Lecture 2: Windows Basics

1
Lecture 2 Windows Basics

• Windows is a 32 bit, preemptive, multitasking,
  multithreaded, graphical operating system.
• Preemptive multitasking multiple programs
  executing, OS time slices all programs.
• Multithreaded Program decomposed into multiple
  threads, threads are time sliced.

2
Windows Basics Continued

• Virtualizes video display hardware.
• Application gets handle to a device context.
• Implemented as a set of dynamic link libraries
  (dlls).
• Dlls are not loaded into executable.
• Provide the Application Program Interface (API).
• API dictates event-driven (asynchronous) program
  architecture.
• Reacts to messages sent by OS or application.

3
Unicode

• Characters are 8 bits 256 combinations.
• Unicode extends to 16 bits 65,536 comb.
• Use TEXT(this is a string) macro.
• TCHAR Pointer to a string.
• Static TCHAR grumpy TEXT (I feel grumpy)

4
Printf

• Windows does not understand sdtin, stdout.
• wsprintf(buf, format string, variables)
• char buf100
• int a,b,c, len
• a 10 b 2 c a b
• wsprintf(buf, The sum of a d and b d is
  d, a, b, c)
• s, c, f

5
Program Architecture

• Asynchronous.
• Message driven Logically, program receives
  messages from OS and provides handlers.
• When program begins, OS creates message queue for
  all windows application may create.
• Application provides message loop.
• Polling for messages and causing them to get
  dispatched to the appropriate message processing
  function.

6
Windows Programs

• All windows based on class, each class has
  exactly one message processing function.
• Provide handlers for messages of interest.
• All others handled by default processing
  function.
• Messages are asynchronous (cannot predict which
  msg will be received next).
• Message passing is really the OS calling the
  message processing function for the window.
• Messages can be placed in message queue, or the
  OS can call window procedure directly.

7
Function Prototypes

• include ltwindows.hgt
• LRESULT CALLBACK WndProc (HWND, UINT, WPARAM,
  
  LPARAM)
• Int WinAPI WinMain(HINSTANCE hInstance,
• HINSTANCE hPrevInstance,
• PSTR szCmdLine,
• int iCmdShow)

8
Variable Declarations

• static TCHAR szAppName TEXT(HelloWin)
• HWND hwnd
• MSG msg
• WNDCLASS wndclass

9
Fill in Class Characteristics

• wndclass.style CS_HREDRAW CS_VREDRAW
• wndclass.lpfnWndProc WndProc
• .
• wndclass.hInstance hInstance
• wndclass.hIcon LoadIcon(NULL,
  IDI_APPLICATION)
• wndclass.hCursor LoadCursor(NULL, ID_ARROW)
• wndclass.hbrBackground (HBRUSH)
• GetStockObject(WHITE_BRUSH)
• wndclass.lpszClassName szAppName

10
Register Class

• if (!RegisterClass (wndclass))
• MessageBox (..)
• return 0

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Create Window

• hwnd CreateWindow(szAppName, //set above
• TEXT(The Hello Program), //caption
• WS_OVERLAPPEDWINDOW, //style
• CW_USEDEFAULT, // initial x
  
• CW_USEDEFAULT, // initial y
• CW_USEDEFAULT, // initial x size
• CW_USEDEFAULT, // initial y size
• NULL, //parent window handle
• NULL, // window menu handle
• hInstance, // program instance
  handle
• NULL // creation parameters)

12
Lab 2

• Declare an array of size WM_USER to track
  messages sent but not processes.
• Element 0 of array tracks number of messages of
  type 0 (if message 0 is not processed by
  application), element 1 tracks number of messages
  of type 1and so forth.
• Print out the top 5 such messages.
• Scan the array (at least) 5 times to pick out
  max.
• Have to trap WM_CLOSE message as discussed on Web.