INFO: Microsoft Consulting Services Naming Conventions for Visual Basic

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Naming conventions help Visual Basic programmers:

• standardize the structure, coding style and logic of an application.
• create precise, readable, and unambiguous source code.
• be consistent with other language conventions (most importantly, the Visual Basic Programmers Guide and standard Windows C Hungarian notation).
• be efficient from a string size and labor standpoint, thus allowing a greater opportunity for longer and fuller object names.
• define the minimal requirements necessary to do the above.

Setting Environment Options

Use Option Explicit. Declare all variables to save programming time by reducing the number of bugs caused by typos (for example, aUserNameTmp vs. sUserNameTmp vs. sUserNameTemp). In the Environment Options dialog, set Require Variable Declaration to Yes. The Option Explicit statement requires you to declare all the variables in your Visual Basic program. Save Files as ASCII Text. Save form (.FRM) and module (.BAS) files as ASCII text to facilitate the use of version control systems and minimize the damage that can be caused by disk corruption. In addition, you can:

• use your own editor
• use automated tools, such as grep
• create code generation or CASE tools for Visual Basic
• perform external analysis of your Visual Basic code

To have Visual Basic always save files as ASCII text, from the Environment Options dialog, set the Default Save As Format option to Text.

Object Naming Conventions for Standard Objects

The following tables define the MCS standard object name prefixes. These prefixes are consistent with those documented in the Visual Basic Programmers Guide.

Prefix    Object Type                           Example
-------------------------------------------------------
ani       Animation button                      aniMailBox
bed       Pen Bedit                             bedFirstName
cbo       Combo box and drop down list box      cboEnglish
chk       Checkbox                              chkReadOnly
clp       Picture clip                          clpToolbar
cmd (3d)  Command button (3D)                   cmdOk (cmd3dOk)
com       Communications                        comFax
ctr       Control (when specific type unknown)  ctrCurrent
dat       Data control                          datBiblio
dir       Directory list box                    dirSource
dlg       Common dialog control                 dlgFileOpen
drv       Drive list box                        drvTarget
fil       File list box                         filSource
frm       Form                                  frmEntry
fra (3d)  Frame (3d)                            fraStyle (fra3dStyle)
gau       Gauge                                 gauStatus
gpb       Group push button                     gpbChannel
gra       Graph                                 graRevenue
grd       Grid                                  grdPrices
hed       Pen Hedit                             hedSignature
hsb       Horizontal scroll bar                 hsbVolume
img       Image                                 imgIcon
ink       Pen Ink                               inkMap
key       Keyboard key status                   keyCaps
lbl       Label                                 lblHelpMessage
lin       Line                                  linVertical
lst       List box                              lstPolicyCodes
mdi       MDI child form                        mdiNote
mpm       MAPI message                          mpmSentMessage
mps       MAPI session                          mpsSession
mci       MCI                                   mciVideo
mnu       Menu                                  mnuFileOpen
opt (3d)  Option Button (3d)                    optRed (opt3dRed)
ole       OLE control                           oleWorksheet
out       Outline control                       outOrgChart
pic       Picture                               picVGA
pnl3d     3d Panel                              pnl3d
rpt       Report control                        rptQtr1Earnings
shp       Shape controls                        shpCircle
spn       Spin control                          spnPages
txt       Text Box                              txtLastName
tmr       Timer                                 tmrAlarm
vsb       Vertical scroll bar                   vsbRate
				

Object Naming Convention for Database Objects

Prefix        Object Type          Example
------------------------------------------
db            ODBC Database        dbAccounts
ds            ODBC Dynaset object  dsSalesByRegion
fdc           Field collection     fdcCustomer
fd            Field object         fdAddress
ix            Index object         ixAge
ixc           Index collection     ixcNewAge
qd            QueryDef object      qdSalesByRegion
qry (suffix)  Query (see NOTE)     SalesByRegionQry
ss            Snapshot object      ssForecast
tb            Table object         tbCustomer
td            TableDef object      tdCustomers

				

NOTE: Using a suffix for queries allows each query to be sorted with its associated table in Microsoft Access dialogs (Add Table, List Tables Snapshot).

