Lecture 08

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					                              Chapter 8


8.1 BRIEF HISTORY OF WIN32                2
8.2 WINDOWS COMPONENTS                    3
8.2.1 KERNEL                              3
8.2.2 GDI (GRAPHICS DEVICE INTERFACE)     3
8.2.2.1 Pens                              4
8.2.2.2 Brushes                           4
8.2.3 USER                                7
8.2.3.1 Clipboard                         7
8.3 HANDLES IN WINDOWS                    7
8.4 OUR FIRST WIN32 PROGRAM               8
SUMMARY                                   9
                                    Windows Basics                                        2




8.1 Brief History of Win32

 Before starting windows programming lets take a short look at the history of Windows.
• In 1983 Windows announced for the first time in history.
• In November 1985 Windows 1.0 is launched.
• In April 1987 Windows 2.0 shipped.
• In 1988 Windows/386 emerged out. This version of Windows supported Multiple
   DOS boxes. DOS boxes are the Consol windows which are enabled to get input or
   show output only in text form or character form and no GUI is supported in this mode.
• November 1989 Win word 1.0 finally shipped.
• In May 1990 Windows 3.0 shipped. It is designed to operate in 3 Modes. These are

    A. Real Mode or 8086 mode
    B. Protected Mode or 286 mode
    C. Enhanced or 386 mode with multiple DOS boxes and with support of Virtual
    Memory. In virtual Memory some of the area on Hard disk is used as system Memory.

•   Late 1991 Windows version 3.1 released. This version of Windows came with the
    Multimedia extensions that later became the part of Windows standard builds.
•   Late 1992 Windows NT beta version released. And with this version Win32 API also
    published. Windows NT offers preemptive Multitasking.
    Multitasking is of two types.

       1. Preemptive Multitasking. In Preemptive multi tasking, the operating system
           parcels out CPU time slices to each program.
       2. Cooperative or Non Preemptive Multitasking. In this type of multitasking
       each program can control the CPU for as long as it needs it. If a program is not
       using the CPU it can allow another program to use it temporarily.

•   Summer 1993, Windows NT version 3.1 is launched. This version of windows is
    enabled to run as well, on MIPS and Alpha CPU’s as Intel x86 CPU.
•   Summer 1994 Windows version 3.5 is launched.
•   In August 1995 Windows95 shipped. Windows95 was designed for home computing.
•   September 1995 Windows version 3.51 released. And it is considered as the most
    solid version of NT for servers.
•   Summer 1996, Support for the MIPS and PowerPC machines are dropped.
•   June 1998, Windows98 released with built in Internet Explorer version 4.
                                    Windows Basics                                      3


•   September 1998, Visual Studio 6.0 released. Visual Studio6.0 consists of three
    languages i.e. Visual C++, Visual Basic and Visual J++. Visual studio comes in three
    categories, i.e. learner or student edition, professional and Enterprise edition.
    Visual C++ is a compiler that will be using in the Windows programming course. This
    Visual C++ compiler would be the part of Professional or Enterprise Visual Studio
    package.

•   Feb 2000 Windows 2000 released with major improvements. It is proved to be a much
    stable version than the earlier versions of Microsoft Windows series of Operating
    systems. It is also called Windows NT5.

8.2 Windows Components
Microsoft Windows consists of three important components. These are:
1. Kernel
2. GDI (Graphics Device Interface)
3. User

8.2.1 Kernel
Kernel is a main module of the operating system. This provides system services for
managing threads, memory, and resources.
Kernel has to perform very important responsibilities e.g.

1. Process Management
2. File Management
3. Memory Management (System and Virtual Memory)

In Windows Operating System Kernel is implemented in the form of Kernel32.dll file.
The Kernel is responsible for scheduling and synchronizing threads, processing,
exception and interrupts. Loading applications and managing memory. Kernel is
responsible for the system stability and efficiency.

