What does DIM stand for in Visual Basic and BASIC

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What does DIM stand for in Visual Basic

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Back in the day DIM reserved memory for the array and when memory was limited you had to be careful how you used it   I once wrote  in 1981  a BASIC program on TRS-80 Model III with 48Kb RAM   It wouldn t run on a similar machine with 16Kb RAM until I decreased the array size by changing the DIM statement

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Dim originally  in BASIC  stood for Dimension  as it was used to define the dimensions of an array   The original implementation of BASIC was Dartmouth BASIC  which descended from FORTRAN  where DIMENSION is spelled out   Nowadays  Dim is used to define any variable  not just arrays  so its meaning is not intuitive anymore

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Dim have had different meanings attributed to it   I ve found references about Dim meaning  Declare In Memory   the more relevant reference is a document on Dim Statement published Oracle as part of the Siebel VB Language Reference  Of course  you may argue that if you do not declare the variables in memory where do you do it  Maybe  Declare in Module  is a good alternative considering how Dim is used   In my opinion   Declare In Memory  is actually a mnemonic  created to make easier to learn how to use Dim  I see  Declare in Memory  as a better meaning as it describes what it does in current versions of the language  but it is not the proper meaning   In fact  at the origins of Basic Dim was only used to declare arrays  For regular variables no keyword was used  instead their type was inferred from their name  For instance  if the name of the variable ends with   then it is a string  this is something that you could see even in method names up to VB6  for example Mid    And so  you used Dim only to give dimension to the arrays  notice that ReDim resizes arrays      Really  Does It Matter  I mean  it is a keyword it has its meaning inside an artificial language  It doesn t have to be a word in English or any other natural language  So it could just mean whatever you want  all that matters is that it works   Anyhow  that is not completely true  As BASIC is part of our culture  and understanding why it came to be as it is - I hope - will help improve our vision of the world     I sit in from of my computer with a desire to help preserve this little piece of our culture that seems lost  replaced by our guessing of what it was  And so  I have dug MSDN both current and the old CDs from the 1998 version  I have also searched the documention for the old QBasic  Had to use DOSBox  and managed to get some Darthmouth manual  all to find how they talk about Dim  For my disappointment  they don t say what does Dim stand for  and only say how it is used   But before my hope was dim  I managed to find this BBC Microcomputer System Used Guide  that claims to be from 1984  and I don t want to doubt it   The BBC Microcomputer used a variant of BASIC called BBC BASIC and it is described in the document  Even though  it doesn t say what does Dim stand for  it says  on page 104           you can dimension N  to have as many entries as you want  For   example  DIM N  1000  would create a string array with space for 1000   different names    As I said  it doesn t say that Dim stands for dimension  but serves as proof to show that associating Dim with Dimension was a common thing at the time of writing that document   Now  I got a rewarding surprise later on  at page 208   the title for the section that describes the DIM keyword  note  that is not listed in the contents  says      DIM dimension of an array   So  I didn t get the quote  Dim stands for     but I guess it is clear that any decent human being that is able to read those document will consider that Dim means dimension     With renewed hope  I decided to search about how Dim was chosen  Again  I didn t find an account on the subject  still I was able to find a definitive quote      Before you can use an array  you must define it in a DIM  dimension  statement    You can find this as part of the True BASIC Online User s Guides at the web page of True BASIC inc  a company founded by Thomas Eugene Kurtz  co-author of BASIC     So  In reallity  Dim is a shorthand for DIMENSION  and yes  That existed in FORTRAN before  so it is likely that it was picked by influence of FORTRAN as Patrick McDonald said in his answer     Dim sum as string    this is not a chinese meal  REM example usage in VB NET

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DIM stands for Declaration In Memory  DIM x As New Integer  creates a space in memory where the variable x is stored

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The Dim keyword is optional  when we are using it with  modifiers- Public  Protected  Friend  Protected Friend Private Shared Shadows Static ReadOnly etc  e g  - Static nTotal As Integer  For reference type  we have to use new keyword to create the  new instance of the class or structure   e g  Dim lblTop As New System Windows Forms Label   Dim statement can be used with out a datatype when you set  Option Infer to On  In that case the compiler infers the data type of a variable from the type of its initialization expression   Example     Option Infer On  Module SampleMod  Sub Main     Dim nExpVar   5   The above statement is equivalent to-  Dim nExpVar As Integer

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Dimension a variable  basically you are telling the compiler that you are going to need a variable of this type at some point

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It s short for Dimension  as it was originally used in BASIC to specify the size of arrays      DIM      short for dimension  define the size of arrays   Ref  http   en wikipedia org wiki Dartmouth BASIC  A part of the original BASIC compiler source code  where it would jump when finding a DIM command  in which you can clearly see the original intention for the keyword   DIM    LDA XR01             BACK OFF OBJECT POINTER        SUB N3        STA RX01        LDA L        2       GET VARIABLE TO BE DIMENSIONED        STA 3        LDA S        3        CAB N36              CHECK FOR   ARRAY        BRU   7              NOT                Ref  http   dtss dartmouth edu scans BASIC BASIC 20Compiler pdf  Later on it came to be used to declare all kinds of variables  when the possibility to specify the type for variables was added in more recent implementations

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Short for Dimension  It s a type of variable  You declare  or  tell  Visual Basic  that you are setting up a variable with this word

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It stands for Dimension  but is generally read as  Create Variable   or  Allocate Space for This

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Variable declaration  Initially  it was short for  dimension   which is not a term that is used in programming  outside of this specific keyword  to any significant degree   http   in answers yahoo com question index qid 20090310095555AANmiAZ

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