Why shouldn t I use Hungarian Notation

Question

I know what Hungarian refers to - giving information about a variable  parameter  or type as a prefix to its name  Everyone seems to be rabidly against it  even though in some cases it seems to be a good idea  If I feel that useful information is being imparted  why shouldn t I put it right there where it s available   See also  Do people use the Hungarian naming conventions in the real world

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Joel is wrong  and here is why   That  application  information he s talking about should be encoded in the type system  You should not depend on flipping variable names to make sure you don t pass unsafe data to functions requiring safe data  You should make it a type error  so that it is impossible to do so  Any unsafe data should have a type that is marked unsafe  so that it simply cannot be passed to a safe function  To convert from unsafe to safe should require processing with some kind of a sanitize function   A lot of the things that Joel talks of as  kinds  are not kinds  they are  in fact  types   What most languages lack  however  is a type system that s expressive enough to enforce these kind of distinctions   For example  if C had a kind of  strong typedef   where the typedef name had all the operations of the base type  but was not convertible to it  then a lot of these problems would go away  For example  if you could say  strong typedef std  string unsafe string  to introduce a new type unsafe string that could not be converted to a std  string  and so could participate in overload resolution etc  etc   then we would not need silly prefixes   So  the central claim that Hungarian is for things that are not types is wrong  It s being used for type information  Richer type information than the traditional C type information  certainly  it s type information that encodes some kind of semantic detail to indicate the purpose of the objects  But it s still type information  and the proper solution has always been to encode it into the type system  Encoding it into the type system is far and away the best way to obtain proper validation and enforcement of the rules   Variables names simply do not cut the mustard   In other words  the aim should not be  make wrong code look wrong to the developer    It should be  make wrong code look wrong to the compiler

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Joel s article is great  but it seems to omit one major point   Hungarian makes a particular  idea   kind   identifier name  unique  or near-unique  across the codebase - even a very large codebase   That s huge for code maintenance   It means you can use good ol  single-line text search   grep  findstr   find in all files   to find EVERY mention of that  idea    Why is that important when we have IDE s that know how to read code  Because they re not very good at it yet  This is hard to see in a small codebase  but obvious in a large one - when the  idea  might be mentioned in comments  XML files  Perl scripts  and also in places outside source control  documents  wikis  bug databases    You do have to be a little careful even here - e g  token-pasting in C C   macros can hide mentions of the identifier  Such cases can be dealt with using  coding conventions  and anyway they tend to affect only a minority of the identifiers in the  codebase   P S  To the point about using the type system vs  Hungarian - it s best to use both  You only need wrong code to look wrong if the compiler won t catch it for you  There are plenty of cases where it is infeasible to make the compiler catch it  But where it s feasible - yes  please do that instead    When considering feasibility  though  do consider the negative effects of splitting up types  e g  in C   wrapping  int  with a non-built-in type has huge consequences  So it makes sense in some situations  but not in all of them

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The Hungarian notation was abused  particularly by Microsoft  leading to prefixes longer than the variable name  and showing it is quite rigid  particularly when you change the types  the infamous lparam wparam  of different type size in Win16  identical in Win32    Thus  both due to this abuse  and its use by M   it was put down as useless   At my work  we code in Java  but the founder cames from MFC world  so use similar code style  aligned braces  I like this   capitals to method names  I am used to that  prefix like m  to class members  fields   s  to static members  etc     And they said all variables should have a prefix showing its type  eg  a BufferedReader is named brData   Which shown as being a bad idea  as the types can change but the names doesn t follow  or coders are not consistent in the use of these prefixes  I even see aBuffer  theProxy  etc      Personally  I chose for a few prefixes that I find useful  the most important being b to prefix boolean variables  as they are the only ones where I allow syntax like if  bVar   no use of autocast of some values to true or false   When I coded in C  I used a prefix for variables allocated with malloc  as a reminder it should be freed later  Etc   So  basically  I don t reject this notation as a whole  but took what seems fitting for my needs  And of course  when contributing to some project  work  open source   I just use the conventions in place

