Do I need to manually set $VIMRUNTIME on my pc

Question

For me I think the following is the case:

$VIMRUNTIME='C:/Program Files (x86)/Vim/vim73'

But if I look in the pc's environment variables (via Computer>Properties etc) I cannot see this path - should I add it manually?

_vimrc currently looks like the following:

set nocompatible
source $VIMRUNTIME/vimrc_example.vim
source $VIMRUNTIME/mswin.vim
behave mswin

set diffexpr=MyDiff()

" Use CTRL-S for saving, also in Insert mode
:nnoremap <C-S>     :<C-U>update<CR>
:vnoremap <C-S>     :<C-U>update<CR>gv
:cnoremap <C-S>     <C-C>:update<CR>
:inoremap <C-S>     <C-O>:update<CR>

function MyDiff()
  let opt = '-a --binary '
  if &diffopt =~ 'icase' | let opt = opt . '-i ' | endif
  if &diffopt =~ 'iwhite' | let opt = opt . '-b ' | endif
  let arg1 = v:fname_in
  if arg1 =~ ' ' | let arg1 = '"' . arg1 . '"' | endif
  let arg2 = v:fname_new
  if arg2 =~ ' ' | let arg2 = '"' . arg2 . '"' | endif
  let arg3 = v:fname_out
  if arg3 =~ ' ' | let arg3 = '"' . arg3 . '"' | endif
  let eq = ''
  if $VIMRUNTIME =~ ' '
    if &sh =~ '\<cmd'
      let cmd = '""' . $VIMRUNTIME . '\diff"'
      let eq = '"'
    else
      let cmd = substitute($VIMRUNTIME, ' ', '" ', '') . '\diff"'
    endif
  else
    let cmd = $VIMRUNTIME . '\diff'
  endif
  silent execute '!' . cmd . ' ' . opt . arg1 . ' ' . arg2 . ' > ' . arg3 . eq
endfunction

Answer 1

No. $VIMRUNTIME is a special environment variable that automatically gets set by Vim.

:help $VIMRUNTIME would have already told you this:

You don't normally set $VIMRUNTIME yourself, but let Vim figure it out.

Learn how the excellent and comprehensive :help is structured; all the information is in there (you just need to know how to find it)!