pointer

1

Pointer

• A pointer is a variable that stores an address of another variable of a particular type.

• A pointer has a variable name just like any other variable and also has a type which designates what kind of variables its contents refer to.type* nametype *name

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Example 26#include <iostream.h>int main(){

long *pointer=NULL;long x=10, y=20;pointer=&x;*pointer +=5;cout <<"x = " <<x<<"\t &x= " <<hex <<pointer;cout <<endl;pointer = &y;x=*pointer*10;cout <<endl<<"x= "<<dec <<x<<"\t pointer = " <<hex <<pointer<<"\t *pointer = " <<dec <<*pointer;cout <<endl;return 0;

}

3

Pointer

• Pointer is a variable that holds a memory address.

• Address of a variable is available by using the address - of operator (&).

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Example 27

#include <iostream.h>int main(){

unsigned short x=8;unsigned long y=56432;signed long z=-76543;cout <<"x:\t" <<x <<"\t Address of x: \t" <<&x <<"\n";cout <<"y:\t" <<y <<"\t Address of y: \t" <<&y <<"\n";cout <<"z:\t" <<z <<"\t Address of z: \t" <<&z <<"\n";return 0;

}

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Example 28


unsigned short int x=8;int y=16;unsigned short int *pointerx=0;pointerx=&x;cout <<"x=" <<x <<"\t pointerx=" <<pointerx;cout <<endl;int *pointery=&y;cout <<"y=" <<y <<"\t pointery=" <<pointery;cout <<endl;return 0;

}

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Indirection Operator

• The indirection operator (*) is called the dereference operator.

• The indirection operator mean “the value stored at”.

• When a pointer is dereferenced, the value at the address stored by pointer is retrieved.

7

Example 29


unsigned short int x=8;int y=16, z;unsigned short int *pointerx=0;pointerx=&x;cout <<"x = " <<x <<"\t pointerx = " <<pointerx;cout <<endl;int *pointery=&y;cout <<"y = " <<y <<"\t pointery = " <<pointery;cout <<endl;z=*pointerx + *pointery;cout <<"z = x + y = " <<z ;cout <<endl <<endl;return 0;

}

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Debugging

• When you have written a program that doesn’t work as it should, the debug facilities enable you to work through a program one step at a time to find out where and how it’s going wrong.

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To Display Debug Toolbar

• Select Tools from main menu.• Select Customize from Tool menu.• Select Toolbars tab.• Check the box against Build.• Uncheck Build MiniBar if it is checked.

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Setting Breakpoint

• Place the cursor in the statement where you want execution to stop and click the Insert/Remove Breakpoint button or press F9.

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Removing Breakpoint

• Place the cursor in the same line as an existing breakpoint and click the Insert/Remove Breakpoint button or press F9.

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Starting Debugging

• Select Build from main menu.• Select Start Debug from Build menu.• Select one of the four way listed in Start

Debug submenu.

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GO

• The Go option executes a program to the first breakpoint, where execution will halt.

• After you have examined all you need to at a breakpoint, selecting Go again will continue execution up to the next breakpoint.

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Run to Cursor

• It executes the program up to the statement where you left the cursor in the text editor window.

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Attach to Process

• Enables you to debug a program that is already running.

• This option will list the processes that are running on system.

• You can select the process you want to debug.

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Step Into

• Execute your program one statement at a time.

• It would also execute all the code for stream output (#include).

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Step Over

• Execute the statements in function main( ) and jump over all the code used by the stream operations without stopping.

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Variable Window

• Variable window has three tabs– Auto– Locals– this

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Auto, Local and this Tabs

• Auto tab shows the variables in use in the current and previous statements.

• Local tab shows the values of the variable local to the current function.

• this tab is useful as we progress into object-oriented programming.

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Viewing Variable in the Edit Window

• Position the cursor over the variable for a second.– A tooltip will pop up showing the current value

of the variable.• You can highlight a section and rest the

cursor over the highlighted area and the tooltip will display the value.

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Watching Variables’ Values

• Position the cursor in the Text Editor window in the middle of the variable name.

• Select QuickWatch from the Debug menu.– If you had any problem the whole name or

expression and then select QuickWatch.

