DOS was an single user 16-bit Operating System for PCs and compatible personal computers. It was developed at the end of the 1970s and is now obsolete as it has been almost completely replaced by Microsoft Windows.
Tomb Raider I was written for DOS 5.0 and above. It uses a 32-bit DOS Extender and can thus be started only on systems featuring a 32 bit chip - a fast Pentium (or equivalent) system is recommended. It also works with Windows in Real Mode DOS (95 to ME) and Glidos or DosBox (2000 and above). For more information see PC.
The version of DOS mostly used was provided by Microsoft. The newest stand alone version MS-DOS provided by Microsoft was 6.22, created in 1994. There are newer versions that were provided with Windows 95 (MS-DOS 7.0/7.1), 98 (MS-DOS 7.1), and ME (MS-DOS 8.0). Some of these versions can be used without the accompanying Windows.
When Microsoft moved to the NT line of operating systems, MS-DOS became more or less irrelevant. Compatibility with older programmes was insured by the inclusion of a command shell, providing a (more or less) MS-DOS compatible environment. With the rise of modern 64-bit X86 processors - introduced by AMD in the early 2000s and widely adopted since the 2010s - that are incapable of running 16-bit code in 64-bit mode the command shell is no longer capable of running DOS programs, thus DosBox is needed.
Besides Microsoft there were several other companies creating DOS systems that were mostly compatible with MS-DOS, like Digital Research (DR-DOS), Caldera (Open DOS), or Novell (Novell-DOS), among others.
Development of all these versions has been abandoned in the late 1990s and early 2000s and are considered mostly obsolete by now.
The only DOS operating system still in active development is FreeDOS, an open source implementation. First conceived in 1994 version 1.0 was released in 2006. The current version 1.2 was released in 2016. It is available free of charge and is sometimes used by PC manufacturers as a pre-installed OS when a Windows license would be to expensive and the end user plans to install his or her own system. FreeDOS can be downloaded as boot disks or bundled in a distribution together with many open source tools, making it the most sophisticated out of the box DOS system.
FreeDOS should run the original 1996 Tomb Raider without problems.
- http://www.freedos.org/download/ FreeDOS download page