TheDesktop Development Environment manual is the essential documentation to make the most of the Desktop Development Environment. Both have been adopted and are now updated by RISC OS Open. The manuals come free with the DDE and are also available to buy in printed manual form.
The first edition of the manuals was produced in 1994 and it has been revised several times. As you would expect from professional developers, RISC OS Open includes a changelog so you can see what exact changes have been made. Last major update was in 2015. The manuals have also been rebranded with the RISC OS Open cog logo and company name.
There are 3 manuals in the set.
The Desktop Tools manual (329 pages) covers all the tools in the DDE (Make, Squeeze, SrcEdit, ABC, etc). There is a nice introductory section at the start telling you how to setup and start using the tools.
There are lots of screenshots to show the features in action. It should not be regarded as a tutorial but there is lots of material on using them. The Desktop Debugging tool includes 60 pages explaining how to use it.
The last 100 pages are Appendices which cover a summary of changes added over the years and information which you would need to use the tools (Library file formats, alignment details, file syntax,etc).
The Acorn Assembler manual (159 pages) shows you how to use ObjAsm. It includes some details on ARM Assembler instructions but it is not a tutorial (it does include some good further reading suggestions for you to learn ARM code). The focus is on using the tool and its features (ie labels, macros compilation). There are also some short chapters on writing RISC OS modules and interacting with C.
The Acorn C/C++ manual (438 pages) provides provides detailed coverage of the C and C++ language features supported by the Compiler (as well as the libraries) and some useful details and tips on writing RISC OS applications from C or C++. The languages are cleanly separated out so you only want to write C, it is easy to skip the non-relevent items. Again it is not a tutorial on coding, but a detailed summary of all the details you need to develop code.
All three manuals include an index at the back to help you to navigate as well as very detailed section descriptions at the start and a clear structure.
All three books are part of the DDE or available in a printed version (discounts for registered developers). The printed package makes a fairly bulky doorstop (and a great table stand for my MacBookPro!). I also find that it is the sort of programming content which I like to read and reread offscreen.
Further details on the DeskTop Tools Manual can be purchased from RISC OS Open website or they usually have some copies as Show events. Maybe something to check out at the South West Show later this month.
If you are looking to write software, you should also consider the Style Guide which tells you how the software should look and act to fit into RISC OS nicely.