This blog is updated daily.
A general description is here.
The 32-bit and 64-bit builds are now treated equally, as it is anticipated that 64-bit R will soon be (if not already) the more commonly used. This entails:
The ‘Rterm’ or ‘Rgui’ title mentions 32-bit as well as 64-bit.
The desktop icons are labelled ‘R i386’ and ‘R x64’.
‘R CMD INSTALL’ for a package with compiled code will fail if compilation fails for any of the installed sub-architectures: use ‘--no-multiarch’ to override this.
‘postscript(file = "|cmd")’ now works on Windows.
‘file.symlink()’ is now implemented on NTFS file systems on Vista or later, for accounts which have suitable permissions (and most will not). It can link existing directories, and existing-or-not files.
The behaviour of ‘unlink()’ for reparse points (including junctions and symbolic links) has changed. It no longer follow links (deleting the contents of the link target rather than the link), and it is able to delete the link itself (given sufficient permissions).
There is a new function ‘Sys.junction()’ to create junction points on NTFS file systems.
C-level error formats now use the trio library, and so for example use ‘1.53e-11’ (as required by C99) rather than ‘1.53e-011’.
The installer has many fewer options with more files always being installed, as file space is nowadays no longer an issue.
It is now possible to select ‘64-bit Files’ from the standard installer even on a 32-bit version of Windows.
As the current toolchain uses only 32-bit executables, it is possible to compile a package for both architectures on 32-bit Windows provided both architectures of R have been installed: use ‘R CMD INSTALL --compile-both’.