How To Write Unmaintainable Code
Naming

"When I use a word," Humpty Dumpty said, in a rather scornful tone, "it means just what I choose it to mean - neither more nor less."

Lewis Carroll -- Through the Looking Glass, Chapter 6

Much of the skill in writing unmaintainable code is the art of naming variables and methods. They don't matter at all to the compiler. That gives you huge latitude to use them to befuddle the maintenance programmer.

New Uses For Names For Baby
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20,001 Names For Baby

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Carol McD. Wallace

Buy a copy of a baby naming book and you'll never be at a loss for variable names. Fred is a wonderful name, and easy to type. If you're looking for easy-to-type variable names, try adsf or aoeu if you type with a DSK keyboard.
Single Letter Variable Names
: If you call your variables a, b, c, then it will be impossible to search for instances of them using a simple text editor. Further, nobody will be able to guess what they are for. If anyone even hints at breaking the tradition honoured since FØRTRAN of using i, j, and k for indexing variables, namely replacing them with ii, jj and kk, warn them about what the Spanish Inquisition did to heretics.
Creative Miss-spelling
: If you must use descriptive variable and function names, misspell them. By misspelling in some function and variable names, and spelling it correctly in others (such as SetPintleOpening SetPintalClosing) we effectively negate the use of grep or IDE search techniques. It works amazingly well. Add an international flavor by spelling tory or tori in different theatres/theaters.
Be Abstract
: In naming functions and variables, make heavy use of abstract words like it, everything, data, handle, stuff, do, routine, perform and the digits e.g. routineX48, PerformDataFunction, DoIt, HandleStuff and do_args_method.
A.C.R.O.N.Y.M.S.
: Use acronyms to keep the code terse. Real men never define acronyms; they understand them genetically.
Thesaurus Surrogatisation
: To break the boredom, use a thesaurus to look up as much alternate vocabulary as possible to refer to the same action, e.g. display, show, present. Vaguely hint there is some subtle difference, where none exists. However, if there are two similar functions that have a crucial difference, always use the same word in describing both functions (e.g. print to mean "write to a file", "put ink on paper" and "display on the screen"). Under no circumstances, succumb to demands to write a glossary with the special purpose project vocabulary unambiguously defined. Doing so would be an unprofessional breach of the structured design principle of information hiding.
Use Plural Forms From Other Languages
: A VMS script kept track of the "statii" returned from various "Vaxen". Esperanto, Klingon and Hobbitese qualify as languages for these purposes. For pseudo-Esperanto pluraloj, add oj. You will be doing your part toward world peace.
CapiTaliSaTion
:Randomly capitalize the first letter of a syllable in the middle of a word. For example: ComputeRasterHistoGram().
Reuse Names
: Wherever the rules of the language permit, give classes, constructors, methods, member variables, parameters and local variables the same names. For extra points, reuse local variable names inside {} blocks. The goal is to force the maintenance programmer to carefully examine the scope of every instance. In particular, in Java, make ordinary methods masquerade as constructors.
Åccented Letters
: Use accented characters on variable names. E.g.
where the second ínt's í is actually i-acute. With only a simple text editor, it's nearly impossible to distinguish the slant of the accent mark.
Exploit Compiler Name Length Limits
: If the compiler will only distinguish the first, say, 8 characters of names, then vary the endings e.g. var_unit_update() in one case and var_unit_setup() in another. The compiler will treat both as var_unit.
Underscore, a Friend Indeed
: Use _ and __ as identifiers.
Mix Languages
: Randomly intersperse two languages (human or computer). If your boss insists you use his language, tell him you can organise your thoughts better in your own language, or, if that does not work, allege linguistic discrimination and threaten to sue your employers for a vast sum.
Extended ASCII
: Extended ASCII characters are perfectly valid as variable names, including ß, Ð, and ñ characters. They are almost impossible to type without copying/pasting in a simple text editor.
Names From Other Languages
: Use foreign language dictionaries as a source for variable names. For example, use the German punkt for point. Maintenance coders, without your firm grasp of German, will enjoy the multicultural experience of deciphering the meaning.
Names From Mathematics
: Choose variable names that masquerade as mathematical operators, e.g.:
Bedazzling Names
: Choose variable names with irrelevant emotional connotation. e.g.:
This confuses the reader because they have difficulty disassociating the emotional connotations of the words from the logic they're trying to think about.
Rename and Reuse
: This trick works especially well in Ada, a language immune to many of the standard obfuscation techniques. The people who originally named all the objects and packages you use were morons. Rather than try to convince them to change, just use renames and subtypes to rename everything to names of your own devising. Make sure to leave a few references to the old names in, as a trap for the unwary.
When To Use i
: Never use i for the innermost loop variable. Use anything but. Use i liberally for any other purpose especially for non-int variables. Similarly use n as a loop index.
Conventions Schmentions
: Ignore the Sun Java Coding Conventions, after all, Sun does. Fortunately, the compiler won't tattle when you violate them. The goal is to come up with names that differ subtlely only in case. If you are forced to use the capitalisation conventions, you can still subvert wherever the choice is ambigous, e.g. use both inputFilename and inputfileName. Invent your own hopelessly complex naming conventions, then berate everyone else for not following them.
Lower Case l Looks a Lot Like the Digit 1
: Use lower case l to indicate long constants. e.g. 10l is more likely to be mistaken for 101 that 10L is. Ban any fonts that clearly disambiguate uvw wW gq9 2z 5s il17|!j oO08 `'" ;: ,. m nn rn {[()]}. Be creative.
Reuse of Global Names as Private
: Declare a global array in module A, and a private one of the same name in the header file for module B, so that it appears that it's the global array you are using in module B, but it isn't. Make no reference in the comments to this duplication.
Recycling Revisited
