Text editor with split screen option

vim can easily do that:

ctrl+ws - Split windows

ctrl+ww - switch between windows

ctrl+wq - Quit a window

ctrl+wv - Split windows vertically

:sp filename

will open filename in new buffer and split a window.

You can also do

vim -o file1 file2

To open the files in a split screen layout. Replace -o with -O for vertical split instead of horizontal.

This can be done using Emacs. It works in GUI and in terminal mode. You can even split multiple times. Here are some basic key combinations:

C-x 2 Split the selected window into two windows, one above the other (split-window-below).
C-x 3 Split the selected window into two windows, positioned side by side (split-window-right).
C-Mouse-2 In the mode line of a window, split that window.

Source: http://www.gnu.org/software/emacs/manual/html_node/emacs/Split-Window.html

With vim, you can use split or vsplit.

The first one will split horizintally and the second one will split vertically.

CTRLw then to navigate through split screens.

You can also use tab. tabnew filename will open filename in a new tab. You can use tabnext and :tabprevious to navigate between tabs.

I personnaly maps the left and right arrows to navigate between tabs:

map <right> :tabnext<CR>
map <left> :tabprevious<CR>
inoremap <right> <ESC>:tabnext<CR>a
inoremap <left> <ESC>:tabprevious<CR>a