Integer overflow: Difference between revisions

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In the arcade game ''[[Donkey Kong (arcade 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>[[File:Error message due to an integer signedness bug in the stack setup code of MASM 1.00.gif|thumb|An integer signedness bug in the stack setup code emitted by the [[Pascal (programming language)|Pascal]] compiler prevented IBM–[[Microsoft Macro Assembler]] (MASM) version 1.00, a [[DOS]] program from 1981, and many other programs compiled with the same compiler, to run under some configurations with more than 512 KB of memory.]]

A similar glitch occurs in [[S.T.A.L.K.E.R.: Clear Sky]] where the player can drop into a negative amount by fast travelling without sufficient funds, then proceeding to the event where the player gets robbed and has all of their currency taken away. After the game attempts to take the player's money away to an amount of $0, the player is granted 2147482963 in game currency.<ref>{{Cite web |url=https://steamcommunity.com/app/20510/discussions/0/1484358860942756615/ |title=Money glitch :: S.T.A.L.K.E.R.: Clear Sky General Discussions}}</ref>

[[File:Error message due to an integer signedness bug in the stack setup code of MASM 1.00.gif|thumb|An integer signedness bug in the stack setup code emitted by the [[Pascal (programming language)|Pascal]] compiler prevented IBM–[[Microsoft Macro Assembler]] (MASM) version 1.00, a [[DOS]] program from 1981, and many other programs compiled with the same compiler, to run under some configurations with more than 512 KB of memory.]]

IBM–[[Microsoft Macro Assembler]] (MASM) version 1.00, and likely all other programs built by the same [[Pascal (programming language)|Pascal]] compiler, had an integer overflow and signedness error in the stack setup code, which prevented them from running on newer [[DOS]] machines or emulators under some common configurations with more than 512 KB of memory. The program either hangs or displays an error message and exits to DOS.<ref>{{cite web |last=Lenclud |first=Christophe |url=https://slions.net/threads/debugging-the-ibm-personal-computer-macro-assembler-masm-version-1-00.33/ |title=Debugging IBM MACRO Assembler Version 1.00}}</ref>