<b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; hInst,NULL</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp; mov&nbsp;&nbsp; hwnd,eax</b> <br>
  <b>&nbsp;&nbsp;&nbsp; invoke ShowWindow, hwnd,SW_SHOWNORMAL</b> <br>
  <b>&nbsp;&nbsp;&nbsp; invoke UpdateWindow, hwnd</b> <br>
  <b>&nbsp;&nbsp;&nbsp; .WHILE TRUE</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke GetMessage, ADDR msg,NULL,0,0</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .BREAK .IF (!eax)</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke TranslateMessage, ADDR 
  msg</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke DispatchMessage, ADDR msg</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp; .ENDW</b> <br>
  <b>&nbsp;&nbsp;&nbsp; mov&nbsp;&nbsp;&nbsp;&nbsp; eax,msg.wParam</b> <br>
  <b>&nbsp;&nbsp;&nbsp; ret</b> <br>
  <b>WinMain endp</b> 
<p><b>WndProc proc hWnd:HWND, uMsg:UINT, wParam:WPARAM, lParam:LPARAM</b> <br>
  <b>&nbsp;&nbsp;&nbsp; .IF uMsg==WM_DESTROY</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke PostQuitMessage,NULL</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp; .ELSEIF uMsg==WM_COMMAND</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov eax,wParam</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .if ax==IDM_OPEN</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov ofn.lStructSize,SIZEOF 
  ofn</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; push hWnd</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; pop&nbsp; 
  ofn.hwndOwner</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; push hInstance</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; pop&nbsp; 
  ofn.hInstance</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov&nbsp; 
  ofn.lpstrFilter, OFFSET FilterString</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov&nbsp; 
  ofn.lpstrFile, OFFSET buffer</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov&nbsp; 
  ofn.nMaxFile,MAXSIZE</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov&nbsp; 
  ofn.Flags, OFN_FILEMUSTEXIST or \</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  OFN_PATHMUSTEXIST or OFN_LONGNAMES or\</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  OFN_EXPLORER or OFN_HIDEREADONLY</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov&nbsp; 
  ofn.lpstrTitle, OFFSET OurTitle</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke 
  GetOpenFileName, ADDR ofn</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .if eax==TRUE</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke lstrcat,offset OutputString,OFFSET FullPathName</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke lstrcat,offset OutputString,ofn.lpstrFile</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke lstrcat,offset OutputString,offset CrLf</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke lstrcat,offset OutputString,offset FullName</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  mov&nbsp; eax,ofn.lpstrFile</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  push ebx</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  xor&nbsp; ebx,ebx</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  mov&nbsp; bx,ofn.nFileOffset</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  add&nbsp; eax,ebx</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  pop&nbsp; ebx</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke lstrcat,offset OutputString,eax</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke lstrcat,offset OutputString,offset CrLf</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke lstrcat,offset OutputString,offset ExtensionName</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  mov&nbsp; eax,ofn.lpstrFile</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  push ebx</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  xor ebx,ebx</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  mov&nbsp; bx,ofn.nFileExtension</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  add eax,ebx</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  pop ebx</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke lstrcat,offset OutputString,eax</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke MessageBox,hWnd,OFFSET OutputString,ADDR AppName,MB_OK</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke RtlZeroMemory,offset OutputString,OUTPUTSIZE</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .endif</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .else</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke 
  DestroyWindow, hWnd</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .endif</b> <br>
  <b>&nbsp;&nbsp;&nbsp; .ELSE</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke DefWindowProc,hWnd,uMsg,wParam,lParam</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ret</b> <br>
  <b>&nbsp;&nbsp;&nbsp; .ENDIF</b> <br>
  <b>&nbsp;&nbsp;&nbsp; xor&nbsp;&nbsp;&nbsp; eax,eax</b> <br>
  <b>&nbsp;&nbsp;&nbsp; ret</b> <br>
  <b>WndProc endp</b> <br>
  <b>&nbsp;end start</b> <br>
<hr width="100%">
<h3> Analysis:</h3>
<b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov ofn.lStructSize,SIZEOF 
ofn</b> <br>
<b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; push hWnd</b> 
<br>
<b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; pop&nbsp; 
ofn.hwndOwner</b> <br>
<b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; push hInstance</b> 
<br>
<b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; pop&nbsp; 
ofn.hInstance</b> 
<p>We fill in the routine members of ofn structures. 
