Using the Acorn C/C++ Development Environment to write 32-bit RISC OS

Acorn released in 1994. It includes new 32-bit versions of the C compiler, ARM assembler, linker and all of the other tools that were in the original C/C++ pack. More importantly it enables software to be ported to Castle’s new 32-bit IYONIX PC ahead of its launch. Acorn C/C++ cost £250 in 1994 and was supplied with four printed manuals totalling nearly 1400 pages and several floppy discs. Castle supply a single CD for £99 which contains the new software, the updated manuals in PDF format, and some useful public domain software including StrongEd, Zap, Perl and 32-bit IYONIX versions of Colin Granville’s PDF reader and FTPc for transferring files to or from FTP sites. All of these are installed automatically by the supplied installer and work with RISC OS 3.10 onwards. As if that wasn’t enough Castle is now including a new version of the ABC Compiler which was previously available from Pineapple Software and SID, an ARM disassembler and analysis tool. 1. 32-bit Mode When Acorn designed the ARM processor back in the mid-80’s it was widely regarded as an innovative and elegant design. One key feature was to combine the Program Counter (PC) with the Processor Status Register (PSR) into a single 32-bit register. This had the benefit that the PSR could be saved automatically with the PC to achieve fast subroutine calls and quick interrupt response. The disadvantage was that ‘26-bi