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For years I used Hungarian notation in my programming  Other than some visual clutter and the task of changing the prefix when I changed the data type  no one could convince me otherwise  Until recently--when I had to combine existing C  and VB NET assemblies in the same solution   The result  I had to pass a  fltSomeVariable  to a  sngSomeVariable  method parameter  Even as someone who programs in both C  and VB NET  it caught me off guard and made me pause for a moment   C  and VB NET sometimes use different names to represent the same data type--float and single  for example    Now consider this  what if you create a COM component that s callable from many languages  The VB NET and C   conversion  was easy for a  NET programmer  But what about someone that develops in C   or Java  Does  dwSomeVariable  mean anything to a  NET developer not familiar with C

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vUsing adjHungarian nnotation vmakes nreading ncode adjdifficult

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Hungarian Notation can be useful in languages without compile-time type checking  as it would allow developer to quickly remind herself of how the particular variable is used  It does nothing for performance or behavior  It is supposed to improve code readability and is mostly a matter a taste and coding style  For this very reason it is criticized by many developers -- not everybody has the same wiring in the brain   For the compile-time type-checking languages it is mostly useless -- scrolling up a few lines should reveal the declaration and thus type  If you global variables or your code block spans for much more than one screen  you have grave design and reusability issues  Thus one of the criticisms is that Hungarian Notation allows developers to have bad design and easily get away with it  This is probably one of the reasons for hatered   On the other hand  there can be cases where even compile-time type-checking languages would benefit from Hungarian Notation -- void pointers or HANDLE s in win32 API  These obfuscates the actual data type  and there might be a merit to use Hungarian Notation there  Yet  if one can know the type of data at build time  why not to use the appropriate data type   In general  there are no hard reasons not to use Hungarian Notation  It is a matter of likes  policies  and coding style

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Tacking on cryptic characters at the beginning of each variable name is unnecessary and shows that the variable name by itself isn t descriptive enough  Most languages require the variable type at declaration anyway  so that information is already available   There s also the situation where  during maintenance  a variable type needs to change  Example  if a variable declared as  uint 16 u16foo  needs to become a 64-bit unsigned  one of two things will happen    You ll go through and change each variable name  making sure not to hose any unrelated variables with the same name   or Just change the type and not change the name  which will only cause confusion

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I started coding pretty much the about the time Hungarian notation was invented and the first time I was forced to use it on a project I hated it   After a while I realised that when it was done properly it did actually help and these days I love it    But like all things good  it has to be learnt and understood and to do it properly takes time

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I think it massively clutters up the source code   It also doesn t gain you much in a strongly typed language   If you do any form of type mismatch tomfoolery  the compiler will tell you about it

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Im my experience  it is bad because   1 - then you break all the code if you need to change the type of a variable  i e  if you need to extend a 32 bits integer to a 64 bits integer    2 - this is useless information as the type is either already in the declaration or you use a dynamic language where the actual type should not be so important in the first place   Moreover  with a language accepting generic programming  i e  functions where the type of some variables is not determine when you write the function  or with dynamic typing system  i e  when the type is not even determine at compile time   how would you name your variables  And most modern languages support one or the other  even if in a restricted form

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Hungarian is bad because it takes precious characters away from variable names in exchange for what  some type information   First of all  in a strongly typed language  the compiler will warn you if you do any truly stupid   Second  if you believe in good modularized code and don t do too much work in any 1 function  you re variables are probable declared just above the code they are used in anyway  so you have the type right there    Third  if you prefix every pointer with p and every class with C  your really screwing up your nice modern IDE s ability to do intellisense  you know that feature where it guesses as you type what class name your typing and as soon as it gets it right you can hit enter and it completes it for you  well  if you prefix every class with C  you always have at least 1 extra letter to type

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I cannot find a link but I remember reading somewhere  which I agree with  that avoiding Hungarian notation results in better programming style   When you program a statement of your program  you should not be thinking about  what type this object is  before calling its method  but rather you should think  what do I want to do with it    which message to send to it    Kind of vague concept to explain  but I think it works   For example  if you have customer name stored in variable customerName  you should not care if it is a string or some other class  More important to think what do you want from this object  Do you want it to print    getFirstName    getLastName    convertToString   etc  Once you make it an instance of String class and take it as granted  you limit yourself and your design since you have to build up all other logic you need elsewhere in the code

