I have a couple of new items of PD software to report again this issue, both of which are of very high quality. I keep thinking that there must be an end to the new software which keeps appearing, especially as the circle of Beeb programmers shrinks, but these gems just seem to keep appearing.

ADDOS is the name given to a modified version of Acorn's own 1770 Disc Filing System (DFS) which has been produced (by modifying the original Acorn product) by Andrew Donald. The DOS part of the name (I suspect) comes from the Disc Operating System (DOS) used on PC type computers, but the AD part is more obvious.

The original Acorn DFS was designed around a disc controller chip called the 8271, which worked in single density disc formats only. When Acorn introduced the Master series, it took the opportunity to change to using a 1770 disc controller chip, which is capable of double density operations as well as single density.

Single density and double density, for those who are unfamiliar with these terms, are basically two different ways of recording the magnetic data on a disc surface. Fairly obviously from the names, double density recording fits more data onto a disc than single density, but the name is nevertheless a little misleading - you don't get twice as much data on a double density disc, more like 1.6 times the amount available in single density mode. This meant that the DFS had to be rewritten to work with the new chip, resulting in the Acrn 1770 DFS. This DFS worked just like the original (8271) DFS, in that it worked in single density only. Double density disc recording was left for the ADFS ROM, but other software suppliers took the opportunity to introduce double density DFS systems.

These never achieved very widespread use because there was no guarantee that someone you might send a disc to could use double density DFS discs. Andrew Donald saw the potential benefits of having a double density DFS and, rather than simply buying a non-Acorn alternative, set to work on Acorn's own 1770 DFS. He very cleverly succeeded in modifying it to work in double density rather than single density, and has managed to persuade Acorn to allow him to distribute the resulting ROM image via the public domain. He kindly sent me a copy of the ROM image, which I have tried out on a Master 128 and have found it to work fine.

Andrew has included a short text file with the ROM image which gives a few pointers on the use of the new double-density DFS, but has also written an article giving more details, including a description of how he made the conversion work. The article will be published in a magazine for Beeb enthusiasts called ByteBack.

ByteBack is a newish A5 format magazine for BBC users and enthusiasts, run by Paul Harvey and produced roughly once a month. It costs £1.00 per copy and is available from 33 King Henry's Mews, Enfield Lock, Middlesex EN3 6JS, should you wish to get in touch to find out more about ADDOS.

ByteBack is in some ways similar to early issues of Beebug in that it includes hints and tips for beginners as well as more advanced material, and general discussion articles (in relation to the subject matter of this column it also includes a PD software reviews section, so it isn't entirely out of context here).

The second new program which I have to report on this issue is the latest from David Harper, whose name should be familiar to regular readers. David has this time come up with a program for the 6502 side of a Master (or Model B), rather than the Master 512 co-processor for which he has been very prolific in the past. This program, a sideways printing utility, is up to his usual high standard and is very professionally presented.

The Sideways Printer is a program which allows text to be output "sideways" on a dot-matrix printer. In other words, text is printed in "landscape" format (rather than the usual "portrait" format), and is thus rotated by 90 degrees from the way it normally appears.

To use the program you need a 24-pin (or 48-pin) Epson-compatible dot matrix printer and a BBC Model B with OS Version 1.20, Model B+ or Master having at least one free bank of sideways RAM.

Apart from a couple of star commands to turn it on and off, the Sideways Printer is totally transparent to the user and to the system. This means it can be used with any word processor, or indeed with any other program (such as a spreadsheet) which outputs text to the printer. It is fully Tube compatible, and even works well on the Master 512.

The Sideways Printer can only be used for text output. It will not cope with pictures, diagrams, etc. which are output in dot graphics mode. To use it you must first load the ROM image file into a bank of sideways RAM. On the Master or B+128 you do this with a command such as:

*SRLOAD SIDEPRT 8000 [n]

where [n] is the number of the sideways RAM bank you wish to use. You then need to initialize the program. Some versions of the Operating System (on the Compact and later versions of the Master 128) allow you to do this as you load by adding an "I" to the end of the *SRLOAD command. Otherwise, the approved way is to press Ctrl-Break (in fact, you can also initialize the program by writing the value &82 to memory location &2Al+[n], where [n] is again the number of the sideways RAM bank).

Note that this program must be run in sideways RAM. It will not work if you blow it into an EPROM. Some versions of sideways RAM sold for the Model B are designed to "look like" ROM. The Sideways Printer will not work with one of these.

For the sake of compatibility, the Sideways Printer has been designed to respond to the same sequences as an Epson printer normally does. Thus, for example, sending to the printer the two ASCII characters 27,52 (ESC,"4") starts printing in italics, whether the Sideways Printer is on or off. Most word processors have their own method of issuing control sequences to the printer, of course.

There are limitations, and the most severe one is that all sideways output occurs at 12 characters per inch (apart from doubling the character width). A number of printer effects have been implemented, however. The ones that work include bold, italics, underline, double-width and double-height characters, as well as various line spacings.

Next issue, I promise that I will give some information about sources of PD software. This has been promised for a couple of issues now, but I am still checking which libraries and user groups are still active. If you run one or other such source of PD, please let me know as soon as possible so that I can make the information as complete as possible. As usual, my address is 18 Carlton Close, Blackrod, Bolton BL6 5DL.