Update

hacking.md

@@ -51,6 +51,7 @@ A great many commonly used tricks in programming could be regarded as hacks even
 
 - **[bit hacks](bit_hack.md)**: Clever manipulations of [bits](bit.md) -- for example it is possible to swap two variable without a temporary variables by using the [xor](xor.md) function. Another simplest example is implementing division by 2 as binary shift by 1 (this hack is used in real life by people for quickly dividing by 10, we just remove the last digit).
 - **[copyleft](copyleft.md)**: A legal hack by [Richard Stallman](rms.md), connected to [free software](free_software.md), working on the basis of the following idea: "If [copyright](copyright.md) lets me put any conditions on my work, I may impose a condition on my work that says that any modified version must not impose any restrictive conditions".
+- In minimalist [C](c.md) programming mainly two standards of the language are used: C89 and C99. To distinguish between them in source code one can e.g. exploit the fact that C99 introduced line comments (starting with `//`) and make such code that C99 sees part of it commented out while C89 doesn't. For example the following two lines: `int isC89 = 1 //**/ 2`, `; isC89 = !isC89;`.
 - **[fast inverse square root](fast_inverse_sqrt.md)**: Famous hack that was used in the [game](game.md) Quake, it [approxmates](approximation.md) an inverse of [square root](sqrt.md) of a [floating point](float.md) number by treating it as an integer and bashing it with a [magic constant](magic_constant.md), which is about four times faster than computing the value with the obvious floating point division.
 - **memory [rape](rape.md) in [C](c.md)**: E.g. instead of doing proper memory allocation with potentially inefficient and bloated `malloc` one may try to do a custom memory allocation without any libraries by abusing allocation on stack -- allocate a variable size array in main, set some global pointer to it and then manage this chunk of memory with your own allocation functions.
 - **actually portable executable** (https://justine.lol/ape.html): Justine Tunney found a way to create an executable format that passes as a valid NATIVE executable on all major systems including [GNU](gnu.md)/[Linux](linux.md), [Windows](windows.md) and [Mac](mac.md), i.e. it is possible to compile a native program (e.g. with [C](c.md)) and then have it natively run on any major OS.
@@ -60,6 +61,7 @@ A great many commonly used tricks in programming could be regarded as hacks even
 - **[quine](quine.md)**: A cleverly constructed self-replicating program in [programming language](programming_language.md) that prints its own source code -- this is a common exercise of language hackers.
 - **MetaGolfScript [esoteric languages](esolang.md)**: rather than being a nicely designed [code golfing](code_golf.md) language MetaGolfScript invents infinitely many languages, each of which solves one problem with a zero-length program, making it possible to win any golfing contest that allows arbitrary choice of language just by choosing the correct MetaGolfScript language.
 - **Appending "in Minecraft" to avoid legal responsibility**: some people try to avoid legal responsibility for threats by talking about the situation as if it was harmlessly happening in a video game such as Minecraft, for example "Bitch I'm going to come to your house and murder you in sleep, in Minecraft." Though this is a nice hack and should work, the dystopian governments can do whatever they want and still arrest you for this -- this happened e.g. in New Jersey when one guy threatened to kill a sheriff like this.
+- **[polyglot](polyglot.md) programs**: another fun activity by programming language enthusiasts; a polyglot is source code that's a valid in more than one programming language.
 - [Richard Stallman](rms.md) called some musical compositions hacks, specifically 4'33 (just silence) and Ma Fin Est Mon Commencement ([palindromic](palindrome.md) music).
 - TODO: moar