8.2.2 GDI (Graphics Device Interface)

GDI is a subsystem responsible for displaying text and images on display devices and
printers. The GDI processes Graphical function calls from a Windows-based application.
It then passes those calls to the appropriate device driver, which generates the output on
the display hardware. By acting as a buffer between applications and output devices, the
GDI presents a device-independent view of the world for the application while interacting
in a device-dependent format with the device.
                                     Windows Basics                                      4


GDI is responsible to display application’s graphics objects on Screen and Printer. The
Applications that use GDI need not worry about Graphics Hardware because GDI
provides the suitable device independent interface. In GDI subsystem, anything we want
to display or print, there’s Device context or DC. Device context or DC is a logical term
in windows. Whenever we have to display something, we get DC of display device, and
whenever we have to print something we get DC of printer device.
GDI is implemented in the form of library GDI32.dll. This library contains all the APIs
that need to draw graphics or text objects. We can write text, and draw rectangles,
polygons, lines, points, etc by using Pens and Brushes:

8.2.2.1 Pens

A pen is a graphics tool that an application for Microsoft Windows uses to draw lines and
curves. Drawing applications use pens to draw freehand lines, straight lines, and curves.
Computer-aided design (CAD) applications use pens to draw visible lines, hidden lines,
section lines, center lines, and so on. Word processing and desktop publishing
applications use pens to draw borders and rules. Spreadsheet applications use pens to
designate trends in graphs and to outline bar graphs and pie charts.

Each pen consists of three attributes: style, width, and color. While no limits are imposed
on the width and color of a pen, the pen's style must be supported by the operating
system. These styles are illustrated in the following figure.


   Solid

   Dash

   Dot

   Dash-Dot

   Dash-Dot-Dot

   Null

Figure 1 Pens types

8.2.2.2 Brushes

A brush is a graphics tool that a Windows based application uses to paint the interior of
polygons, ellipses, and paths. Drawing applications use brushes to paint shapes; word
processing applications use brushes to paint rules; computer-aided design (CAD)
                                     Windows Basics                                      5


applications use brushes to paint the interiors of cross-section views; and spreadsheet
applications use brushes to paint the sections of pie charts and the bars in bar graphs.

There are two types of brushes: logical and physical. A logical brush is one that you
define in code as the ideal combination of colors and/or pattern that an application should
use to paint shapes. A physical brush is one that a device driver creates, which is based
on your logical-brush definition.

Brush Origin

When an application calls a drawing function to paint a shape, Windows positions a
brush at the start of the paint operation and maps a pixel in the brush bitmap to the
window origin of the client area. (The window origin is the upper-left corner of the
window's client area.) The coordinates of the pixel, that Windows maps, are called the
brush origin.

The default brush origin is located in the upper-left corner of the brush bitmap at the
coordinates (0,0). Windows then copies the brush across the client area, forming a pattern
that is as tall as the bitmap. The copy operation continues, row by row, until the entire
client area is filled. However, the brush pattern is visible only within the boundaries of
the specified shape. (Here, the term bitmap is used in its most literal sense—as an
arrangement of bits—and does not refer exclusively to bits stored in an image file).

There are instances when the default brush origin should not be used. For example, it
may be necessary for an application to use the same brush to paint the backgrounds of its
parent and child windows and blend a child window's background with that of the parent
window.

The following illustration shows a five-pointed star filled by using an application-defined
brush. The illustration shows a zoomed image of the brush, as well as the location to
which it was mapped at the beginning of the paint operation.
                                      Windows Basics                                    6




Figure 2 Brush Origin (Description from MSDN)

Logical Brush Types

Logical brushes come in three varieties: solid, pattern, and hatched.

       A solid brush consists of a color or pattern defined by some element of the
       Windows user interface (for example, you can paint a shape with the color and
       pattern conventionally used by Windows to display disabled buttons).
       A hatched brush consists of a combination of a color and of one of the six patterns
       defined by Win32. The following table illustrates the appearance of these
       predefined patterns.

Brush Style                                      Illustration

Backward diagonal

Cross-hatched

Diagonally cross-hatched

Forward diagonal
                                     Windows Basics                                      7


Horizontal

Vertical

Figure 3 Brush Styles

8.2.3 User

User component manages all the user interface elements.
User interface elements include Dialogs, Menus, Text, Cursor, Controls, Clipboard, etc.
User component is implemented in User32.dll file. You would be familiar with all the
user interface elements but the new thing for you might be Clipboard.

8.2.3.1 Clipboard

In Windows, data is shareable among applications. For example you are typing in
Notepad and after you have typed, you want to copy all the text written in Notepad to
another Editor, say, MS Word. How could this be possible? The answer is: through
clipboard. Yes, in clipboard, firstly we copy all the data to clipboard and then paste that
data to MS Word because clipboard is shareable object. All the text or image data you
have previously copied can now be pasted in other application.

