Naming convention - underscore in C and C variables

Question

It s common to see a  var variable name in a class field  What does the underscore mean  Is there a reference for all these special naming conventions

User · Answer

The Microsoft naming standard for C  says variables and parameters should use the lower camel case form IE  paramName  The standard also calls for fields to follow the same form but this can lead to unclear code so many teams call for an underscore prefix to improve clarity IE   fieldName

User · Answer

The first commenter  R Samuel Klatchko  referenced  What are the rules about using an underscore in a C   identifier  which answers the question about the underscore in C     In general  you are not supposed to use a leading underscore  as it is reserved for the implementer of your compiler   The code you are seeing with  var is probably either legacy code  or code written by someone that grew up using the old naming system which didn t frown on leading underscores    As other answers state  it used to be used in C   to identify class member variables   However  it has no special meaning as far as decorators or syntax goes   So if you want to use it  it will compile   I ll leave the C  discussion to others

User · Answer

It is best practice to NOT use UNDERSCORES before any variable name or parameter name in C    Names beginning with an underscore or a double underscore are RESERVED for the C   implementers  Names with an underscore are reserved for the library to work   If you have a read at the C   Coding Standard  you will see that in the very first page it says       Don t overlegislate naming  but do use a consistent naming convention  There are only two must-dos  a  never use  underhanded names   ones that begin with an underscore or that contain a double underscore    p2   C   Coding Standards  Herb Sutter and Andrei Alexandrescu    More specifically  the ISO working draft states the actual rules      In addition  some identifiers are reserved for use by C    implementations and shall not be used otherwise  no diagnostic is required   a  Each identifier that contains a double underscore    or begins with an underscore followed by an uppercase letter is reserved to the implementation for any use   b  Each identifier that begins with an underscore is reserved to the implementation for use as a name in the global namespace    It is best practice to avoid starting a symbol with an underscore in case you accidentally wander into one of the above limitations   You can see it for yourself why such use of underscores can be disastrous when developing a software   Try compiling a simple helloWorld cpp program like this   g   -E helloWorld cpp   You will see all that happens in the background  Here is a snippet      ios base  iostate   err   ios base  iostate ios base  goodbit      try                 streambuf type    sb   this- gt rdbuf           if    sb          if    sb- gt pubsync      -1          err    ios base  badbit      else         ret   0        You can see how many names begin with double underscore   Also if you look at virtual member functions  you will see that   vptr is the pointer generated for the virtual table which automatically gets created when you use one or more virtual member functions in your class  But that s another story     If you use underscores you might get into conflict issues and you WILL HAVE NO IDEA what s causing it  until it s too late

User · Answer

You can create your own coding guidelines  Just write a clear documentation for the rest of the team   Using  field helps the Intelilsense to filter all class variables just typing     I usually follow the Brad Adams Guidelines  but it recommends to not use underscore

User · Answer

It s just a convention some programmers use to make it clear when you re manipulating a member of the class or some other kind of variable  parameters  local to the function  etc   Another convention that s also in wide use for member variables is prefixing the name with  m     Anyway  these are only conventions and you will not find a single source for all of them  They re a matter of style and each programming team  project or company has their own  or even don t have any

User · Answer

The underscore is simply a convention  nothing more  As such  its use is always somewhat different to each person  Here s how I understand them for the two languages in question   In C    an underscore usually indicates a private member variable   In C   I usually see it used only when defining the underlying private member variable for a public property  Other private member variables would not have an underscore  This usage has largely gone to the wayside with the advent of automatic properties though   Before   private string  name  public string Name       get   return this  name        set   this  name   value        After   public string Name   get  set

User · Answer

Old question  new answer  C      Another use of underscores for C  is with ASP NET Core s DI  dependency injection   Private readonly variables of a class which got assigned to the injected interface during construction should start with an underscore  I guess it s a debate whether to use underscore for every private member of a class  although Microsoft itself follows it  but this one is certain    private readonly ILogger lt MyDependency gt   logger   public MyDependency ILogger lt MyDependency gt  logger         logger   logger

User · Answer

A naming convention like this is useful when you are reading code  particularly code that is not your own  A strong naming convention helps indicate where a particular member is defined  what kind of member it is  etc  Most development teams adopt a simple naming convention  and simply prefix member fields with an underscore   fieldName   In the past  I have used the following naming convention for C   which is based on Microsofts conventions for the  NET framework code  which can be seen with Reflector    Instance Field  m fieldName Static Field  s fieldName Public Protected Internal Member  PascalCasedName   Private Member  camelCasedName      This helps people understand the structure  use  accessibility and location of members when reading unfamiliar code very rapidly

User · Answer

There is a fully legit reason to use it in C   if the code must be extensible from VB NET as well   Otherwise  I would not    Since VB NET is is case insensitive  there is no simple way to access the protected field member in this code   public class CSharpClass       protected int field      public int Field   get   return field          E g  this will access the property getter  not the field   Public Class VBClass     Inherits CSharpClass      Function Test   As Integer         Return Field     End Function  End Class   Heck  I cannot even write field in lowercase -  VS 2010 just keeps correcting it   In order to make it easily accessible to derived classes in VB NET  one has to come up with another naming convention  Prefixing an underscore is probably the least intrusive and most  historically accepted  of them

