We receive many queries on various aspects of the BBC and Electron machines and to help you fathom the depths of your Acorn machine there will be a regular letters page starting from the next issue. So do not hesitate to write and we will try to help.

To start you on the right track, I deal with some of the most common and most frequently asked questions. Surely the most common problem posed concerns programs which will not load or cannot be saved. It is an all-too-frequent comment that the computer is faulty. Ninety-nine percent of all difficulties in that area prove to be a cassette recorder problem rather than one with the computer. If you are experiencing problems with LOADing or SAVEing programs, use the following checklist to determine the likely fault before rushing to your dealer suggesting a machine is faulty. You could save yourself a good deal of time:

1. Load both sides of the tape - a good manufacturer will supply a back-up copy.
2. Try loading another piece of software, preferably from another manufacturer.
3. If you get a loading error message at the same point every time, i.e., Block 05, there is almost certainly a corruption on tape.
4. If one of the cassettes loads, you have two options - the cassette you have is corrupted or badly recorded or your tape recorder is at fault. In most cases it is the tape recorder. Cassette recordings vary in quality and therefore a certain amount of variation occurs between software from different manufacturers. That is due to the equipment and quality of tape used. If your recorder has both volume and tone-pitch controls, try loading the tape at different levels until you are successful. Failing that, try to borrow a recorder from a friend to load the program. If it loads, your recorder is at fault.
5. SAVE your program at different volume and tone levels and then try to LOAD.
6. Don't be fooled by the fact that you can load commercial programs but are not able to save your own. That is not a fault with the computer but again a tape recorder problem. The comments about recording variations apply equally. In general, the most frequent difficulties occur with recorders which do not have both volume and tone controls but there are recorders which have pre-set levels and they work just as well.

Remember that tape recorders are delicate instruments and should be well-maintained. Clean the cassette recording heads regularly. Also check that your cassette lead is not broken.

Other points to look for include the addition of extra ROMs which might affect the running of some software. For BBC owners, check also that the tape is suitable for your machine - i.e., Model A, Model B, operating system.

The last point leads me to the next major source of confusion - which BBC have I? That is not as daft a question as it might seem. Since the BBC was introduced, there have been modifications to the system and the changes still perplex people. If you are now buying a BBC or have had one for a few months, the following probably will not apply, though it is useful to understand the differences.

If you buy a BBC computer today, it will be a Model B, Operating System 1.2 and Basic 2. What on earth does all that mean?

Originally the BBC was launched in two separate models, A and B. Model A was a cut-down version of the B and had only half the memory - 16K. Also lacking were the peripheral ports enabling one to link the BBC to printers, joysticks, modems and disc drives. Model A was designed so that it could be upgraded to a full Model B specification or in part to the specific needs of the user. That has meant there are BBCs which are neither A nor B.

Since last autumn, production of the Model A has ceased and only Model B has been manufactured. So far so good. The areas which have caused most confusion have been the operating systems and Basic 2. First, the OS. The original operating system of the BBC was OS 0.1 and its major disadvantage was a random fault preventing correct recording of the first block of saved information. OS 0.1 would not support paged ROMs; in other words the user could not use the sideways ROM sockets for extra utilities like word processors. Those bugs were cleared in the series 1 OS and it includes enhancement of the FX calls. There are very few machines around with the 0.1 OS and most original owners have upgraded their BBCs to the 1.2.

If you have bought a BBC second-hand and want to check what operating system it is, type *FX 0 (RETURN) and the machine will inform you of the OS number. Similarly you can determine the version of Basic by typing REPORT (RETURN) when the machine is first turned on. If the message is dated 1981 it is Basic 1 and if dated 1982, Basic 2.

To the majority of users the differences between the two versions will not be noticeable. Basic 2 is probably of major use to the programmer in assembler language, as four new operations have been added. Besides those changes minor corrections and improvements have been made to arithmetic functions for greater precision and to a few Basic keywords. The main changes for Basic programmers to note is the addition of two new commands, OPENUP and OSCLI.

OPENUP gives the same result as using OPENIN on Basic 1 but the meaning of OPENIN has changed in Basic 2. In Basic 1, it was not possible to open a file for read-only operations. That is now possible in Basic 2 using OPENIN. If that is not clear, refer to the user guide for explanation of file handling.

The other new keyword is OSCLI. It is a very useful command enabling the user to take a string expression and create an operating system command.

How close a relative to the BBC is the Electron? If you are one of the people who own an Electron you have probably been asking yourself, and your dealer, what BBC programs will run on your machine. First, let us look at the difference between the two computers.

The Electron is a cut-down version of the BBC, not merely in size but in its overall power. It has the same memory as the BBC B but lacks the peripheral ports. That has been catered for by an edge connector board at the rear which will attach to an expansion unit soon to be released by Acorn.

The language is BBC Basic 2 and is virtually the same. The difference is noticeable in the ENVELOPE command for SOUND, where only eight out of the 14 parameters are present. The printed circuit board is not the same and there is the noticeable absence of the 6845 CRTC and the 6522 VIA which enable the sideways scrolling and hardware timing for games such as Planetoid.

The functions of those chips are contained in the ULA but the versatility of programming those functions is not fully present. The Electron is slower than its BBC counterpart and that is one reason for rewriting programs. The other is Mode 7 or, to be more exact, the lack of Mode 7.

The Electron has all the screen display modes of the BBC except Mode 7. The Electron will default automatically to Mode 6 if it encounters a Mode 7 statement but that can still cause some very funny-looking displays. The following are points to consider when using a BBC program on the Electron.

As a general rule of thumb, most arcade games will not run on the Electron because of the probable use of the 6522 and 6845 in programming and the speed difference between the two machines. As those games are usually protected, it is unlikely you will be able to list and change a program. It is best to contact your dealer or the manufacturer and ask if an Electron version is being written.

Converting programs written on a BBC, say by a friend or at school, is a relatively easy task. The thing to look for is the use of *FX calls and Mode 7. The Electron will accept *FX calls it cannot implement like *TV commands but will do nothing with the command. I mentioned that there is a difference in speed between the two machines. To increase the speed on the Electron, try taking out or reducing any time delay loops if present on the BBC version; there are sometimes 'FOR-NEXT' loops or 'X =INKEY(40)' statements in a BBC program to slow the running of the program.

Mode 7 is the other major headache. Often the Mode 7 screen is used for presenting instructions or text and advantage is taken of using double-height characters by implementing a CHR$141 statement. The best thing to do is either to remove the CHR$ statements from the PRINT line or to re-write the text section in Mode 6.

In the next few issues I will look at ways of making your Acorn machine work for you, methods of programming and utilities for use in your programs. Keep the letters rolling, whatever the software problem, or even if you just want to pass on your tips to other readers.