Hitting the Books: The programming trick that gave us DOOM multiplayer

engadget.com:

Since its release in 1993, id Software's DOOM franchise has become one of modern gaming's most easily recognizable IPs. The series has sold more than 10 million copies to date and spawned myriad RPG spinoffs, film adaptations and even a couple tabletop board games. But the first game's debut turned out to be a close thing, id Software cofounder John Romero describes in an excerpt from his new book DOOM GUY: Life in First Person. With a mere month before DOOM was scheduled for release in December 1993, the iD team found itself still polishing and tweaking lead programmer John Carmack's novel peer-to-peer multiplayer architecture, ironing out level designs — at a time when the studio's programmers were also its QA team — and introducing everybody's favorite killer synonym to the gamer lexicon. 

Excerpted from DOOM GUY: Life in First Person by John Romero. Copyright © 2023 by John Romero. Published and reprinted by permission of Abrams Press, an imprint of ABRAMS. All rights reserved.

In early October, we were getting close to wrapping up the game, so progress quickened. On October 4, 1993, we issued the DOOM beta press release version, a build of the game we distributed externally to journalists and video game reviewers to allow them to try the game before its release. Concerned about security and leaks, we coded the beta to stop running on DOS systems after October 31, 1993. We still had useless pickups in the game, like the demonic daggers, demon chests, and other unholy items. I decided to get rid of those things because they made no sense to the core of the game and they rewarded the player with a score, which was a holdover from Wolfenstein 3-D. I removed the concept of having lives for the same reason. It was enough to