BigVGA is a library and a command-line tool to set high-resolution text modes in FreeDOS and other DOS-compatible systems.

WARNING: this is still at the work-in-progres proof-of-concept stage but basic functionality should already work in QEMU. Try e.g. bigvga.exe 136x43 to set a text mode with 136 columns and 43 lines (and approximate 16:9 aspect ratio) in QEMU. Revert to a normal 80x25 text mode by running the DOS command mode co80 or rebooting your system.

Unlike other projects that rely on SuperVGA hardware, BigVGA only uses basic VGA features.

The main target is emulators (e.g. qemu, dosbox, dosemu, bochs...) but it might also work on some laptops or LCD screens.

If after running BigVGA you want to go back to a safe screen state, optionally press CTRL-C to make sure you are at the DOS prompt and then type "mode co80" (without the quotes) and press Enter. You can type this command even blindly if you don't see the output if the screen is unreadable.

If that doesn't help, simply reboot your emulator or OS: BigVGA doesn't make any permanent change, all changes are reverted at system reboot.

QEMU by default resizes its window in response to screen resize requests from BigVGA, however if you manually change the QEMU window size all subsequent requests from BigVGA will only change the state inside the emulator and QEMU will scale the text to fit into the window size that you previously set. A downside of this scaling is that text will appear blurry. To switch back the QEMU window to the "native" unscaled dimensions press CTRL-ALT-U.

BigVGA is free software, released under the MIT License. See the LICENSE file for details.

The latest version of BigVGA is available at: https://github.com/LinoMastro/bigvga

BigVGA should be compatible with a wide range of DOS compilers and DOS-compatible operating systems, including FreeDOS.

It should compile correctly and without warnings in gcc-ia16 (with the i86 library), Open Watcom, DJGPP, Borland Turbo C, Microsoft Quick C and Bruce C compiler (bcc, with the -ansi flag).

BigVGA text modes are identical to the standard BIOS text mode 3 (e.g. same video memory location at segment 0xB800) except that they have a different number of columns and/or lines than the usual 80x25.

Most commandline utilities should work fine with non-standard text screen sizes but fullscreen TUI programs are a bit hit-and-miss. For example the FreeDOS edit 0.9a program accepts any number of columns but expects the number of lines to be 25, 43 or 50. The vi.exe editor part of Open Watcom instead works in any BigVGA mode.

Generally any program that outputs text via BIOS or DOS syscalls should work correctly and even programs that directly access the video memory should be compatible with BigVGA text modes provided that they don't hardcode the number of columns and lines to be 80x25 and instead read the actual values from the BIOS Data Area and/or from a BIOS Int 10/AH=0Fh call.

Low-level programs like mouse drivers and NANSI.SYS should also be fully compatible with BigVGA text modes.

So far most testing has been done in QEMU, compatibility with more emulators and potentially even some real hardware will improve as BigVGA evolves. Most emulated VGA adapters should work, BigVGA doesn't require a SuperVGA card.

Dual-graphics-card dual-screen DOS systems (e.g. with a VGA and a MDA adapter) should be compatible. Make sure that the active card is the VGA one before running BigVGA.

Since BigVGA modes use a very low refresh rate they will likely never be compatible with real CRT screens over a VGA connector.

The FreeDOS mode command can also change text mode resolution (e.g. mode con cols=80 lines=28) however it only uses standard BIOS calls and is limited to a few available modes. On VGA adapters the "mode" command never exceeds a resolution of 720x400 pixels for maximum hardware compatibility, so for example the 80x50 mode is achieved by using a small 9x8 font, while BigVGA uses the standard VGA 9x16 font and for the same 80x50 mode offers a much bigger screen size in emulators.

The wtm (Windowed Text Mode) program by Jason Hood works in a very similar way to BigVGA but provides more limited hardware and emulator compatibility. It's available at: http://adoxa.altervista.org/tm/

The SVGATextMode program for Linux and DOS has similar goals but requires a supported SVGA adapter to go beyond the usual VGA text modes: http://freshmeat.sourceforge.net/projects/svgatextmode

Bug reports, feature requests and PRs are welcome via the BigVGA GitHub page: https://github.com/LinoMastro/bigvga

Detailed information about standard VGA registers can be found at http://www.o3one.org/hwdocs/vga/vga_app.html and from the FreeVGA project page http://www.osdever.net/FreeVGA/home.htm and specifically for the CRT registers at http://www.osdever.net/FreeVGA/vga/crtcreg.htm

The preferred style and indentation is the one generated by the following GNU indent command:

indent -gnu -br -ce -brs -ncs -di4 -i4 -npcs -nut -cli4 -c1 -T FILE *.c *.h