Memory occupied by a constant

[Crirus]

If I declare a constant like
Public Const myConst as Byte =1

or I declare

Public Const myConst = 1
there is any difference?

--
Ceers,
Crirus

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If work were a good thing, the boss would take it all from you

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[Herfried K. Wagner [MVP]]

* "Crirus" <Cr****@datagroup.ro> scripsit:

If I declare a constant like
Public Const myConst as Byte =1

or I declare

Public Const myConst = 1
there is any difference?

The 2nd constant will be stored as 'Int32'.

--
Herfried K. Wagner
MVP · VB Classic, VB.NET
<http://www.mvps.org/dotnet>

<http://www.plig.net/nnq/nquote.html>

[Crirus]

OK... I'm just wandering why dont they store the const in minimum space
required it that const is unchangeable any way once declared

--
Ceers,
Crirus

------------------------------
If work were a good thing, the boss would take it all from you

------------------------------

"Crirus" <Cr****@datagroup.ro> wrote in message
news:Ok****************@TK2MSFTNGP11.phx.gbl...

If I declare a constant like
Public Const myConst as Byte =1

or I declare

Public Const myConst = 1
there is any difference?

--
Ceers,
Crirus

------------------------------
If work were a good thing, the boss would take it all from you

------------------------------

[Fergus Cooney]

Hi Crirus,

Minimum space storage is a bit of a myth. A single byte value may take
up 1, 2 or 4 bytes depending on how values are aligned and what other values
it is with. If you want control over these things you have to specify
packing attributes. Mostly, of course, we leave it to the compiler and rely
on multi-MBs of memory making it immaterial.

In the case of the Const, it won't be minimised but will be given the
default type, in this case Int32. It is assumed that if a Byte is required
then a Byte will be specified. The majority of constants are probably ints
and in the code, any byte assigned to an int variable or using in an int
expression will have to be expanded to an int first. So, you could save a
byte or two in storage of the constant but spend both bytes and time
converting it when actually using it.

Regards,
Fergus

[Crirus]

That's right I just was curious about that

--
Ceers,
Crirus

------------------------------
If work were a good thing, the boss would take it all from you

------------------------------

"Fergus Cooney" <fi****@post.com> wrote in message
news:u%****************@TK2MSFTNGP12.phx.gbl...

Hi Crirus,

Minimum space storage is a bit of a myth. A single byte value may take
up 1, 2 or 4 bytes depending on how values are aligned and what other values it is with. If you want control over these things you have to specify
packing attributes. Mostly, of course, we leave it to the compiler and rely on multi-MBs of memory making it immaterial.

In the case of the Const, it won't be minimised but will be given the
default type, in this case Int32. It is assumed that if a Byte is required
then a Byte will be specified. The majority of constants are probably ints
and in the code, any byte assigned to an int variable or using in an int
expression will have to be expanded to an int first. So, you could save a
byte or two in storage of the constant but spend both bytes and time
converting it when actually using it.

Regards,
Fergus

[Jay B. Harlow [MVP - Outlook]]

Crirus,
In addition to Fergus & Herfried's comments, remember a constant doesn't
really occupy any space as a variable would, the value itself is used in the
IL instructions when ever it is referenced.

To expand on Fergus's comments:

Public Const myByte As Byte = 1
Public Const myInteger As Integer = 1

Produce the same IL code when used, the 'size' (Byte verses Integer) is used
by the compiler to allow or disallow values on the constant itself.
Interesting enough both of the above can be assigned to a Byte variable!

Dim i As Byte = myByte
IL_0001: ldc.i4.1
IL_0002: stloc.2

Dim j As Integer = myInteger
IL_0003: ldc.i4.2
IL_0004: stloc.3

The "ldc" instruction is load constant, the ".i4" says Int32, the ".1" says
load the value 1. The "stloc" is the store location instruction, the ".2" &
".3" are location 2 & location 3 which is the third & fourth variable in
this routine (variable locations start with zero).

Public Const myConst = 1 This causes a compile error if you are using Option Strict On.

Hope this helps
Jay

"Crirus" <Cr****@datagroup.ro> wrote in message
news:Ok****************@TK2MSFTNGP11.phx.gbl... If I declare a constant like
Public Const myConst as Byte =1

or I declare

Public Const myConst = 1
there is any difference?

--
Ceers,
Crirus

------------------------------
If work were a good thing, the boss would take it all from you

------------------------------