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You re forgetting the number one reason to include this information   It has nothing to do with you  the programmer   It has everything to do with the person coming down the road 2 or 3 years after you leave the company who has to read that stuff   Yes  an IDE will quickly identify types for you   However  when you re reading through some long batches of  business rules  code  it s nice to not have to pause on each variable to find out what type it is   When I see things like strUserID  intProduct or guiProductID  it makes for much easier  ramp up  time   I agree that MS went way too far with some of their naming conventions - I categorize that in the  too much of a good thing  pile   Naming conventions are good things  provided you stick to them   I ve gone through enough old code that had me constantly going back to look at the definitions for so many similarly-named variables that I push  camel casing   as it was called at a previous job    Right now I m on a job that has many thousand of lines of completely uncommented classic ASP code with VBScript and it s a nightmare trying to figure things out

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Joel Spolsky wrote a good blog post about this  http   www joelonsoftware com articles Wrong html Basically it comes down to not making your code harder to read when a decent IDE will tell you want type the variable is if you can t remember   Also  if you make your code compartmentalized enough  you don t have to remember what a variable was declared as three pages up

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The IDE should impart that useful information  Hungarian might have made some sort  not a whole lot  but some sort  of sense when IDE s were much less advanced

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Most people use Hungarian notation in a wrong way and are getting wrong results    Read this excellent article by Joel Spolsky  Making Wrong Code Look Wrong   In short  Hungarian Notation where you prefix your variable names with their type  string   Systems Hungarian  is bad because it s useless   Hungarian Notation as it was intended by its author where you prefix the variable name with its kind  using Joel s example  safe string or unsafe string   so called Apps Hungarian has its uses and is still valuable

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I cannot find a link but I remember reading somewhere  which I agree with  that avoiding Hungarian notation results in better programming style   When you program a statement of your program  you should not be thinking about  what type this object is  before calling its method  but rather you should think  what do I want to do with it    which message to send to it    Kind of vague concept to explain  but I think it works   For example  if you have customer name stored in variable customerName  you should not care if it is a string or some other class  More important to think what do you want from this object  Do you want it to print    getFirstName    getLastName    convertToString   etc  Once you make it an instance of String class and take it as granted  you limit yourself and your design since you have to build up all other logic you need elsewhere in the code

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I tend to use Hungarian Notation with ASP NET server controls only  otherwise I find it too hard to work out what controls are what on the form   Take this code snippet    lt asp Label ID  lblFirstName  runat  server  Text  First Name    gt   lt asp TextBox ID  txtFirstName  runat  server    gt   lt asp RequiredFieldValidator ID  rfvFirstName  runat  server        gt    If someone can show a better way of having that set of control names without Hungarian I d be tempted to move to it

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It s a useful convention for naming controls on a form  btnOK  txtLastName etc    if the list of controls shows up in an alphabetized pull-down list in your IDE

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If I feel that useful information is being imparted  why shouldn t I put it right there where it s available    Then who cares what anybody else thinks   If you find it useful  then use the notation

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Several reasons    Any modern IDE will give you the variable type by simply hovering your mouse over the variable  Most type names are way long  think HttpClientRequestProvider  to be reasonably used as prefix  The type information does not carry the right information  it is just paraphrasing the variable declaration  instead of outlining the purpose of the variable  think myInteger vs  pageSize

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Isn t scope more important than type these days  e g     l for local   a for argument   m for member   g for global   etc   With modern techniques of refactoring old code  search and replace of a symbol because you changed its type is tedious  the compiler will catch type changes  but often will not catch incorrect use of scope  sensible naming conventions help here

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If you don t know the type of a variable without being told  you probably shouldn t be messing with it anyways  The type might also not be that important  If you know what the methods do  you can figure out what is being done with the variable and then you ll what the program is doing  There may be times you want it  when type is important and the declaration isn t near or the type can t be inferred with ease  But it should never be seen as absolute

