The document discusses dynamic link libraries (DLLs) and how they can be used to create modular programs in Visual C++. It provides details on how DLLs export functions, how client programs import those functions, and how Windows locates DLLs at runtime. It also discusses how to create regular and extension DLLs using MFC and how to build a client program that loads and calls a DLL. Finally, it covers using ODBC and MFC classes like CRecordSet to connect to and manipulate a database from a Visual C++ application.

1. VISUAL PROGRAMMING

2. DYNAMIC LINK LIBRARY(DLL)
 To write modular software.
 Classes are Build-Time Modular, DLLs are
Runtime Modular.
 Build smaller DLL modules and test them
individually.
 For example, put a c++ class in DLL, which might
be as small as 12kb after compiling and linking.
Client prg can load and link your DLL very quickly
when they run.
 Microsoft Windows itself uses DLLs for its major
function.

3. How Import Are Matched to
Export
 A DLL contains a table of exported function.
 The function table also contains the addresses of the
functions within the DLL.
 One EXE file an import functions from one or more
DLLs.
 DLLs call inside other DLLs.
 DLL can have both import and export.
 In the DLL code, explicitly declare the exported
functions like this:
 _declspec(dllexport)int MyFunction(int n);
 On client side, declare the corresponding imports like
this:
 _declspec(dllimport)int MyFunction(int n);

4. How the Client program finds a DLL
 If linked explicitly with LoadLibrary(), the DLLs can
be specified in full pathname. If not, or if linked
implicitly, windows follows this search sequence to
locate your DLL.
 1.The directory containing the EXE file.
 2. The process’s current directory.
 3. The Windows system directory.
 4. The Windows directory.
 5. The directories listed in the path environment
variable.
 Built a DLL, and run DLL from client program.

5. MFC DLLs
 AppWizard allows building two kinds of DLLs
with MFC library support.
 Extension DLLs.
 Regular DLLs.

6. Extension DLL
 It supports a C++ interface.
 The DLL can export whole classes, hence the
client can construct objects of those classes or
derive classes from them.
 It dynamically links to the code in the DLL version
of the MFC library. Hence it requires that the client
program be dynamically linked to MFC library.
 Both the client program and the extension DLL be
synchronized to the same version of the MFC
DLLs.
 This type of DLLs are quite small, size 10kb,
which loads quickly.

7. Regular DLL
 If there is a need for DLL that can be loaded bt
any win32 programming environment, use a
regular DLL.
 A big restriction here is that the regular DLL
can export only C-style functions.
 It can’t export C++ classes, member function,
or overloaded functions because every C++
compiler has its own method of decorating
names.
 Use C++ classes inside the regular DLL.
 To build this type of DLL, it can choose to
statically link or dynamically link to the MFC

8. Example for creating a regular DLL for
calculating the square root and use it in the
project
 Create a new application by selecting file-
>new->project
 Select MFC Appwizard(dll).
 Project name: ex1
 Press ok button.
 In AppWizard
 Application type: Regular DLL using Shared MFC.
 Select finished button.
 The form screen will appear.

9.  Add the code for the square root function in the
ex1.cpp file.
Extern “C” _declspec(dllexport)double
squareroot(double d)
{
If (d>=0.0)
return sqrt(d);
AfxMessageBox(“can not square root”);
return 0.0
}
include math.h in the file containing this code.
Built the project.

10. Testing DLL: Client Program
 Create a new application by selecting file-
>new->project
 Select MFC Appwizard(exe).
 Project name: ex2
 Press ok button.
 In AppWizard
 Application type: Dialog based
 Select finished button.
 The Dialog window will appear.

11.  Add 2 static boxes, 2 Edit box and 1 button to form
window.
 Code the OnCompute function to call the DLL’s
exported function
Void Cex2Dialog::OnCompute()
{
UpdateDate(true);
m_dOutput=squareroot(m_dInput);
UpdateData(false);
}
 Declare this squareroot function as an imported
function.
 Add the following line to ex2Dialog.h file
 .extern “C” _declspec(dllimport)double squareroot(double
d);

12.  Select project->setting from vc++ and copy the
link where u saved dll file (i.e) ex1.lib file.
 E:mcavc++Debugex1.lib
 Paste the above link to Object/Library
 Build and test the application.

