CP/M is an operating system which was optionally used on a number of computers during the 1980s, including the Coleco Adam, IBM-compatibles, and some Atari models. While it is most authentic to utilize one of these computers for using this operating system and the software programs which run under it, free CP/M emulator software is available for using it on more recent computers...

ZRP/M: An open-source emulator for CP/M 2.2, ZRP/M can be used on IBM-compatible systems. The total download size is about 647k. Several different files must be downloaded separately to use this software, which is available for free here:

http://www.retroarchive.org/cpm/archive/unofficial/zrpm.html

SPASM: This is a set of CP/M software programs accompanied by a free emulator, which will run in Windows or DOS. It is available for download (very quick) on this page, along with a few other free and shareware CP/M emulators:

http://www.cpm.z80.de/emulate.html

MyZ80: In addition to emulating the Z80 processor (found in some computers from the '70s and '80s, like the Timex/Sinclair 1000 and early TRS-80 systems), MyZ80 may also be used to emulate the CP/M operating system and software. It is free for "educational purposes", or can be registered for thirty dollars. The MyZ80 emulator software is available for free download at the following web page:

http://ftp.gaby.de/pub/cpm/znode51/specials/myz80.htm

Apparently MyZ80 works in Windows XP and DOS, but not Vista. More information and screenshots can be found here:

http://www.z80.eu/myz80cpm.html

CP/M Emulator 1.01: This is a free, open-source emulator program for Macintosh computers. However, the documentation appears to be in Japanese. The zipped download file is just over 120k in size. It may be downloaded at the following URL:

http://homepage3.nifty.com/bugbug/cpm/

Please note that I have tested these emulator downloads with AVG anti-virus software, but have not confirmed that all of them are definitely safe to utilize; always be sure to use caution when downloading files or programs online.

Have a look at the following video to see someone's computer (looks to be from the 1970s) booting to CP/M and running the vintage text adventure software "Zork." If you are familiar with MS-DOS, you will notice the apparent similarity: