The origin of the "DIM" keyword

RGCook · December 26th, 2003, 05:23 PM

OK, this is for beginners so I have a somewhat of a strange question. Regarding the DIM keyword, I have read that it is short for Dimension, as in making space for a variable in memory (as described on page 46 of the Beginning VB.NET 2nd Edition book). Also, I have read that it is short for the phrase "Declare In Memory".

I am curious which is correct or if we will ever know for sure.

Like I said, I am just curious, this is not critical stuff but does anyone know for sure?!?!

JonathanC · January 3rd, 2004, 08:03 PM

I believe that its from Dimension

Jonathan Crossland
http://www.jonathancrossland.com

Akuta · February 10th, 2004, 02:07 PM

Yes, Dim originated from the word "Dimension" as it "dimensions" memory for the object.

srivaniannapurna.solasa · February 4th, 2009, 06:55 AM

Quote:

Originally Posted by RGCook

OK, this is for beginners so I have a somewhat of a strange question. Regarding the DIM keyword, I have read that it is short for Dimension, as in making space for a variable in memory (as described on page 46 of the Beginning VB.NET 2nd Edition book). Also, I have read that it is short for the phrase "Declare In Memory".

I am curious which is correct or if we will ever know for sure.

Like I said, I am just curious, this is not critical stuff but does anyone know for sure?!?!

thanq!!! for giving this data

Thearon · February 4th, 2009, 09:18 AM

I've always understood it to mean dimension. Of course you can check the Wikipedia (http://en.wikipedia.org/wiki/Main_Page) and you'll probably get more information than you want to know.

Old Pedant · February 4th, 2009, 05:05 PM

As one who was writing BASIC interpreters from 1973 through 1986, I can positively affirm that indeed it is short for DIMension. Just like REM is short for REMark. (I think that's still allowed even in VB.NET, for compatibility with ancient history.)

The original Dartmouth BASIC (yes, that's where the language came from...and did you know BASIC is an acronym? Beginner's All-purpose Symbolic Instruction Code. Want to bet that the name came before the acronym? I'll take the bet and give you odds) allowed only two kinds of names: A,B,C,A1,A2,...A9,B1,B2,...B9,...Z9 were all numbers. No distinction between integers and floating point. All math was done in floating point. And then A$,B$, C$, A1$,...Z9$ were all strings. You never had to DIM a standard variable (not even sure it was legal) because the name of course implied the type. You only used DIM to create arrays, and hence you declared the DIMension of the array.

As late as the 1980s, this kind of syntax was still the standard. The variable name implied the data type. By then, most BASICs had extended the names to many characters and the number of data types by adding different extensions. e.g., Value# was a floating point number, Index% was an integer, etc. I dunno if Visual BASIC [and yes, BASIC should always be capitalized, since it is (hah!) an acronym] was the first to start allowing DIM to specify a data type, as opposed to just an array size, or not. But certainly VB is the language that made this usage of DIM the standard.

********************

p.s.: Yep, I just checked in Visual Studio and not only is REM still accepted as equivalent to the ' for starting a comment, it's even recognized as soon as you type REM by turning to the comment coloring. (Note that if you use it on the end of a line, you have to precede it with a colon, as in

Code:

Dim foo As Integer : REM counts how many widgets we have

Now...anybody want a history of how strings were DIMensioned and the two rival factions and who won? <grin/>

p.p.s.: And who needs Wikipedia when you have a living fossil sitting right here? <grin style="sheepish" />

alliancejhall · February 4th, 2009, 09:28 PM

Bill you are truly a wealth (or is i well) of knowledge. Thanks for that complete history/definition. I for one learned quite a bit!

Old Pedant · February 5th, 2009, 08:24 PM

Hey, guess what!

In answering another question, I had occasion to refer to the official "Microsoft Visual Basic .NET Language Specification", version 7.1, by Paul Vick.

And VB.NET *STILL* supports those magic suffix characters that predetermine the datatype!!!

Apparently, in fact, if you use those suffix characters then you don't even NEED to use a type name. Even when OPTION STRICT is on!

Hang on...let me check that...

YES!!!!

First of all, make sure you are compiling with OPTION STRICT ON (or use <%@ Strict="true" %> if building an ASP.NET page, for example).

Now add the code line:

Code:

Dim s = "test"

You will get a message like this:
Option Strict On requires all variable declarations to have an 'As' clause.

Okay, now change that to

Code:

Dim s$ = "test"

and rebuild. PRESTO! No error message!!!!!!!

Or try this

Code:

Dim s# = "test"

and receive the message "Option Strict On disallows implicit conversion from String to Double".

VOILA!

The complete list of "type character" suffixes supported in VB.NET is impressive:

Code:

%  == Integer
&  == Long [remember, in VB.NET, Long means 64 bits]
@  == Decimal
!  == Single [floating point, only 6 digits of accuracy...no point in ever using this]
#  == Double [floating point, 15+ digits of accuracy]
$  == String [as we've already seen]

In other words
    Dim somename% 
is IDENTICAL (in effect) to doing
    Dim somename AS Integer
except you must continue to use the name somename%

So... Nothing worth carrying around with you. Just interesting trivia and nostalgia and compatibility with bygone languages.

dinesh · February 6th, 2009, 09:01 AM

hi old pedant, very interesting to read your posts. waiting for more from u.

dinesh · February 6th, 2009, 09:03 AM

Quote:

Originally Posted by srivaniannapurna.solasa

thanq!!! for giving this data

hi srivanianapoorna r u from tamilnadu...