Integer overflow: Difference between revisions

Revision as of 21:21, 14 April 2023

Revision as of 21:48, 25 April 2023

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Overflow bugs are evident in some computer games. In ''[[Super Mario Bros.]]'' for the [[NES]], the stored number of lives is a signed byte (ranging from −128 to 127) meaning the player can safely have 127 lives, but when the player reaches their 128th life, the counter rolls over to zero lives (although the number counter is glitched before this happens) and stops keeping count. As such, if the player then dies it's an immediate game over. This is caused by the game's data overflow that was an error of programming as the developers may not have thought said number of lives could be earned.

In the arcade game ''[[Donkey Kong (videoarcade game)|Donkey Kong]]'', it is impossible to advance past level 22 due to an integer overflow in its time/bonus. The game calculates the time/bonus by taking the level number a user is on, multiplying it by 10, and adding 40. When they reach level 22, the time/bonus number is 260, which is too large for its 8-bit 256 value register, so it overflows to a value of 4 – too short to finish the level. In ''[[Donkey Kong Jr. Math]]'', when trying to calculate a number over 10,000, it shows only the first 4 digits. Overflow is the cause of the famous [[kill screen|"split-screen" level]] in ''[[Pac-Man]]''.<ref>{{cite web |url=http://home.comcast.net/~jpittman2/pacman/pacmandossier.html |title=The Pac-Man Dossier |last=Pittman |first=Jamey}}</ref> Such a bug also caused the ''Far Lands'' in ''[[Minecraft]]'' Java Edition which existed from the Infdev development period to Beta 1.7.3; it was later fixed in Beta 1.8. The same bug also existed in ''Minecraft'' Bedrock Edition but has since been fixed.<ref>{{cite web |url=http://minecraft.gamepedia.com/Far_Lands |title=Minecraft Gamepedia Page |website=Minecraft Gamepedia}}</ref>

In the [[Super Nintendo Entertainment System]] (SNES) game [[Lamborghini American Challenge]], the player can cause their amount of money to drop below $0 during a race by being fined over the limit of remaining money after paying the fee for a race, which glitches the integer and grants the player $65,535,000 more than it would have had after going negative.<ref>Archived at [https://ghostarchive.org/varchive/youtube/20211205/aNQdQPi0xMo Ghostarchive]{{cbignore}} and the [https://web.archive.org/web/20190726012137/https://www.youtube.com/watch?v=aNQdQPi0xMo&t=17m55s Wayback Machine]{{cbignore}}: {{cite web |url=https://www.youtube.com/watch?v=aNQdQPi0xMo&t=17m55s |title=Lamborghini American Challenge SPEEDRUN (13:24) |website=[[YouTube]]}}{{cbignore}}</ref>