|
Note that in MODE 7 a zero is shown as a rather pointed 0 whereas in all other modes, zeros have a slash to help to differentiate them from the letter O. The keyboard is also marked in this way.
There may be a slot to the left of the main keyboard where it will be possible to insert cartridge packs containing games and other programs. This inexpensive option will enable users to play games and use other programs with the minimum of effort.