Menu Naming Conventions

Applications frequently use an abundance of menu controls. As a result, you need a different set of naming conventions for these controls. Menu control prefixes should be extended beyond the initial mnu label by adding an additional prefix for each level of nesting, with the final menu caption at the end of the name string. For example:

Menu Caption Sequence   Menu Handler Name
Help.Contents           mnuHelpContents
File.Open               mnuFileOpen
Format.Character        mnuFormatCharacter
File.Send.Fax           mnuFileSendFax
File.Send.Email         mnuFileSendEmail
				

When this convention is used, all members of a particular menu group are listed next to each other in the object drop-down list boxes (in the code window and property window). In addition, the menu control names clearly document the menu items to which they are attached.

Naming Conventions for Other Controls

For new controls not listed above, try to come up with a unique three character prefix. However, it is more important to be clear than to stick to three characters.

For derivative controls, such as an enhanced list box, extend the prefixes above so that there is no confusion over which control is really being used. A lower-case abbreviation for the manufacturer would also typically be added to the prefix. For example, a control instance created from the Visual Basic Professional 3D frame could uses a prefix of fra3d to avoid confusion over which control is really being used. A command button from MicroHelp could use cmdm to differentiate it from the standard command button (cmd).

Third-party Controls

Each third-party control used in an application should be listed in the application's overview comment section, providing the prefix used for the control, the full name of the control, and the name of the software vendor:

Prefix    Control Type        Vendor
cmdm      Command Button      MicroHelp
				

Variable and Routine Naming

Variable and function names have the following structure: <prefix><body><qualifier><suffix>

Part          Description                                  Example
--------------------------------------------------------------------------
<prefix>      Describes the use and scope of the variable. iGetRecordNext
<body>        Describes the variable.                      iGetNameFirst
<qualifier>   Denotes a derivative of the variable.        iGetNameLast
<suffix>      The optional Visual Basic type character.    iGetRecordNext%
				

Prefixes:

The following tables define variable and function name prefixes that are based on Hungarian C notation for Windows. These prefixes should be used with all variables and function names. Use of old Basic suffixes (such as %, &, #, etc.) are discouraged.

Variable and Function Name Prefixes:

Prefix    Converged    Variable Use         Data Type  Suffix
--------------------------------------------------------------------------
b         bln          Boolean              Integer    %
c         cur          Currency - 64 bits   Currency   @
d         dbl          Double - 64 bit      Double     #
                       signed quantity
dt        dat          Date and Time        Variant
e         err          Error
f         sng          Float/Single - 32    Single     !
                       bit signed
                       floating point
h                      Handle               Integer    %
i                      Index                Integer    %
l         lng          Long - 32 bit        Long       &
                       signed quantity
n         int          Number/Counter       Integer    %
s         str          String               String     $
u                      Unsigned - 16 bit    Long       &
                       unsigned quantity
          udt          User-defined type
vnt       vnt          Variant              Variant
a                      Array
				

NOTE: the values in the Converged column represent efforts to pull together the naming standards for Visual Basic, Visual Basic for Applications, and Access Basic. It is likely that these prefixes will become Microsoft standards at some point in the near future.

Scope and Usage Prefixes:

Prefix         Description
g              Global
m              Local to module or form
st             Static variable
(no prefix)    Non-static variable, prefix local to procedure
v              Variable passed by value (local to a routine)
r              Variable passed by reference (local to a routine)
				

Hungarian notation is as valuable in Visual Basic as it is in C. Although the Visual Basic type suffixes do indicate a variable's data type, they do not explain what a variable or function is used for, or how it can be accessed. Here are some examples: Each of these variable names tell a programmer something very different. This information is lost when the variable name is reduced to Send%. Scope prefixes such as g and m also help reduce the problem of name contention especially in multi-developer projects.