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Watching Variables’ Values

• Variable or expressions can be added to Watch window in two other ways:– type the name of the variable into the Name

field in the Watch window– highlight and drag a variable from the Text

Editor or Variables window

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Window Programming

• Microsoft Foundation Classes (MFC).• Single Document Interface (SDI).• Multiple Document Interface (MDI).• AppWizard.

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Window Programming With C++

• AppWizard– for creating the basic program code.

• ClassWizard– for extending and customizing the classes in

programs.• Resource Editor

– for editing or creating such things as menus and toolbars.

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Classes

• A class is a collection of variables often of different types combined with a set of related function.

• A class enables you to bundle various parts and various functions into a single collection called object.

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Classes

• A class can consist of any combination of the variable types and other class types.

• The variables in the class are called the member variable or data member.

• Function in the class typically manipulate the member variables -- that is, what the objects of a class can do.

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Declaring a Class

• Use the class keyword followed by { and then list the data members and function members of that class.class car{int door ;int seats ;speed ( );};

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Access Control in a Class

• Public– means members of an object of the class can be

accessed anywhere within the scope of the class object.

• Private– can only be accessed by member functions of a

class.

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Access Control in a Class

• If you omit the access specification altogether, the members have the default attribute, private.

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Example 30

#include <iostream.h>class box{public:

int length, height, width;};int main(void){

box box1, box2;int volume1=0, volume2=0;box1.length=10, box1.height=12, box1.width=8;box2.length=14, box2.height=13, box2.width=9;

volume1=box1.height*box1.length*box1.width;cout <<endl <<"Volume of Box # 1 is = " <<volume1 <<endl;

volume2=box2.height*box2.length*box2.width;cout <<endl <<"Volume of Box # 2 is = " <<volume2 <<endl <<endl;

return 0;}

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Example 31#include <iostream.h>class box{public:

int length, height, width;int volume(void){ return length*height*width;}

};int main(void){

box box1, box2;int volume1=0, volume2=0;box1.length=10, box1.height=12, box1.width=8;box2.length=14, box2.height=13, box2.width=9;volume1=box1.volume(), volume2=box2.volume();cout <<endl <<"Volume of Box # 1 is = " <<volume1 <<endl;cout <<endl <<"Volume of Box # 2 is = " <<volume2 <<endl <<endl;return 0;

}

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int length, height, width;int volume(void);

};int box::volume(void){

return length*height*width;}int main(void){

box box1, box2;int volume1=0, volume2=0;box1.length=10, box1.height=12, box1.width=8;box2.length=14, box2.height=13, box2.width=9;

volume1=box1.volume(), volume2=box2.volume();cout <<endl <<"Volume of Box # 1 is = " <<volume1 <<endl;cout <<endl <<"Volume of Box # 2 is = " <<volume2 <<endl <<endl;

return 0;}

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int length, height, width;int volume(void);

};inline int box::volume(void){

return length*height*width;}int main(void){

box box1, box2;int volume1=0, volume2=0;box1.length=10, box1.height=12, box1.width=8;box2.length=14, box2.height=13, box2.width=9;volume1=box1.volume(), volume2=box2.volume();cout <<endl <<"Volume of Box # 1 is = " <<volume1 <<endl;cout <<endl <<"Volume of Box # 2 is = " <<volume2 <<endl <<endl;return 0;

}

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int length, height, width;box(int l, int h, int w){

length=l, height=h, width=w;}int volume(void)

{return length*height*width;

}};int main(void){

box box1(10, 12, 8), box2(14, 13, 9);cout <<endl <<"Volume of Box # 1 is = " <<box1.volume() <<endl;cout <<endl <<"Volume of Box # 2 is = " <<box2.volume() <<endl <<endl;

return 0;}

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int length, height, width;box(int l=0, int h=0, int w=0){



}};int main(void){

box box1(10, 12, 8), box2(14, 13, 9);cout <<endl <<"Volume of Box # 1 is = " <<box1.volume() <<endl;cout <<endl <<"Volume of Box # 2 is = " <<box2.volume() <<endl <<endl;

return 0;}

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Example 36


box(int l=0, int h=0, int w=0){



}private:

int length, height, width;};

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Example 36 (continue)

int main(void){

box box1(10, 12, 8), box2(6,8,9);//box2.width=12;cout <<endl <<"Volume of Box # 1 is = " <<box1.volume() <<endl;cout <<endl <<"Volume of Box # 2 is = " <<box2.volume() <<endl <<endl;

return 0;}

If we uncomment the box2.width=12 what will happen? Why?

