Window systems for textual user interfaces exist. Windowing systems are not
confined to graphical user interfaces.
This is a screenshot of Borland's Turbo Pascal, showing the Turbo Vision
interface in action. Observe that Borland chose to put brackets around a
window frames' widgets, and indicated hotkeys in menus with colour. The
active window was indicated with brighter frame colours, and window titles
only occupied as much of the top of the frame as they required.
This is a screenshot of Microsoft's Visual Basic for DOS, showing Microsoft's
TUI windowing interface in action. Microsoft used box-drawing characters
for widgets, and denoted the active window by a change in its title, which
also encompassed the whole of the top of the frame.
Perhaps the most well-known such TUI window system is Borland's Turbo Vision
for DOS, which was used in several of Borland's own DOS products. Other
systems include the one that was used by Microsoft's Visual Basic for DOS,
and several other Microsoft products for DOS, including Works and the Exchange
Client. Unlike Borland, Microsoft never made its TUI window system public.
In the early 1990s, there were many programming libraries for various
programming languages, including C++ and Pascal, implemented for IBM-compatible
PCs running MS/PC/DR-DOS, that would display such systems. Their major problem
was that the systems were not independently available, and had to be hard-wired
directly into the applications themselves. Thus there were both variations
in look-and-feel between different TUI applications, and no common UI
communications facilities between such applications (such as global clipboard,
for example).
These libraries varied in capabilities from simple box-drawing and
output-clipping routines to full windowing systems — such as Turbo
Vision. Their common features were the use of the box-drawing characters in
the (text mode) PC character sets, and a general adherence to IBM's Common
User Access guidelines for UIs (such as the [F1] key being a
"help" key, for example).
Turbo Vision and its ilk actually provide full TUI windowing systems, with
multiple overlapping windows, which "cast shadows" on windows lower in the
Z-order. Both Turbo Vision and Microsoft's TUI window system both employ(ed)
a menu bar across the top of the screen, Macintosh-style, rather than across
the tops of individual windows, which responded to [Alt] key
combinations, revealing drop-down menus.
Similarly, in both Borland's and Microsoft's systems windows are drawn with
single-line or double-line box drawing characters, and sport titles and
widgets for resizing, scrolling, closing, maximizing, and minimizing. Child
windows include labels, checkboxes, radio buttons, entryfields, listboxes,
scrollbars, buttons, and comboboxes.
Turbo Vision came with Borland C++ for DOS, which included a full printed
programming manual and library reference. Turbo Vision was a C++ class
library, but was also available in Borland Pascal. Full source code was
provided to people who had bought Borland C++. Eventually, Borland donated
the source code for Turbo Vision to the public domain.
Various ports of Turbo Vision exist. However, the main problem with porting
the library is that DOS Think assumptions are endemic within it. Porting even
to OS/2, which at least supports some of the same basic keyboard/mouse/screen
API concepts as DOS (albeit accessible directly via a high-level language API
rather than via assembly language), is quite difficult. DOS Think assumptions
that were hardwired into Turbo Vision included direct access to video RAM,
polling for keyboard/mouse I/O, and the assumption of a single-tasking
operating system and a single-threaded program. (OS/2 was multi-threaded
right from version 1.0, in 1987.)
These TUI window systems are sometimes known as Character-Oriented Window
Systems, although that's somewhat of a misnomer. GUI window systems display
characters, too. The defining characteristic of these window systems is that
they address the display as if it were an array of character cell and
attribute pairs — e.g. the PC-compatible VGA/EGA/CGA display adapter in
text mode.
