In the original Bomberman for the NES, passwords are called secret codes (シークレットコード shīkurettokōdo). Each code consists of 20 characters. Each character can be any letter in the Roman alphabet from A to P. This secret code system was lifted from Hudson Soft's earlier port of Lode Runner. However, because the system's error checking is not perfect, incorrect codes can be entered, leading to a number of glitched stages that greatly exceed the intended 50 stages in the game.
Bomber Boy retained this system, expanding the character set to all letters from A to Z as well as numerals 1 through 8, placing the letters in a grid instead of forcing the player to cycle through them one at a time, and providing arrow buttons to move forward or backward and modify specific characters in case an error is made (in the original game, a single error would force the player to reset the game or intentionally submit an incorrect password to reset the password menu). Passwords were also condensed to eight characters. These changes were retained for the next three games, save for differences in character sets. Bomberman for the PC-Engine utilized letters A through Z. Bomberman II condensed the character set to numerals 1 through 8 and letters B through K, excluding vowels. Bomberman '93's character set ranged from B to Z, also excluding vowels.Super Bomberman, the four-digit password system was first introduced. This system became the standard for the rest of the series. Along with this simplified password system came the addition of secret passwords that produce different effects, such as the "Mini Bomberman" password (which makes all Bombermen appear much smaller than usual) and the "Sound Test Mode". The password 5656, originally used to produce the "Mini Bomberman" effect, became a staple throughout the rest of the series, often being used for other special modes such as activating Sudden Death in the Battle Game or enabling the Golden Bomber effect.
- Bomberman PCE Japanese manual, Hudson Soft, 1990, pg. 3.
- Bomberman TG-16 U.S. manual, NEC Technologies, 1991, pg. 3.
- Bomberman Operation Manual, NES-BM-USA, Hudson Soft USA, 1989, pp. 2, 4-7
- ボンバーマン 取扱説明書, HFC-BM, Hudson Soft, 1985, pp. 1, 6-8
- Super Bomberman Hudson Official Guidebook. Shogakukan, 1993, pp. 106-107, 110, 112.
- Super Bomberman 2 Hudson Official Guidebook, Shogakukan, 1994, p. 108.
- Super Bomberman 3 Hudson Official Guidebook, Shogakukan, 1995, p. 111.