38

friend Functions

• friend functions are selected functions which are not member of a class to, nonetheless, be able access all members of a class.

• friend functions are not members of the class, and therefore the access attributes do not apply to them.

• friend are just ordinary global functions with special privileges.

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Example 37


box(int l=1, int h=1, int w=1){length=l, height=h, width=w;}int volume(void)


}private:

int length, height, width;friend int boxsurfacearea(box area);

};

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int boxsurfacearea(box area) {

return 2*(area.length*area.width+area.length*area.height+area.height*area.width); }int main(void){

box box1(10, 12, 8), box2(6,8,9);cout <<endl <<"Volume of Box # 1 is = " <<box1.volume() <<endl;cout <<endl <<"Surface area of Box # 1 is = " <<boxsurfacearea(box1) <<endl;cout <<endl <<"Volume of Box # 2 is = " <<box2.volume() <<endl;cout <<endl <<"Surface area of Box # 2 is = " <<boxsurfacearea(box2) <<endl <<endl;return 0;

}

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Example 38


box(int l=1, int h=1, int w=1){length=l, height=h, width=w;}int volume(void)


}int compare(box xbox){return this-> volume()>xbox.volume();}

private:int length, height, width;

};

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int main(void){

int x=0, y=0, z=0;cout <<"length of box # 2 is = ";cin >>x;cout <<endl <<"height of box # 2 is = ";cin >>y;cout <<endl <<"width of box # 2 is = ";cin >>z;box box1(10, 12, 8), box2(x,y,z);if(box2.compare(box1))cout <<endl<<"Box # 1 is smaller than Box # 2";elsecout <<endl<<"Box # 1 is equal to or larger than Box # 2";cout <<endl <<endl;return 0;

}

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Exercises

• Write the code that declares a class called employee with these data members:– age– sex– years of service– salary

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Exercises

• Write a program with the employee class that creates ten employees; sets their age, sex, years of service, and salary; and prints their values.

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Essential Pieces of a Window Program

• WinMain ( )– which is called by windows at the start of

execution of the program.• WndProc ( ) or WindowProc ( )

– which will be called by the operating system whenever a message is to be passed to your application’s window. (procedure for each window class you’ve defined)

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WinMain ( )

• The function WinMain ( ) does any initialization and sets up the window or windows that will be the primary interface to the user.

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WindowProc ( )

• The function WindowProc ( ) handles all the messages that aren’t queued, which will include those initiated in the message loop in WinMain ( ).

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WindowProc ( )

• WindowProc ( ) is where you code your application-specific response to each window message which should handle all the communications with the user by processing the windows message generated by user action.

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MFC

• MFC are a set of predefined classes upon which windows programming with Visual C++ is built.

• MFC represent an object - oriented approach to windows programming that encapsulates the windows API.

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MFC

• All the classes in MFC have names beginning with with C.– Cview– Cdocument

• Data member of an MFC class are prefixed with m_ .– m_lpCmdLine

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MFC

• MFC uses other prefix such as p for pointer, n for an int, l for long, h for a handle.– m_lpCmdLinedata member of class that is of type ‘long pointer’

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Other MFC Prefix

• b a logical variable of type BOOL• by type unsigned char; a byte• c type char• dw type DWORD• fn a function• i int• s string• w WORD

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Create MFC Application

• Step one– Select File from main menu.– Select New from File menu.– Select Win32 Application (under Project Tab).– Type project name. – Click the ok button.

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• Step two– Select Project from main menu.– Select Settings from Project menu.– Select General tab from Project Settings dialog.– Select MFC option (MFC in a Shared DLL).

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• Step three– Create a new source file.– Type your program.– Save.– Build.– Execute.