<p><b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov&nbsp; 
  ofn.lpstrFilter, OFFSET FilterString</b> 
<p>This FilterString is the filename filter that we specify as follows: 
<blockquote><b>FilterString db "All Files",0,"*.*",0</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  db "Text Files",0,"*.txt",0,0</b></blockquote>
Note that All four strings are zero terminated. The first string is the description 
of the following string. The actual pattern is the even number string, in this 
case, "*.*" and "*.txt". Actually we can specify any pattern we want here. We 
MUST put an extra zero after the last pattern string to denote the end of the 
filter string. Don't forget this else your dialog box will behave strangely. 
<p><b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov&nbsp; 
  ofn.lpstrFile, OFFSET buffer</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov&nbsp; 
  ofn.nMaxFile,MAXSIZE</b> 
<p>We specify where the dialog box will put the filename that the user selects. 
  Note that we must specify its size in nMaxFile member. We can later extract 
  the filename from this buffer. 
<p><b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov&nbsp; 
  ofn.Flags, OFN_FILEMUSTEXIST or \</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  OFN_PATHMUSTEXIST or OFN_LONGNAMES or\</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  OFN_EXPLORER or OFN_HIDEREADONLY</b> 
<p>Flags specifies the characteristics of the dialog box. <br>
  OFN_FILEMUSTEXIST&nbsp; and OFN_PATHMUSTEXIST flags demand that the filename 
  and path that the user types in the filename edit control MUST exist. <br>
  OFN_LONGNAMES flag tells the dialog box to show long filenames. <br>
  OFN_EXPLORER flag specifies that the appearance of the dialog box must be explorer-like. 
  <br>
  OFN_HIDEREADONLY flag hides the read-only checkbox on the dialog box. <br>
  There are many more flags that you can use. Consult your Win32 API reference. 
<p><b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mov&nbsp; 
  ofn.lpstrTitle, OFFSET OurTitle</b> 
<p>Specify the title of the dialog box. 
<p><b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; invoke 
  GetOpenFileName, ADDR ofn</b> 
<p>Call the GetOpenFileName function. Passing the pointer to the ofn structure 
  as its parameter. <br>
  At this time, the open file dialog box is displayed on the screen. The function 
  will not return until the user selects a file to open or presses the cancel 
  button or closes the dialog box. <br>
  It 'll return the value TRUE in eax if the user selects a file to open. It returns 
  FALSE otherwise. 
<p><b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .if eax==TRUE</b> 
  <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke lstrcat,offset OutputString,OFFSET FullPathName</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke lstrcat,offset OutputString,ofn.lpstrFile</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke lstrcat,offset OutputString,offset CrLf</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke lstrcat,offset OutputString,offset FullName</b> 
<p>In case the user selects a file to open, we prepare an output string to be 
  displayed in a message box. We allocate a block of memory in OutputString variable 
  and then we use an API function, lstrcat, to concatenate the strings together. 
  In order to put the strings into several lines, we must separate each line with 
  a carriage return-line feed pair. 
<p><b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  mov&nbsp; eax,ofn.lpstrFile</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  push ebx</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  xor&nbsp; ebx,ebx</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  mov&nbsp; bx,ofn.nFileOffset</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  add&nbsp; eax,ebx</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  pop&nbsp; ebx</b> <br>
  <b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke lstrcat,offset OutputString,eax</b> 
<p>The above lines require some explanation. nFileOffset contains the index into 
  the ofn.lpstrFile. But you cannot add them together directly since nFileOffset 
  is a WORD-sized variable and lpstrFile is a DWORD-sized one. So I have to put 
  the value of nFileOffset into the low word of ebx and add it to the value of 
  lpstrFile. 
<p><b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke MessageBox,hWnd,OFFSET OutputString,ADDR AppName,MB_OK</b> 
<p>We display the string in a message box. 
<p><b>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
  invoke RtlZerolMemory,offset OutputString,OUTPUTSIZE</b> 
<p>We must *clear* the OutputString before we can fill in another string. So we 
  use RtlZeroMemory function to do the job. <br>
  <strong><br>
  </strong>
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