User · Answer

With C   Microsoft Framework Design Guidelines suggest not using the underscore character for public members   For private members  underscores are OK to use   In fact  Jeffrey Richter  often cited in the guidelines  uses an m  for instance and a  s   for private static memberss    Personally  I use just   to mark my private members    m   and  s   verge on Hungarian notation which is not only frowned upon in  NET  but can be quite verbose and I find classes with many members difficult to do a quick eye scan alphabetically  imagine 10 variables all starting with m

User · Answer

Actually the  var convention comes from VB not C  or C    m      is another thing    This came to overcome the case insensitivity of VB when declaring Properties   For example  such code isn t possible in VB because it considers user and User as the same identifier  Private user As String  Public Property User As String   Get     Return user   End Get   Set ByVal Value As String      user   value   End Set End Property   So to overcome this  some used a convention to add     to the private field to come like this  Private  user As String  Public Property User As String   Get     Return  user   End Get   Set ByVal Value As String       user   value   End Set End Property   Since many conventions are for  Net and to keep some uniformity between C  et VB NET convention  they are using the same one   I found the reference for what I was saying   http   10rem net articles net-naming-conventions-and-programming-standards---best-practices     Camel Case with Leading Underscore  In   VB NET  always indicate  Protected  or    Private   do not use  Dim   Use of    m   is discouraged  as is use of a   variable name that differs from the   property by only case  especially with   protected variables as that violates   compliance  and will make your life a   pain if you program in VB NET  as you   would have to name your members   something different from the   accessor mutator properties  Of all   the items here  the leading underscore   is really the only controversial one    I personally prefer it over straight   underscore-less camel case for my   private variables so that I don t have   to qualify variable names with  this     to distinguish from parameters in   constructors or elsewhere where I   likely will have a naming collision    With VB NET s case insensitivity  this   is even more important as your   accessor properties will usually have   the same name as your private member   variables except for the underscore    As far as m  goes  it is really just   about aesthetics  I  and many others    find m  ugly  as it looks like there   is a hole in the variable name  It s   almost offensive  I used to use it in   VB6 all the time  but that was only   because variables could not have a   leading underscore  I couldn t be   happier to see it go away  Microsoft   recommends against the m   and the   straight    even though they did both   in their code  Also  prefixing with a   straight  m  is right out  Of course    since they code mainly in C   they can   have private members that differ only   in case from the properties  VB folks   have to do something else  Rather than   try and come up with   language-by-language special cases  I   recommend the leading underscore for   all languages that will support it  If   I want my class to be fully   CLS-compliant  I could leave off the   prefix on any C  protected member   variables  In practice  however  I   never worry about this as I keep all   potentially protected member variables   private  and supply protected   accessors and mutators instead  Why    In a nutshell  this convention is   simple  one character   easy to read    your eye is not distracted by other   leading characters   and successfully   avoids naming collisions with   procedure-level variables and   class-level properties class-level properties

User · Answer

I use the  var naming for member variables of my classes  There are 2 main reasons I do   1  It helps me keep track of class variables and local function variables when I m reading my code later   2  It helps in Intellisense  or other code-completion system  when I m looking for a class variable  Just knowing the first character is helpful in filtering through the list of available variables and methods

User · Answer

It s simply means that it s a member field in the class

User · Answer

From my experience  certainly limited   an underscore will indicate that it is a private member variable  As Gollum said  this will depend on the team  though

User · Answer

As far as the C and C   languages are concerned there is no special meaning to an underscore in the name  beginning  middle or end    It s just a valid variable name character    The  conventions  come from coding practices within a coding community   As already indicated by various examples above    in the beginning may mean private or protected members of a class in C     Let me just give some history that may be fun trivia   In UNIX if you have a core C library function and a kernel back-end where you want to expose the kernel function to user space as well the   is stuck in front of the function stub that calls the kernel function directly without doing anything else   The most famous and familiar example of this is exit   vs  exit   under BSD and SysV type kernels  There   exit   does user-space stuff before calling the kernel s exit service  whereas  exit just maps to the kernel s exit service   So   was used for  local  stuff in this case local being machine-local  Typically  functions   were not portable  In that you should not expect same behaviour across various platforms   Now as for   in variable names  such as   int  foo    Well psychologically  an   is an odd thing to have to type in the beginning  So if you want to create a variable name that would have a lesser chance of a clash with something else  ESPECIALLY when dealing with pre-processor substitutions you want consider uses of     My basic advice would be to always follow the convention of your coding community  so that you can collaborate more effectively

User · Answer

Many people like to have private fields prefixed with an underscore  It is just a naming convention   C  s  official  naming conventions prescribe simple lowercase names  no underscore  for private fields   I m not aware of standard conventions for C    although underscores are very widely used

User · Answer

var has no meaning and only serves the purpose of making it easier to distinguish that the variable is a private member variable   In C    using the  var convention is bad form  because there are rules governing the use of the underscore in front of an identifier   var is reserved as a global identifier  while  Var  underscore   capital letter  is reserved anytime  This is why in C    you ll see people using the var  convention instead

User · Answer

There s no particular single naming convention  but I ve seen that for private members

User · Answer

Now the notation using  this  as in this foobarbaz is acceptable for C  class member variables  It replaces the old  m   or just      notation  It does make the code more readable because there is no doubt what is being reference

[c#] Naming convention - underscore in C++ and C# variables

Examples related to c#

Examples related to c++

Examples related to naming-conventions