The RISC OS Programmer's Reference Manual

David Spencer previews Acorn's definitive reference guide to RISC OS.

Acorn has just released the final draft of the RISC OS Programmer's Reference Manual. The pre-release version we have has inconsistent page numbering and a lack of full indexes, but apart from that is identical to the final version which will be on sale shortly.

The new PRM is a massive four volumes, each one being around 500 pages in length. This makes it over three times as long as the existing PRM. Rather than repeating the indexes four times, these have been separated into their own volume. As well as a conventional subject index, there are also indexes for star commands, OS Byte and OS Word calls, and SWIs (both by number and name).

CONTENT

The manual is split into five major sections, plus a set of appendices and tables. The first section is referred to as an introduction, but is in fact much more than that. It is in this section that all the fundamentals of RISC OS are explained, including the basis of SWI calls, star commands, OS Byte and OS Word, interrupts, events, errors, buffers and vectors. Also in this section is a brief description of the Archimedes hardware.

The second section covers the RISC OS kernel which consists of all the central features that are not dealt with separately. Among these are the VDU drivers, character input and output, relocatable modules and memory management.

The third section is devoted entirely to the subject of filing systems. This handles the individual filing systems as well as the FileSwitch and FileCore modules which are central to all filing systems. The fourth section explains in detail the Window Manager, and therefore also includes the material relating to the writing of multi-tasking applications. The final section is entitled 'System Extensions', and deals with all the leftovers. For example, the Font Manager and sound system feature here.

The appendices cover ARM assembler, the linker, file formats, and various topics related to interfacing with compiled languages. The manual is rounded off with tables of VDU codes, screen modes, file types and character sets.

Obviously with a manual that is three times the length of the existing PRM, you would expect it to contain much more material, and this is indeed the case. Much of this is totally new information that arises as a result of the new features of RISC OS. On the other hand, though, many areas which are largely unchanged from Arthur are now documented in greater detail, including sections on some previously uncovered subjects. For example, there is now a large chapter on Expansion Cards (Podules) which explains the basis of writing a podule as well as detailing the available commands. The existing PRM has just two pages on the subject.

Another idiosyncrasy of the new PRM is the chapter on the Font Manager. Rather than documenting the Font Manager supplied with RISC OS, it instead deals with the new Outline Font Manager which is currently only available with the Acorn DTP package.

STYLE AND PRESENTATION

The new PRM is in the standard 2/3rd A4 size adopted by Acorn, and each page has a line down the left margin, with sub-headings in the margin. This layout is very similar to that of the other RISC OS guides. The material content, and its layout, has been rationalised when compared with the original PRM. Each major section is split into a number of chapters, each of which covers an individual topic (for example character output or relocatable modules).

Each chapter starts off with an introduction which lists what is covered in that chapter, followed by an overview which explains the principles of the particular RISC OS feature dealt with by that chapter. Next is a section of 'technical details', which covers the material in more detail. This is followed by the explanations of star commands, SWI calls etc, with an uncluttered one per page layout. Some chapters also contain application notes to explain particular methods and techniques.

One thing which I'm sure many people will find a little strange is that the new PRM is for RISC OS, while the old one was specifically for the Archimedes. This means that throughout the manual an abstract RISC OS based computer is referred to, rather than the Archimedes. Presumably this is so that the material is also of relevance to the R140 UNIX workstation.

CONCLUSION

The RISC OS PRM is one of those books that if you need it, you have to buy. There are no alternatives, and hence you have to live with any failings. Thankfully, though, I can say that there are few of these, and the PRM is a great improvement on the original, both in terms of content and presentation. However, it must be remembered that this is a reference work, and many people will find it hard going.

I am sure that many people who have already bought the existing PRM are going to begrudge having to pay for another manual, especially when it will cost more than the actual RISC OS upgrade. All I can say is that this is the cost of progress, and if you want to use the new features of RISC OS then you will have to buy the new PRM. If you are not convinced, then you might like to consider that a similar set of manuals for the £400 Atari ST will set you back around £200.

People who have not already bought the existing PRM must decide whether they have a need for such a manual. As it stands, the Welcome Guide and User Guide supplied with RISC OS are very much aimed at the user rather than the programmer. Even the optional BBC Basic Guide only covers the Basic language, and not the operating system features. Therefore, if you want to do any serious programming (and by that I mean anything more than a few lines of Basic), then the RISC OS Programmer's Reference Manual is a must.

The RISC OS Programmer's Reference Manual is due to be launched in the autumn at a price of around £79.00.