Hungarian notation is also widely used by Windows C programmers and constantly referenced in Microsoft product documentation and in industry programming books. Additionally, the bond between C programmers and programmers who use Visual Basic will become much stronger as the Visual C++ development system gains momentum. This transition will result in many Visual Basic programmers moving to C for the first time and many programmers moving frequently back and forth between both environments.

The Body of Variable and Routine Names

The body of a variable or routine name should use mixed case and should be as long as necessary to describe its purpose. In addition, function names should begin with a verb, such as InitNameArray or CloseDialog.

For frequently used or long terms, standard abbreviations are recommended to help keep name lengths reasonable. In general, variable names greater than 32 characters can be difficult to read on VGA displays.

When using abbreviations, make sure they are consistent throughout the entire application. Randomly switching between Cnt and Count within a project will lead to unnecessary confusion.

Qualifiers on Variable and Routine Names

Related variables and routines are often used to manage and manipulate a common object. In these cases, use standard qualifiers to label the derivative variables and routines. Although putting the qualifier after the body of the name might seem a little awkward (as in sGetNameFirst, sGetNameLast instead of sGetFirstName, sGetLastName), this practice will help order these names together in the Visual Basic editor routine lists, making the logic and structure of the application easier to understand. The following table defines common qualifiers and their standard meaning:

Qualifier  Description (follows Body)
--------------------------------------------------------------------------
First      First element of a set.
Last       Last element of a set.
Next       Next element in a set.
Prev       Previous element in a set.
Cur        Current element in a set.
Min        Minimum value in a set.
Max        Maximum value in a set.
Save       Used to preserve another variable that must be reset later.
Tmp        A "scratch" variable whose scope is highly localized within the
           code. The value of a Tmp variable is usually only valid across
           a set of contiguous statements within a single procedure.
Src        Source. Frequently used in comparison and transfer routines.
Dst        Destination. Often used in conjunction with Source.
				

User Defined Types

Declare user defined types in all caps with _TYPE appended to the end of the symbol name. For example:

Type CUSTOMER_TYPE
      sName As String
      sState As String * 2
      lID as Long
   End Type
				

When declaring an instance variable of a user defined type, add a prefix to the variable name to reference the type. For example:

   Dim custNew as CUSTOMER_TYPE
				

Naming Constants

The body of constant names should be UPPER_CASE with underscores (_) between words. Although standard Visual Basic constants do not include Hungarian information, prefixes like i, s, g, and m can be very useful in understanding the value and scope of a constant. For constant names, follow the same rules as variables. For Example:

<mnUSER_LIST_MAX   ' Max entry limit for User list (integer value,
                     ' local to module)
   gsNEW_LINE        ' New Line character string (global to entire
                     ' application)
				

Variant Data Type

If you know that a variable will always store data of a particular type, Visual Basic can handle that data more efficiently if you declare a variable of that type.

However, the variant data type can be extremely useful when working with databases, messages, DDE, or OLE. Many databases allow NULL as a valid value for a field. Your code needs to distinguish between NULL, 0 (zero), and "" (empty string). Many times, these types of operations can use a generic service routine that does not need to know the type of data it receives to process or pass on the data. For example:

   Sub ConvertNulls(rvntOrg As Variant, rvntSub As Variant)
      ' If rvntOrg = Null, replace the Null with rvntSub
      If IsNull(rvntOrg) Then rvntOrg = rvntSub
   End Sub
				

The are some drawbacks, however, to using variants. Code statements that use variants can sometimes be ambiguous to the programmer. For example:

   vnt1 = "10.01" : vnt2 = 11 : vnt3 = "11" : vnt4 = "x4"
   vntResult = vnt1 + vnt2  ' Does vntResult = 21.01 or 10.0111?
   vntResult = vnt2 + vnt1  ' Does vntResult = 21.01 or 1110.01?
   vntResult = vnt1 + vnt3  ' Does vntResult = 21.01 or 10.0111?
   vntResult = vnt3 + vnt1  ' Does vntResult = 21.01 or 1110.01?
   vntResult = vnt2 + vnt4  ' Does vntResult = 11x4 or ERROR?
   vntResult = vnt3 + vnt4  ' Does vntResult = 11x4 or ERROR?
				

