MissingNo. Pokemon are actually error handlers, seen in Red/Blue. Encountering one is the result of three computing events. The first is the game's random battle encounter system: each area assigns values to Pokemon in a data buffer, which the game accesses for the player's encounters with wild Pokemon. However, no values are assigned to this buffer on the east coast of the Cinnabar and Seafoam Island locations—the information from the previously visited area is used instead. The second factor is the in-game tutorial, which temporarily stores the player's name in the data buffer. This causes the game to access the hexadecimal values of the player's name for Pokemon encounters at Cinnabar and Seafoam Island. The third factor is the game's error handling system; if the game selects a value from the data buffer that is not an existing Pokemon, a subroutine is triggered that causes the appearance of a Pokemon named MissingNo., short for "Missing Number".