13. DATABASE MANAGEMENT WITH
ODBC

14. Introduction
 Database is used to store data abd provide
access to manipulate the data.
 Use of standard file format.
 Provides multiple user interaction.

15. VC++ Support for Database
Access
 ODBC- set of DLLs, Based on SQL,
independent of any DB protocol.
 DAO- Based on COM interfaces.
 OLE DB- based on COM interfaces.

16. Advantages of Database
Management
 Use of standard file format.
 Indexed file access.
 Data integrity.
 Multi- user access control.

17. ODBC ARCHITECTURE
 Use the ODBC API to access data from a
variety of different data sources.
 Contains Driver manger for performing the
database activities.
 It supports various database drivers
 Microsoft SQL server.
 Oracle.
 Microsoft Access.
 Microsoft FoxPro.
 Implemented by C native API.

18. MFC CLASSES FOR ODBC
 There are 3 different Built in classes provided
by MFC
 CDatabase
 CRecordSet
 CRecordView

19. CRecordSet Functions
 There are several functions are available. They
are,
 CRecordSet::GetSQL()
 GetTableName()
 GetODBCFieldCount()
 Close()
 Open()
 Navigating the data in recordset
 MoveNext()
 MovePrev()
 MoveLast()
 MoveFirst()
 CanScroll()

20.  To Manipulating the data’s in record set
 Delete()
 AddNew()
 CanAppend()
 Edit()
 Update()

21. Recordset Selection
 Visual C++ provides 3 types of Recordser.
They are differ in speed versus features,
 Snapshot Record set.
 Dynaset Record set.
 Table Record set.

22. One Simple Example program
 Create a database and give the ODBC
connectivity.
 Database: student
 DNS source name: student
 Start VC++
 Create a new application by selecting file-
>new.
 Project type: MFC AppWizard(exe).
 Project name: recvew
 Press ok button

23.  In AppWizard,
 Choose single Document
 Select the option “Database view without File
support” And click on the Database source
button-> select the table create previously in the
database and set the Dynaset property.
 Select the CrecordView as the view Class’s Base
Class.
 Select finish button.
 Now a dialog will apper.

24.  Place two edit and two static control.
 View-> class wizard -> member variables tab-
> select the variables as following.
 IDC_EDIT1 m_pSet->m_rollno
 IDC_EDIT2 m_pSet->m_name.
 Resource view-> Add four more manus to the
record menu as follows
 Add record, Delete Record, Update Record, Clear

25.  View-> class wizard-> message maps tab->
 ID_RECORD_ADDRECORD
OnRecordAddrecord()
 ID_RECORD_DELETEREORD
OnRecordDeleterecord()
 ID_RECORD_UPDATERECORD
OnRecordUpdaterecord()
 ID_REORD_CLEAR
OnRecordClear()

26. Type the coding as follows.
 Void CRecvewView::OnRecordAddrecord()
 {
 m_pSet->AddNew();
 UpdateData(true);
 m_pSet->Update();
 UpdateData(false);
 }
 Void CRecvewView::OnRecordUpdaterecord()
 {
 m_pSet->Edit();
 UpdateData(true);
 m_pSet->Update();
 }

27.  Void CRecvewView::OnRecordDeleterecord()
 {
 try
 {
 m_pSet->Delete();
 }
 catch(CDBException *e)
 {
 AfxMessageBox(e->m_strError);
 e->Delete();
 m_pSet->MoveFirst();
 UpdateData(false);
 return;
 }
 UpdateData(false);
 }

28.  Void CRecvewView::OnRecordClear()
 {
 m_pSet->SetFieldNull(NULL);
 UpdateData(false);
 }
Build the program and Run.