The DJGPP environment, utilizing GCC
|Stable release||2.0.3p2 / June 10, 2002|
|Operating system||DOS and Windows|
DJGPP (DJ's GNU Programming Platform) is a development suite for 386-based IBM PC compatibles which supports DOS-compatible operating systems. It is guided by DJ Delorie, who began the project in 1989. It is a port of the popular GCC compiler, as well as mostly GNU utilities such as Bash, find, tar, ls, Gawk, sed, and ld to DPMI. Languages available include C, C++, Objective-C/C++, Ada, Fortran, and Pascal.
The compiler generates 32-bit code, which runs natively in 32-bit protected mode while switching back to 16-bit DOS calls for basic OS support. However, unlike Open Watcom, it is not a zero-based flat model due to preferring NULL pointer protection for better stability. It is currently based upon a variant of the COFF format. It can access up to 4 GB of RAM in pure DOS when using a suitable DPMI host (e.g. CWSDPMI r7 or HDPMI32).
DJGPP presents the programmer an interface which is compatible with the ANSI C and C99 standards, unofficial DOS standards, and an older POSIX Unix standard. Compiled binaries are long file name-aware and handle such filenames under Win32 by default. TSRs to support LFNs under plain DOS or Windows NT 4 are available.
While DJGPP runs in 32-bit protected mode, its stub and library heavily rely upon many 16-bit DOS and BIOS calls. Because the x86-64 versions of Windows lack support for 16-bit programs, there is no NTVDM, and DJGPP applications cannot be run. Under x86-64 systems these applications function only through emulation (e.g. DOSBox), virtualization (e.g. VirtualBox), or similar (e.g. Linux's DOSEMU). This problem arises because in long mode x86-64 processors do not support the virtual 8086 mode used to run 16-bit code in IA-32 processors. Newer x86 CPUs with VT-x do support paged real mode and unrestricted guest mode execution.