You are about to visit DOSBox DOS Emulator
"DOSBox, an x86 emulator with DOS"
DOSBox can be classified as an emulator software, which, as can be gleaned from the name and its classification, emulates the experience of MS-DOS using an IBM PC-compatible computer (meaning no Mac OS X computers); the entire experience is emulated, including graphics and sound cards that worked for older computers. This means that applications, specifically older games, can run on an environment correctly and properly as they had been meant to be played, since when they run on newer PCs with newer standards and hardware (not to mention newer operating systems) they won't work as well as they did on the hardware and OS they were originally written for. DOSBox has received numerous accolades from the industry and has been deployed commercially by game developers and publishers, such as Activision Blizzard, Bethesda Softworks (for their earlier Elder Scrolls games), LucasArts, and Id Software (for their Wolfenstein re-releases). DOSBox is free and open-source, written in C++ and distributed under the GNU General Public License (GPL).
There are some 21st century features to DOSBox, though, such as virtual hard drives, P2P (peer-to-peer networking), and image and video capture capabilities similar to Fraps. Though only working initially for Microsoft Windows, there have been numerous community-driven ports of the software, for instance to Mac OS X and Linux.