vim: How do I map number keys? [duplicate]

Question

Not sure why this isn't working, but I can't map Ctrl+NUMBER to a command in vim.

For example this works:

nnoremap <C-r> :bufdo bdelete<cr> 

This doesn't:

nnoremap <C-8> :bufdo bdelete<cr> 

Do I have to do something special in order to map number keys?

gvim 7.4, Windows 7

Answer 1

This does not appear to be possible for reasons of portability.