: Use scoping as confusingly as possible by recycling variable names in contradictory ways. For example, suppose you have global variables A and B, and functions foo and bar. If you know that variable A will be regularly passed to foo and B to bar, make sure to define the functions as function foo(B) and function bar(A) so that inside the functions A will always be referred to as B and vice versa. With more functions and globals, you can create vast confusing webs of mutually contradictory uses of the same names.
Recycle Your Variables
: Wherever scope rules permit, reuse existing unrelated variable names. Similarly, use the same temporary variable for two unrelated purposes (purporting to save stack slots). For a fiendish variant, morph the variable, for example, assign a value to a variable at the top of a very long method, and then somewhere in the middle, change the meaning of the variable in a subtle way, such as converting it from a 0-based coordinate to a 1-based coordinate. Be certain not to document this change in meaning.
Cd wrttn wtht vwls s mch trsr
: When using abbreviations inside variable or method names, break the boredom with several variants for the same word, and even spell it out longhand once in while. This helps defeat those lazy bums who use text search to understand only some aspect of your program. Consider variant spellings as a variant on the ploy, e.g. mixing International colour, with American color and dude-speak kulerz. If you spell out names in full, there is only one possible way to spell each name. These are too easy for the maintenance programmer to remember. Because there are so many different ways to abbreviate a word, with abbreviations, you can have several different variables that all have the same apparent purpose. As an added bonus, the maintenance programmer might not even notice they are separate variables.
Misleading names
: Make sure that every method does a little bit more (or less) than its name suggests. As a simple example, a method named isValid(x) should as a side effect convert x to binary and store the result in a database.
m_
: a naming convention from the world of C++ is the use of "m_" in front of members. This is supposed to help you tell them apart from methods, so long as you forget that "method" also starts with the letter "m".
o_apple obj_apple
: Use an "o" or "obj" prefix for each instance of the class to show that you're thinking of the big, polymorphic picture.
Hungarian Notation
: Hungarian Notation is the tactical nuclear weapon of source code obfuscation techniques; use it! Due to the sheer volume of source code contaminated by this idiom nothing can kill a maintenance engineer faster than a well planned Hungarian Notation attack. The following tips will help you corrupt the original intent of Hungarian Notation:
- Insist on using "c" for const in C++ and other languages that directly enforce the const-ness of a variable.
- Seek out and use Hungarian warts that have meaning in languages other than your current language. For example insist on the PowerBuilder "l_" and "a_ " {local and argument} scoping prefixes and always use the VB-esque style of having a Hungarian wart for every control type when coding to C++. Try to stay ignorant of the fact that megs of plainly visible MFC source code does not use Hungarian warts for control types.
- Always violate the Hungarian principle that the most commonly used variables should carry the least extra information around with them. Achieve this end through the techniques outlined above and by insisting that each class type have a custom wart prefix. Never allow anyone to remind you that no wart tells you that something is a class. The importance of this rule cannot be overstated: if you fail to adhere to its principles the source code may become flooded with shorter variable names that have a higher vowel/consonant ratio. In the worst case scenario this can lead to a full collapse of obfuscation and the spontaneous reappearance of English Notation in code!
- Flagrantly violate the Hungarian-esque concept that function parameters and other high visibility symbols must be given meaningful names, but that Hungarian type warts all by themselves make excellent temporary variable names.
- Insist on carrying outright orthogonal information in your Hungarian warts. Consider this real world example: "a_crszkvc30LastNameCol". It took a team of maintenance engineers nearly 3 days to figure out that this whopper variable name described a const, reference, function argument that was holding information from a database column of type Varchar[30] named "LastName" which was part of the table's primary key. When properly combined with the principle that "all variables should be public" this technique has the power to render thousands of lines of source code obsolete instantly!
- Use to your advantage the principle that the human brain can only hold 7 pieces of information concurrently. For example code written to the above standard has the following properties:
  - a single assignment statement carries 14 pieces of type and name information.
  - a single function call that passes three parameters and assigns a result carries 29 pieces of type and name information.
  - Seek to improve this excellent, but far too concise, standard. Impress management and coworkers by recommending a 5 letter day of the week prefix to help isolate code written on 'Monam' and 'FriPM'.
  - It is easy to overwhelm the short term memory with even a moderately complex nesting structure, especially when the maintenance programmer can't see the start and end of each block on screen simultaneously.
Hungarian Notation Revisited
: One followon trick in the Hungarian notation is "change the type of a variable but leave the variable name unchanged". This is almost invariably done in windows apps with the migration from Win16 :- WndProc(HWND hW, WORD wMsg, WORD wParam, LONG lParam) to Win32 WndProc(HWND hW, UINT wMsg, WPARAM wParam, LPARAM lParam) where the w values hint that they are words, but they really refer to longs. The real value of this approach comes clear with the Win64 migration, when the parameters will be 64 bits wide, but the old "w" and "l" prefixes will remain forever.
Reduce, Reuse, Recycle
: If you have to define a structure to hold data for callbacks, always call the structure PRIVDATA. Every module can define it's own PRIVDATA. In VC++, this has the advantage of confusing the debugger so that if you have a PRIVDATA variable and try to expand it in the watch window, it doesn't know which PRIVDATA you mean, so it just picks one.
Obscure film references
: Use constant names like LancelotsFavouriteColour instead of blue and assign it hex value of $0204FB. The color looks identical to pure blue on the screen, and a maintenance programmer would have to work out 0204FB (or use some graphic tool) to know what it looks like. Only someone intimately familiar with Monty Python and the Holy Grail would know that Lancelot's favorite color was blue. If a maintenance programmer can't quote entire Monty Python movies from memory, he or she has no business being a programmer.