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To begin programming

• Include the header file afxwin.h– This contains the definitions for many MFC

classes.• To produce the complete program, we’ll

only need to drive two classes from MFC:– application class– window class

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To begin programming

• We won’t need to write a WinMain ( ) function because this is automatically provided by the MFC library.

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The Application Class

• CWinApp is fundamental to any Windows program written using MFC.

• An object of this class includes everything necessary for starting, initializing, running and closing the application.

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The Application Class

• m_nCmdShow– specifies how the application window is to be

shown when the application starts up.• m_pszAppName

– stores a pointer to a string that defines the name of the application.

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The Application Class (example)

class ourApp: public CWinApp{

public:virtual BOOL InitInstance ( );

};

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The Window Class

• FMC application needs a window as the interface to the user, referred to as a frame window. CFrameWnd is designed for this purpose.

• CFrameWnd provides everything for creating and managing a window for an application, all we need to add to our derived window class is a constructor.

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The Window Class (example)

class ourWnd: public CFrameWnd{

public:ourWnd ( ){Create (0, “My first window”);

}};

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Example 39# include<afxwin.h>class OurApp:public CWinApp{public:

virtual BOOL InitInstance();};class OurWnd:public CFrameWnd{public:

OurWnd(){Create(0, "My first window");}

};BOOL OurApp::InitInstance(void){

m_pMainWnd = new OurWnd;m_pMainWnd -> ShowWindow(m_nCmdShow);return TRUE;

}OurApp AnApplication;

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Create an SDI Application With AppWizard

• Select File from main menu.• Select New from File menu.• Select MFC AppWizard(exe) (under project

tab).• Type project name.• Click on ok button.

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• Select the SDI option.• Select the language you like your resources

in.• Click on Next> button.• Click on Next> button once again.

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• This step gives you a range of choices relating to Object Linking and Embedding (OLE), under the label of compound document support.

• OLE enables you to write programs that can import objects from other programs.

• OLE enables you to import your program into another application.

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• The default setting at for this step is ActiveX Controls.– This means that AppWizard will include code

that allows the possibility of using ActiveX controls in our application.

• Accept the default set choice.• Move to next step.

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• This step offers you a range of functions that can be included in your application by AppWizard.– Docking toolbar– Initial status bar– Printing and print preview– Context-sensitive Help– 3D control

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• Docking toolbar– provides a standard range of buttons that are

alternatives to using menu option.• Initial status bar

– status bar appears at the bottom of the application window. (Num Lock, Caps Lock, Scroll Lock)

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• Printing and print preview– This add the standard Page Setup, Print Preview

and Print option to the File menu.• Context-sensitive Help

– Enables a basic set of facilities to support context-sensitive help.

• 3D control– Gives a 3D appearance.

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• The second group of choice concern Window Open Services Architecture (WOSA).

• This is for implementing communication with other computer. This provide two options for communication:– MAPI– Windows Sockets

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• MAPI– This option allows you to send and receive

messages.• Windows Sockets

– This allows you to implement TCP/IP capability within your program.

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• Accepts all the default at this point.• Select the Advanced button.

– This brings up a range of options for your application grouped under two tabs.

• Document Template Strings• Window Styles

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• Document Template Strings– allows to choose the file extension which will

identify files that are generated by your application.

– Allows you to modify the File Type ID• File Type ID is used to label the file type in the

system registry.– Doc type name: entry is a default name for a

document.

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• Type file extension.• Click on Window Styles tab.

– Main frame styles area enable you to tailor your application window.

– Select Thick frame, Minimize box, Maximize box, and System menu.

• Click on Close button to exit from Advanced option.

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• Click on Next > .• This step offers two options

– whether or not comments are to be included in the source code generated by AppWizard.

– Relates how MFC library code is used in your program.

• Default setting is shared DLL (Dynamic Link Library) means that your program will link to MFC library routines at run time.

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• Accept the default setting.• Click on Next >.

– This presents you with a list of the classes that AppWizard will be generating in your program code.

• Click on Finish.• Click on ok

pointer

Documents

int main

viewing variable

unsigned short int x

main menu

zunsigned short int

variable windowvariable

unsigned short x

function main