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Constants with & prefix and variables with % trailer

Posted on 2004-04-23
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Last Modified: 2010-05-02
Hi,

As I'm broadening my VB knowledge, I came across things like this a couple of times:
Private Const GENERIC_READ = &H80000000

this is usually used with API calls it seems


and things like this:
For i%=0 to 100
    Array(i%) = "Lipsum"
Next i%


Now I suppose the first has something to do with hexadecimals. Just a wild guess, but I'd like to know more about that.
The second one is a puzzler. I used it a couple of times myself, to dynamically create control arrays, but what it means... You got me.
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Question by:boeman
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6 Comments
 
LVL 11

Expert Comment

by:jmwheeler
ID: 10899002
You got it.  &H is for hexadecimal.  The % I believe is for long integer's.
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LVL 43

Assisted Solution

by:TimCottee
TimCottee earned 1000 total points
ID: 10899067
Hi boeman,

&H is hex

Suffixes:
& is long integer
% is integer
$ is string
! is single
# is double

There may be some others but these are the most common.

They are not necessarily required when you explicitly declare a variable but can come in handy when you need to ensure that a specific datatype is used:

Msgbox 32000 + 5000
For example will generate an overflow error because the result of adding these two implicit integers together is larger than the integer datatype can handle.

Msgbox 32000& + 5000
will not because one of them is a long and therefore the result is implicitly cast to a long.

Tim Cottee
Brainbench MVP for Visual Basic
http://www.brainbench.com
0
 
LVL 6

Expert Comment

by:mmusante
ID: 10899076
% is for Integer
& is for Long
$ is for string
# is for Double
! is for single
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LVL 3

Author Comment

by:boeman
ID: 10899236
Thanks TimCottee, that part of the question is clear for me now.

jmwheeler: for the &H, &D etc, it stands for hexadecimal and decimal etc.. But I need some kind of explanation or a nice example.

Tim is going to be rewarded with half of the points for trailing sings.
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LVL 43

Accepted Solution

by:
TimCottee earned 1000 total points
ID: 10899391
boeman,

This is one of those questions where perhaps there is no definitive answer. I guess the closest I could offer is this:

& as suffix represents a long integer so & as a prefix also signifies a long integer but the next letter (H, O, D) identifies the base in which the following "number" is represented.

9 &O11 &H9
15 &O17 &HF
16 &O20 &H10
20 &O24 &H14
255 &O377 &HFF

Show the same numbers in decimal, octal and hexadecimal representations. I have never used or seen any code examples using Octal but the functionality is there!

Tim.
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LVL 3

Author Comment

by:boeman
ID: 10900129
OK, thanks for rectifying this issue.
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