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As a Python programmer  Hungarian Notation falls apart pretty fast  In Python  I don t care if something is a string - I care if it can act like a string  i e  if it has a    str      method which returns a string    For example  let s say we have foo as an integer  12  foo   12   Hungarian notation tells us that we should call that iFoo or something  to denote it s an integer  so that later on  we know what it is  Except in Python  that doesn t work  or rather  it doesn t make sense  In Python  I decide what type I want when I use it  Do I want a string  well if I do something like this   print  The current value of foo is  s    foo   Note the  s - string  Foo isn t a string  but the   operator will call foo    str      and use the result  assuming it exists   foo is still an integer  but we treat it as a string if we want a string  If we want a float  then we treat it as a float  In dynamically typed languages like Python  Hungarian Notation is pointless  because it doesn t matter what type something is until you use it  and if you need a specific type  then just make sure to cast it to that type  e g  float foo   when you use it   Note that dynamic languages like PHP don t have this benefit - PHP tries to do  the right thing  in the background based on an obscure set of rules that almost no one has memorized  which often results in catastrophic messes unexpectedly  In this case  some sort of naming mechanism  like  files count or  file name  can be handy   In my view  Hungarian Notation is like leeches  Maybe in the past they were useful  or at least they seemed useful  but nowadays it s just a lot of extra typing for not a lot of benefit

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Debunking the benefits of Hungarian Notation   It provides a way of distinguishing variables    If the type is all that distinguishes the one value from another  then it can only be for the conversion of one type to another   If you have the same value that is being converted between types  chances are you should be doing this in a function dedicated to conversion   I have seen hungarianed VB6 leftovers use strings on all of their method parameters simply because they could not figure out how to deserialize a JSON object  or properly comprehend how to declare or use nullable types     If you have two variables distinguished only by the Hungarian prefix  and they are not a conversion from one to the other  then you need to elaborate on your intention with them    It makes the code more readable    I have found that Hungarian notation makes people lazy with their variable names   They have something to distinguish it by  and they feel no need to elaborate to its purpose   This is what you will typically find in Hungarian notated code vs  modern  sSQL vs  groupSelectSql  or usually no sSQL at all because they are supposed to be using the ORM that was put in by earlier developers    sValue vs  formCollectionValue  or usually no sValue either  because they happen to be in MVC and should be using its model binding features   sType vs  publishSource  etc   It can t be readability   I see more sTemp1  sTemp2    sTempN from any given hungarianed VB6 leftover than everybody else combined    It prevents errors    This would be by virtue of number 2  which is false

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I ve always thought that a prefix or two in the right place wouldn t hurt  I think if I can impart something useful  like  Hey this is an interface  don t count on specific behaviour  right there  as in IEnumerable  I oughtta do it  Comment can clutter things up much more than just a one or two character symbol

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For years I used Hungarian notation in my programming  Other than some visual clutter and the task of changing the prefix when I changed the data type  no one could convince me otherwise  Until recently--when I had to combine existing C  and VB NET assemblies in the same solution   The result  I had to pass a  fltSomeVariable  to a  sngSomeVariable  method parameter  Even as someone who programs in both C  and VB NET  it caught me off guard and made me pause for a moment   C  and VB NET sometimes use different names to represent the same data type--float and single  for example    Now consider this  what if you create a COM component that s callable from many languages  The VB NET and C   conversion  was easy for a  NET programmer  But what about someone that develops in C   or Java  Does  dwSomeVariable  mean anything to a  NET developer not familiar with C

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If you don t know the type of a variable without being told  you probably shouldn t be messing with it anyways  The type might also not be that important  If you know what the methods do  you can figure out what is being done with the variable and then you ll what the program is doing  There may be times you want it  when type is important and the declaration isn t near or the type can t be inferred with ease  But it should never be seen as absolute

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In the words of the master   http   www joelonsoftware com articles Wrong html  An interesting reading  as usual   Extracts    Somebody  somewhere  read Simonyi   s paper  where he used the word    type     and thought he meant type  like class  like in a type system  like the type checking that the compiler does  He did not  He explained very carefully exactly what he meant by the word    type     but it didn   t help  The damage was done     But there   s still a tremendous amount of value to Apps Hungarian  in that it increases collocation in code  which makes the code easier to read  write  debug  and maintain  and  most importantly  it makes wrong code look wrong    Make sure you have some time before reading Joel On Software

