Experimental binary build of R and packages for Windows (UCRT, 64-bit, using
an experimental toolchain), only intended for testing, not for production
use.

R-devel-win.exe is the installer (R was patched by r_gcc9_ucrt2_2.diff and
installs binary packages included here).

demo/CRAN/patches
  patches of some CRAN packages so that they can be built with the
  experimental toolchain

demo/CRAN/bin/windows/contrib/4.1
  binary builds of the patched CRAN packages

demo/CRAN/out
  outputs of R CMD check for each package

demo/BIOC/bin/windows/contrib/4.1
  binary builds of BIOC packages, only those needed by CRAN packages, unpatched

demo/BIOC/out
  outputs of R CMD check for each package


Please see https://svn.r-project.org/R-dev-web/trunk/WindowsBuilds/winutf8/winutf8.html
for more details.