syntax « open « C File Q&A

1. VIM: Certain .c files opening without syntax highlighting    stackoverflow.com

I have some .c files that don't automatically highlight in vim. This problem only recently started. I have not edited my .vimrc file:

set number
nnoremap <F2> :set nonumber!<CR>:set foldcolumn=0<CR>
set ignorecase
syntax on
filetype plugin ...

2. syntax to open a *.txt file    forums.devshed.com