The Windows Operating System and applications are event-driven. Describe how a Windows application is decoding a WM COMMAND event message to call a Dialog Box from its main message procedure WndProc. You also need to describe the role of the parameters. Refer to the source code example below. Discuss how event-driven systems are beneficial for interactive applications.

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LRESULT CALLBACK WwndProc (HAND hand, UINT message, WPARAM WParam, LPARAM 1Param) int wmId, wmEvent; PAINTSTRUCT ps; HDC hdc; switch (nessage) case WM_COMMAND: wmId - LOWORD (wParam); wmEvent - HIWORD (WParam); I/ Parse the menu selections: switch (wmId) case IDM ABOUT: DialogBox (hinst, MAKEINTRESOURCE(IDD_ABOUTBOX), hind, About); break; case IDM_EXIT: Destroywindow(hiwnd); break; default: return DefwindowProc(hind, message, wParam, 1Param); break; case WM PAINT: hdc - BeginPaint (hwnd, &ps); 1/ TODO: Add any drawing code here... EndPaint (hwnd, Sps): break; case WM_DESTROY: PostQuitMessage(0); break; default: return DefwindowProc (hind, message, wParam, IParam); return e; LRESULT CALLBACK WwndProc (HAND hand, UINT message, WPARAM WParam, LPARAM 1Param) int wmId, wmEvent; PAINTSTRUCT ps; HDC hdc; switch (nessage) case WM_COMMAND: wmId - LOWORD (wParam); wmEvent - HIWORD (WParam); I/ Parse the menu selections: switch (wmId) case IDM ABOUT: DialogBox (hinst, MAKEINTRESOURCE(IDD_ABOUTBOX), hind, About); break; case IDM_EXIT: Destroywindow(hiwnd); break; default: return DefwindowProc(hind, message, wParam, 1Param); break; case WM PAINT: hdc - BeginPaint (hwnd, &ps); 1/ TODO: Add any drawing code here... EndPaint (hwnd, Sps): break; case WM_DESTROY: PostQuitMessage(0); break; default: return DefwindowProc (hind, message, wParam, IParam); return e;

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Windows applications decoding of a WM COMMAND event message is based on UINT WPARAM and LPARAM param... View the full answer