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I always use Hungarian notation for all my projects  I find it really helpful when I m dealing with 100s of different identifier names   For example  when I call a function requiring a string I can type  s  and hit control-space and my IDE will show me exactly the variable names prefixed with  s      Another advantage  when I prefix u for unsigned and i for signed ints  I immediately see where I am mixing signed and unsigned in potentially dangerous ways    I cannot remember the number of times when in a huge 75000 line codebase  bugs were caused  by me and others too  due to naming local variables the same as existing member variables of that class  Since then  I always prefix members with  m    Its a question of taste and experience  Don t knock it until you ve tried it

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Hungarian notation only makes sense in languages without user-defined types  In a modern functional or OO-language  you would encode information about the  kind  of value into the datatype or class rather than into the variable name   Several answers reference Joels article  Note however that his example is in VBScript  which didn t support user-defined classes  for a long time at least   In a language with user-defined types you would solve the same problem by creating a HtmlEncodedString-type and then let the Write method accept only that  In a statically typed language  the compiler will catch any encoding-errors  in a dynamically typed you would get a runtime exception - but in any case you are protected against writing unencoded strings  Hungarian notations just turns the programmer into a human type-checker  with is the kind of job that is typically better handled by software   Joel distinguishes between  systems hungarian  and  apps hungarian   where  systems hungarian  encodes the built-in types like int  float and so on  and  apps hungarian  encodes  kinds   which is higher-level meta-info about variable beyound the machine type  In a OO or modern functional language you can create user-defined types  so there is no distinction between type and  kind  in this sense - both can be represented by the type system - and  apps  hungarian is just as redundant as  systems  hungarian   So to answer your question  Systems hungarian would only be useful in a unsafe  weakly typed language where e g  assigning a float value to an int variable will crash the system  Hungarian notation was specifically invented in the sixties for use in BCPL  a pretty low-level language which didn t do any type checking at all  I dont think any language in general use today have this problem  but the notation lived on as a kind of cargo cult programming   Apps hungarian will make sense if you are working with a language without user defined types  like legacy VBScript or early versions of VB  Perhaps also early versions of Perl and PHP  Again  using it in a modern languge is pure cargo cult   In any other language  hungarian is just ugly  redundant and fragile  It repeats information already known from the type system  and you should not repeat yourself  Use a descriptive name for the variable that describes the intent of this specific instance of the type  Use the type system to encode invariants and meta info about  kinds  or  classes  of variables - ie  types   The general point of Joels article - to have wrong code look wrong - is a very good principle  However an even better protection against bugs is to - when at all possible - have wrong code to be detected automatically by the compiler

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Of course when 99  of programmers agree on something  there is something wrong  The reason they agree here is because most of them have never used Hungarian notation correctly   For a detailed argument  I refer you to a blog post I have made on the subject   http   codingthriller blogspot com 2007 11 rediscovering-hungarian-notation html

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I don t think everyone is rabidly against it   In languages without static types  it s pretty useful   I definitely prefer it when it s used to give information that is not already in the type   Like in C  char   szName says that the variable will refer to a null terminated string -- that s not implicit in char  -- of course  a typedef would also help   Joel had a great article on using hungarian to tell if a variable was HTML encoded or not   http   www joelonsoftware com articles Wrong html  Anyway  I tend to dislike Hungarian when it s used to impart information I already know

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There is no reason why you should not make correct use of Hungarian notation  It s unpopularity is due to a long-running back-lash against the mis-use of Hungarian notation  especially in the Windows APIs   In the bad-old days  before anything resembling an IDE existed for DOS  odds are you didn t have enough free memory to run the compiler under Windows  so your development was done in DOS   you didn t get any help from hovering your mouse over a variable name   Assuming you had a mouse   What did you did have to deal with were event callback functions in which everything was passed to you as either a 16-bit int  WORD  or 32-bit int  LONG WORD   You then had to cast those parameter to the appropriate types for the given event type  In effect  much of the API was virtually type-less   The result  an API with parameter names like these   LRESULT CALLBACK WindowProc HWND hwnd                              UINT uMsg                              WPARAM wParam                              LPARAM lParam     Note that the names wParam and lParam  although pretty awful  aren t really any worse than naming them param1 and param2   To make matters worse  Window 3 0 3 1 had two types of pointers  near and far  So  for example  the return value from memory management function LocalLock was a PVOID  but the return value from GlobalLock was an LPVOID  with the  L  for long   That awful notation then got extended so that a long pointer string was prefixed lp  to distinguish it from a string that had simply been malloc d   It s no surprise that there was a backlash against this sort of thing