The above examples would be much less ambiguous and easier to read, debug, and maintain if the Visual Basic type conversion routines were used instead. For Example:

   iVar1 = 5 + val(sVar2)   ' use this (explicit conversion)
   vntVar1 = 5 + vntVar2    ' not this (implicit conversion)
				

Commenting Your Code

All procedures and functions should begin with a brief comment describing the functional characteristics of the routine (what it does). This description should not describe the implementation details (how it does it) because these often change over time, resulting in unnecessary comment maintenance work, or worse yet, erroneous comments. The code itself and any necessary in-line or local comments will describe the implementation.

Parameters passed to a routine should be described when their functions are not obvious and when the routine expects the parameters to be in a specific range. Function return values and global variables that are changed by the routine (especially through reference parameters) must also be described at the beginning of each routine.

Routine header comment blocks should look like this (see the next section "Formatting Your Code" for an example):

Section    Comment Description
--------------------------------------------------------------------------
Purpose    What the routine does (not how).
Inputs     Each non-obvious parameter on a separate line with
           in-line comments
Assumes    List of each non-obvious external variable, control, open file,
           and so on.
Returns    Explanation of value returned for functions.
Effects    List of each effected external variable, control, file, and
           so on and the affect it has (only if this is not obvious)
				

Every non-trivial variable declaration should include an in-line comment describing the use of the variable being declared.

Variables, controls, and routines should be named clearly enough that in- line commenting is only needed for complex or non-intuitive implementation details.

An overview description of the application, enumerating primary data objects, routines, algorithms, dialogs, database and file system dependencies, and so on should be included at the start of the .BAS module that contains the project's Visual Basic generic constant declarations.

NOTE: The Project window inherently describes the list of files in a project, so this overview section only needs to provide information on the most important files and modules, or the files the Project window doesn't list, such as initialization (.INI) or database files.

Formatting Your Code

Because many programmers still use VGA displays, screen real estate must be conserved as much as possible, while still allowing code formatting to reflect logic structure and nesting.

Standard, tab-based, block nesting indentations should be two to four spaces. More than four spaces is unnecessary and can cause statements to be hidden or accidentally truncated. Less than two spaces does not sufficiently show logic nesting. In the Microsoft Knowledge Base, we use a three-space indent. Use the Environment Options dialog to set the default tab width.

The functional overview comment of a routine should be indented one space. The highest level statements that follow the overview comment should be indented one tab, with each nested block indented an additional tab. For example:

**************************************************************************
'Purpose:   Locate first occurrence of a specified user in UserList array.
'Inputs:    rasUserList():  the list of users to be searched
'           rsTargetUser:   the name of the user to search for
'Returns:   the index of the first occurrence of the rsTargetUser
'           in the rasUserList array. If target user not found, return -1.
'**************************************************************************

'VB3Line: Enter the following lines as one line
Function iFindUser (rasUserList() As String, rsTargetUser as String) _
   As Integer
   Dim i As Integer           ' loop counter
   Dim bFound As Integer      ' target found flag
   iFindUser = -1
   i = 0
   While i <= Ubound(rasUserList) and Not bFound
      If rasUserList(i) = rsTargetUser Then
         bFound = True
         iFindUser = i
      End If
   Wend
End Function
				

Variables and non-generic constants should be grouped by function rather than by being split off into isolated areas or special files. Visual Basic generic constants such as HOURGLASS should be grouped in a single module (VB_STD.BAS) to keep them separate from application-specific declarations.