Following are some of the features of clipboard.

    •   User32.dll manages clipboard.
    •   Clipboard is used to cut copy and paste operations.
    •   Clipboard is temporary storage area. When you shut down windows, data saved in
        clipboard will be lost.

8.3 Handles in Windows
A term handle is a 32 bit number in Win32 environment. It is normally a type defined as
void *. Handle has an extensive use in Windows. Using handles you can destroy, release
and take other actions on the object. The basic types of handles in windows are:

    •   HANDLE
    •   HWND
    •   HINSTANCE

HWND is of type Handle to Window.
HINSTANCE is of type Handle to instance of the application.
                                     Windows Basics                                      8


Every application has unique identifier in Memory that is called an instance of the
application.

8.4 Our first Win32 Program
For writing win32 program you should be familiar of programming concepts in C++.

First we will include header file windows.h in our source file because this header contains
prototype of useful APIs that will be used in our windows programs. This header also
contains some other headers required for commonly used APIs.

#include <windows.h>

Every Windows GUI base program starts its execution from the WinMain API. And
Every Windows console base program starts its execution from simple main function.
Here we will be discussing about Windows Graphical User Interface programs.
So we will start our program by writing WinMain.

int CALLBACK WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR
lpCmdLine,int nCmdShow)
{
        MessageBox(NULL, “This is the First Windows Program \n Author: Shahid”,
        “Virtual Uinversity”, MB_OK|MB_ICONINFORAMTION);
return 0;
}

WinMain:
WinMain is the starting point in Every Win32 GUI programs. WinMain has four
Parameters these are,
1) First is instance of the current application.
2) Second parameter is also an instance of this application which is used for the previous
application of the same type that is already running. It is used only in Window 16bit
editions or Windows 3.1. Windows 32bit editions do not support this parameter. It is here
just for compatibility.
3) Third parameter is a command line argument of string type which is a type defined as
char *.
4) Fourth parameter is windows style.

Calling Convention:
CALLBACK is a calling convention which is a type defined as __stdcall.
Return Value:
In our application WinMain returns 0. WinMain always returns a value of type integer.
                                    Windows Basics                                      9



MessageBox:
MessageBox API is used to display a message on screen. It comes in windows dialog
form and has caption and client area, both of these contains strings. It also has buttons,
like Ok, Cancel, Yes, No, Retry, Abort. It has four arguments.
1) First is the HANDLE to window, this handle is a parent handle of the messagebox. In
our case it has no parent handle so we write NULL here that shows that it has parent
desktop.
2) Second parameter is a string type which print string in the body of the message box
which is also called client area of the message box
3) Third parameter is also a string type it prints string in a caption of the message box.
4) Fourth parameter is a buttons that will be displayed in the message box. We presented
here some of the constants like MB_OK|MB_ICONINFORMATION which display ok
button and icon information on the left side of the message box. These constants can be
presented here by using bitwise OR operator.


Summary
In this Lecture, we studied about the windows history about when and how different
editions were released. Then we learnt about the windows components: Kernel, GDI and
User. Kernel is the heart of Operating system and GDI is a Graphics device interface in
windows which is used to display and print graphics and text objects. Then we studied
user component which is responsible to control all the dialogs, menu, windows, Windows
controls, etc. ‘Handles in windows’ is the introductory part of handles used in windows.
Handles are 32 bit number that may be void * type which is defined in ‘WinUser.h’
header file. Finally we wrote our first Win32 program. We always write WinMain in
every windows program because WinMain is the starting point of Windows Programs.
And we learnt how to display message box in WinMain function and then we returned
from WinMain with the returned value Zero. And we discussed about the Message box
API and explained its parameters as well.

Tips: Never use second parameter (HINSTANCE) of WinMain because it is not used in
recent version of windows. In future lectures, we will discuss how to determine the
existence of previous application.
                                   Windows Basics                                   10



Copyright

Some of the course material and Documentation on Microsoft Windows APIs has been
taken from Microsoft for the preparation of Win32 course. This course has been designed
and prepared by Virtual University.

Microsoft, Visual C++, Windows, Windows NT, Win32, and Win32s are either
registered trademarks or trademarks of Microsoft Corporation.

				
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