DOCUMENT:Q306826  10-SEP-2001  [vbwin]
TITLE   :HOWTO: Get and Set the Memory Settings with eVB
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER::3.0
OPER/SYS:
KEYWORDS:kbVBM300

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The information in this article applies to:

 - Microsoft eMbedded Visual Basic, version 3.0 
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SUMMARY
=======

This article demonstrates how to use an eMbedded Visual Basic (eVB) application
to adjust the system memory division.

MORE INFORMATION
================

On Microsoft Windows CE devices, you can adjust the memory settings to allocate
memory between object store (storage) and program memory. This adjustment is
typically made in the system's Control Panel. The sample code to follow
illustrates how you can use the SetSystemMemoryDivision function to
programmatically set this boundary line.

Step-by-Step Example
--------------------

1. Start a new PocketPC project in eVB. Form1 is created by default.

2. Add six labels, two text boxes, two command buttons, one horizontal scroll
   bar, and one shape control to Form1. Do not be concerned with the placement
   of these controls.

3. Paste the following code into Form1:

   Option Explicit
   Const SYSMEM_CHANGED = 0
   Const SYSMEM_FAILED = 3

   Declare Function GetLastError Lib "coredll" () As Long

   Declare Function GetSystemMemoryDivision Lib "coredll" _
       (lpdwStorePages As Long, _
        lpdwRamPages As Long, _
        lpdwPageSize As Long) As Long

   Declare Function SetSystemMemoryDivision Lib "coredll" _
       (ByVal dwStorePages As Long) As Long

   Dim lStorePages As Long
   Dim lPageSize As Long
   Dim lRamPages As Long
       
   Private Sub GetMemoryInfo()
       Dim lRet As Long
       lRet = GetSystemMemoryDivision(lStorePages, lRamPages, lPageSize)
       If lRet > 0 Then
           SetUI
       Else
           MsgBox "Call failed"
       End If
   End Sub

   Private Sub Command1_Click()
       GetMemoryInfo
   End Sub

   Private Sub Command2_Click()
       Dim lRet As Long
       lRet = SetSystemMemoryDivision(lStorePages)
       
       If lRet = SYSMEM_FAILED Then
           MsgBox "Failure....GetLastError returned: " & GetLastError
       End If
       
       GetMemoryInfo
   End Sub

   Private Sub Form_OKClick()
       App.End
   End Sub

   Sub SetUI()
       HScroll1.Max = lStorePages + lRamPages
       HScroll1.Value = lStorePages
       Label4.Caption = "Total main memory: " & _
           FormatNumber(TurntoMB(lStorePages + lRamPages)) & " MB"
       Text1.Text = FormatNumber(TurntoMB(lStorePages), 2) & " MB"
       Text2.Text = FormatNumber(TurntoMB(lRamPages), 2) & " MB"
       Label5.Caption = Text1.Text
       Label6.Caption = Text2.Text
   End Sub

   Public Function TurntoMB(lsize As Long) As Long
       TurntoMB = (lsize * lPageSize) / 1024 ^ 2
   End Function

   Public Function TurnToMem(lsize As Long) As Long
       TurnToMem = (lsize / lPageSize) * 1024 ^ 2
   End Function

   Private Sub HScroll1_Change()
       Text1.Text = FormatNumber(TurntoMB(HScroll1.Value), 2) & " MB"
       Text2.Text = FormatNumber(TurntoMB(HScroll1.Max - _
           HScroll1.Value), 2) & " MB"
       lStorePages = HScroll1.Value
   End Sub

   Private Sub Form_Load()
       Label1.Caption = "Storage"
       Label2.Caption = "Program"
       Label3.Caption = "Allocated"
       Label4.Caption = ""
       Label5.Caption = ""
       Label6.Caption = ""
       Text1.Text = ""
       Text2.Text = ""
       Form1.Caption = "Memory Division"
       Command1.Caption = "Get Memory Info"
       Command2.Caption = "Set Memory Info"
       HScroll1.Min = 0
       HScroll1.Max = 8000
       HScroll1.LargeChange = 100
       HScroll1.SmallChange = 10
       Label1.Move 120, 480, 735, 255
       Label2.Move 2400, 480, 735, 255
       Label3.Move 1320, 1680, 855, 255
       Label4.Move 120, 120, 2895, 255
       Label5.Move 240, 1680, 975, 255
       Label6.Move 2280, 1680, 975, 255
       Text1.Move 120, 840, 975, 255
       Text2.Move 2400, 840, 975, 255
       Command1.Move 120, 2520, 2055, 375
       Command2.Move 120, 3000, 2055, 375
       HScroll1.Move 120, 1200, 3255, 255
       Shape1.Move 120, 1560, 3255, 495

       GetMemoryInfo
   End Sub

4. Ensure that the remote device is being targeted, and run the application.

5. Scroll the horizontal scroll bar, and click Set Memory Info to change the
   memory settings.

IMPORTANT: A PocketPC runs a memory division check at least once every 5 seconds
and whenever the Task Manager starts an application. As a part of this check,
the memory division is set to equal parts if it is determined that free memory
in one division is 5 times larger than the free memory in the other.

REFERENCES
==========

For more information about Windows CE memory architecture, see the following
MSDN Web site:

   http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wcekern/htm/prog_mem.asp

Additional query words:

======================================================================
Keywords          : kbVBM300 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword2 kbVBeMbSearch kbVBeMb300
Version           : :3.0
Issue type        : kbhowto

=============================================================================

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