Operators

Always use an ampersand (&) when concatenating strings, and use the plus sign (+) when working with numerical values. Using a plus sign (+) with non-numerical values, may cause problems when operating on two variants. For example:

   vntVar1 = "10.01"
   vntVar2 = 11
   vntResult = vntVar1 + vntVar2         ' vntResult =  21.01
   vntResult = vntVar1 & vntVar2         ' vntResult = 10.0111
				

Scope

Variables should always be defined with the smallest scope possible. Global variables can create enormously complex state machines and make the logic of an application extremely difficult to understand. Global variables also make the reuse and maintenance of your code much more difficult. Variables in Visual Basic can have the following scope:

Scope             Variable Declared In:            Visibility
--------------------------------------------------------------------------
Procedure-level   Event procedure, sub, or         Visible in the
                  function                         procedure in which
                                                   it is declared
Form-level,       Declarations section of a form   Visible in every
Module-level      or code module (.FRM, .BAS)      procedure in the
                                                   form or code
                                                   module
Global            Declarations section of a code   Always visible
                  module (.BAS, using Global
                  keyword)
				

In a Visual Basic application, only use global variables when there is no other convenient way to share data between forms. You may want to consider storing information in a control's Tag property, which can be accessed globally using the form.object.property syntax.

If you must use global variables, it is good practice to declare all of them in a single module and group them by function. Give the module a meaningful name that indicates its purpose, such as GLOBAL.BAS.

With the exception of global variables (which should not be passed), procedures and functions should only operate on objects that are passed to them. Global variables that are used in routines should be identified in the general comment area at the beginning of the routine. In addition, pass arguments to subs and functions using ByVal, unless you explicitly want to change the value of the passed argument.

Write modular code whenever possible. For example, if your application displays a dialog box, put all the controls and code required to perform the dialog's task in a single form. This helps to keep the application's code organized into useful components and minimizes its runtime overhead.

Third-party Controls

NOTE: The products discussed below are manufactured by vendors independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding these products' performance or reliability.

The following table lists standard third-party vendor name prefix characters to be used with control prefixes:

Vendor               Abbv
-------------------------

MicroHelp (VBTools)  m
Pioneer Software     p
Crescent Software    c
Sheridan Software    s
Other (Misc)         o
				

The following table lists standard third-party control prefixes:

Control         Control     Abbr  Vendor     Example            VBX File
Type            Name                                            Name
--------------------------------------------------------------------------
Alarm           Alarm       almm  MicroHelp  almmAlarm          MHTI200.VBX
Animate         Animate     anim  MicroHelp  animAnimate        MHTI200.VBX
Callback        Callback    calm  MicroHelp  calmCallback       MHAD200.VBX
Combo Box       DB_Combo    cbop  Pioneer    cbopComboBox       QEVBDBF.VBX
Combo Box       SSCombo     cbos  Sheridan   cbosComboBox       SS3D2.VBX
Check Box       DB_Check    chkp  Pioneer    chkpCheckBox       QEVBDBF.VBX
Chart           Chart       chtm  MicroHelp  chtmChart          MHGR200.VBX
Clock           Clock       clkm  MicroHelp  clkmClock          MHTI200.VBX
Button          Command     cmdm  MicroHelp  cmdmCommandButton  MHEN200.VBX
                Button
Button          DB_Command  cmdp  Pioneer    cmdpCommandButton  QEVBDBF.VBX
Button (Group)  Command     cmgm  MicroHelp  cmgmBtton          MHGR200.VBX
                Button
                (multiple)
Button          Command     cmim  MicroHelp  cmimCommandButton  MHEN200.VBX
                Button
                (icon)
CardDeck        CardDeck    crdm  MicroHelp  crdmCard           MHGR200.VBX
Dice            Dice        dicm  MicroHelp  dicmDice           MHGR200.VBX
List Box (Dir)  SSDir       dirs  Sheridan   dirsDirList        SS3D2.VBX
List Box (Drv)  SSDrive     drvs  Sheridan   drvsDriveList      SS3D2.VBX
List Box (File) File List   film  MicroHelp  filmFileList       MHEN200.VBX
List Box (File) SSFile      fils  Sheridan   filsFileList       SS3D2.VBX
Flip            Flip        flpm  MicroHelp  flpmButton         MHEN200.VBX
Scroll Bar      Form Scroll fsrm  MicroHelp  fsrmFormScroll     ???
Gauge           Gauge       gagm  MicroHelp  gagmGauge          MHGR200.VBX
Graph           Graph       gpho  Other      gphoGraph          XYGRAPH.VBX
Grid            Q_Grid      grdp  Pioneer    grdpGrid           QEVBDBF.VBX
Scroll Bar      Horizontal  hsbm  MicroHelp  hsbmScroll         MHEN200.VBX
                Scroll Bar
Scroll Bar      DB_HScroll  hsbp  Pioneer    hsbpScroll         QEVBDBF.VBX
Graph           Histo       hstm  MicroHelp  hstmHistograph     MHGR200.VBX
Invisible       Invisible   invm  MicroHelp  invmInvisible      MHGR200.VBX
List Box        Icon Tag    itgm  MicroHelp  itgmListBox        MHAD200.VBX
Key State       Key State   kstm  MicroHelp  kstmKeyState       MHTI200.VBX
Label           Label (3d)  lblm  MicroHelp  lblmLabel          MHEN200.VBX
Line            Line        linm  MicroHelp  linmLine           MHGR200.VBX
List Box        DB_List     lstp  Pioneer    lstpListBox        QEVBDBF.VBX
List Box        SSList      lsts  Sheridan   lstsListBox        SS3D2.VBX
MDI Child       MDI Control mdcm  MicroHelp  mdcmMDIChild       ???
Menu            SSMenu      mnus  Sheridan   mnusMenu           SS3D3.VBX
Marque          Marque      mrqm  MicroHelp  mrqmMarque         MHTI200.VB
Picture         OddPic      odpm  MicroHelp  odpmPicture        MHGR200.VBX
Picture         Picture     picm  MicroHelp  picmPicture        MHGR200.VBX
Picture         DB_Picture  picp  Pioneer    picpPicture        QEVBDBF.VBX
Property Vwr    Property    pvrm  MicroHelp  pvrmPropertyViewer MHPR200.VBX
                Viewer
Option (Group)  DB_RadioGroup radp Pioneer   radqRadioGroup     QEVBDBF.VBX
Slider          Slider      sldm  MicroHelp  sldmSlider         MHGR200.VBX
Button (Spin)   Spinner     spnm  MicroHelp  spnmSpinner        MHEN200.VBX
Spreadsheet     Spreadsheet sprm  MicroHelp  sprmSpreadsheet    MHAD200.VBX
Picture         Stretcher   strm  MicroHelp  strmStretcher      MHAD200.VBX
Screen Saver    Screen Saver svrm MicroHelp  svrmSaver          MHTI200.VBX
Switcher        Switcher    swtm  MicroHelp  swtmSwitcher       ???
List Box        Tag         tagm  MicroHelp  tagmListBox        MHEN200.VBX
Timer           Timer       tmrm  MicroHelp  tmrmTimer          MHTI200.VBX
ToolBar         ToolBar     tolm  MicroHelp  tolmToolBar        MHAD200.VBX
List Box        Tree        trem  MicroHelp  tremTree           MHEN200.VBX
Input Box       Input (Text) txtm MicroHelp  inpmText           MHEN200.VBX
Input Box       DB_Text     txtp  Pioneer    txtpText           QEVBDBF.VBX
Scroll Bar      Vertical    vsbm  MicroHelp  vsbmScroll         MHEN200.VBX
                Scroll Bar
Scroll Bar      DB_VScroll  vsbp  Pioneer    vsbpScroll         QEVBDBF.VBX