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In Joel Spolsky s Making Wrong Code Look Wrong he explains that what everybody thinks of as Hungarian Notation  which he calls Systems Hungarian  is not what was it was really intended to be  what he calls Apps Hungarian    Scroll down to the I   m Hungary heading to see this discussion   Basically  Systems Hungarian is worthless   It just tells you the same thing your compiler and or IDE will tell you   Apps Hungarian tells you what the variable is supposed to mean  and can actually be useful

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They re a humongous eyesore Your IDE should be able to tell you all you need to know about a variable s type Good names  which HN gets in the way of  should communicate to you everything else you need to know about a variable

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See also What kind of prefix do you use for member variables

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I think the whole thing of the aesthetical aspect is over-hyped  If that was the most important thing  we would not call ourselves developers  but graphic designers   One important part  I think  is that you decribe what your objects role is  not what it is  You don t call yourself HumanDustman  becuase in another context  you would not most importantly be a human   For refactoring-purposes it s really important too   public string stringUniqueKey    ABC-12345     What if you decide to use a GUID instead of a string  your variable name would look stupid after refactoring all refering code   Or   public int intAge   20    Changing this to a float  you would have the same problem  And so on

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Apps Hungarian is Greek to me--in a good way  As an engineer  not a programmer  I immediately took to Joel s article on the merits of Apps Hungarian   Making Wrong Code Look Wrong   I like Apps Hungarian because it mimics how engineering  science  and mathematics represent equations and formulas using sub- and super-scripted symbols  like Greek letters  mathematical operators  etc    Take a particular example of Newton s Law of Universal Gravity  first in standard mathematical notation  and then in Apps Hungarian pseudo-code     frcGravityEarthMars   G   massEarth   massMars   norm posEarth - posMars    In the mathematical notation  the most prominent symbols are those representing the kind of information stored in the variable  force  mass  position vector  etc  The subscripts play second fiddle to clarify  position of what  This is exactly what Apps Hungarian is doing  it s telling you the kind of thing stored in the variable first and then getting into specifics--about the closest code can get to mathematical notation    Clearly strong typing can resolve the safe vs  unsafe string example from Joel s essay  but you wouldn t define separate types for position and velocity vectors  both are double arrays of size three and anything you re likely to do to one might apply to the other  Furthermore  it make perfect sense to concatenate position and velocity  to make a state vector  or take their dot product  but probably not to add them  How would typing allow the first two and prohibit the second  and how would such a system extend to every possible operation you might want to protect  Unless you were willing to encode all of math and physics in your typing system    On top of all that  lots of engineering is done in weakly typed high-level languages like Matlab  or old ones like Fortran 77 or Ada   So if you have a fancy language and IDE and Apps Hungarian doesn t help you then forget it--lots of folks apparently have  But for me  a worse than a novice programmer who is working in weakly or dynamically typed languages  I can write better code faster with Apps Hungarian than without

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It s incredibly redundant and useless is most modern IDEs  where they do a good job of making the type apparent   Plus -- to me -- it s just annoying to see intI  strUserName  etc

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I tend to use Hungarian Notation with ASP NET server controls only  otherwise I find it too hard to work out what controls are what on the form   Take this code snippet    lt asp Label ID  lblFirstName  runat  server  Text  First Name    gt   lt asp TextBox ID  txtFirstName  runat  server    gt   lt asp RequiredFieldValidator ID  rfvFirstName  runat  server        gt    If someone can show a better way of having that set of control names without Hungarian I d be tempted to move to it

[language-agnostic] Why shouldn't I use "Hungarian Notation"?

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