HISTORY OF MASSIVELY MULTIPLAYER ONLINE GAMES

In 1973, Mazewar introduced the first graphic virtual world, providing a first-person perspective view of a maze in which players roamed around shooting at each other. This could be seen as a key progenitor not only of MMOGs but also of First Person Shooters. It was also the first networked game, in which players at different computers could visually interact in a virtual space. The initial implementation was over a serial cable, but when one of the authors began attending MIT in 1974, the game was enhanced so that it could be played across the ARPAnet, forerunner of the modern Internet.
You haven't lived until you've died in MUD. -- The MUD1 Slogan. Adventure, created in 1975 by Will Crowther on a DEC PDP-10 computer, was the first widely used adventure game. The game was significantly expanded in 1976 by Don Woods. Adventure contained many D&D features and references, including a computer controlled dungeon master.[1][2]
Inspired by Adventure, a group of students at MIT, wrote a game called Zork in the summer of 1977 for the PDP-10 minicomputer which became quite popular on the ARPANET. Zork was ported under the name Dungeon to FORTRAN by a programmer working at DEC in 1978.[3]
In 1978 Roy Trubshaw, a student at Essex University in the UK, started working on a multi-user adventure game in the MACRO-10 assembly language for a DEC PDP-10. He named the game MUD (Multi-User Dungeon), in tribute to the Dungeon variant of Zork, which Trubshaw had greatly enjoyed playing.[4][5] Trubshaw converted MUD to BCPL (the predecessor of C), before handing over development to Richard Bartle, a fellow student at Essex University, in 1980.