en:docs:win16:api:user:messagebox

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en:docs:win16:api:user:messagebox [2026/02/18 02:02] – created prokusheven:docs:win16:api:user:messagebox [2026/03/16 04:56] (current) – prokushev
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 {{page>en:templates:win16api}} {{page>en:templates:win16api}}
  
-======  ======+====== MessageBox ======
  
 ===== Brief ===== ===== Brief =====
 +
 +The **MessageBox** function creates, displays, and operates a message box. The message box contains an application-defined message and title, plus any combination of predefined icons and push buttons.
  
 ===== Syntax ===== ===== Syntax =====
 +<code c>int MessageBox(HWND hWnd, LPCSTR lpText, LPCSTR lpCaption, UINT uType);</code>
  
 ===== Parameters ===== ===== Parameters =====
 +
 +  * hWnd - Handle to the owner window of the message box to be created. If this parameter is **NULL**, the message box has no owner window.
 +  * lpText - Pointer to a null-terminated string containing the message to be displayed.
 +  * lpCaption - Pointer to a null-terminated string used for the dialog box title. If this parameter is **NULL**, the default title "Error" is used.
 +  * uType -  Contains a set of bit flags that determine the content and behavior of the dialog box. This parameter can be a combination of flags from the following groups:
 +
 +**Buttons:**
 +  * **MB_ABORTRETRYIGNORE** - Contains Abort, Retry, and Ignore buttons.
 +  * **MB_OK** - Contains one push button: OK (default).
 +  * **MB_OKCANCEL** - Contains OK and Cancel buttons.
 +  * **MB_RETRYCANCEL** - Contains Retry and Cancel buttons.
 +  * **MB_YESNO** - Contains Yes and No buttons.
 +  * **MB_YESNOCANCEL** - Contains Yes, No, and Cancel buttons.
 +
 +**Icons:**
 +  * **MB_ICONEXCLAMATION / MB_ICONWARNING** - Exclamation-point icon.
 +  * **MB_ICONINFORMATION / MB_ICONASTERISK** - Information icon (i in a circle).
 +  * **MB_ICONQUESTION** - Question-mark icon.
 +  * **MB_ICONSTOP / MB_ICONERROR / MB_ICONHAND** - Stop-sign icon.
 +
 +**Default Button:**
 +  * **MB_DEFBUTTON1** - First button is default (default).
 +  * **MB_DEFBUTTON2** - Second button is default.
 +  * **MB_DEFBUTTON3** - Third button is default.
 +
 +**Modality:**
 +  * **MB_APPLMODAL** - Application-modal (default). User must respond to the message box before continuing work in the current window.
 +  * **MB_SYSTEMMODAL** - System-modal (topmost). All applications are suspended until user responds.
 +  * **MB_TASKMODAL** - Task-modal. Similar to MB_APPLMODAL but used when the calling application has no window handle.
 +
 +**Other:**
 +  * **MB_SETFOREGROUND** - Message box becomes the foreground window.
 +  * **MB_TOPMOST** - Message box is placed above all non-topmost windows.
  
 ===== Return Code ===== ===== Return Code =====
 +The function returns zero if there is not enough memory to create the message box. If the call succeeds, the return value is one of the following menu-item values:
 +
 +  * **IDABORT** - Abort button was selected.
 +  * **IDCANCEL** - Cancel button was selected.
 +  * **IDIGNORE** - Ignore button was selected.
 +  * **IDNO** - No button was selected.
 +  * **IDOK** - OK button was selected.
 +  * **IDRETRY** - Retry button was selected.
 +  * **IDYES** - Yes button was selected.
  
 ===== Notes ===== ===== Notes =====
 +  * In Windows 16 (Janus), the system supports only a limited number of message boxes simultaneously.
 +  * When using the **MB_SYSTEMMODAL** flag, the message box appears on top of all windows and is typically used for critical errors requiring immediate user attention.
 +  * If a message box is created without an owner window (hWnd = NULL), it behaves as an independent window.
 +  * The message box is modal and does not return control until the user closes it by pressing a button.
  
 ===== Example Code ===== ===== Example Code =====
  
 ==== C Binding ==== ==== C Binding ====
 +<code c>
 +#include <windows.h>
 +
 +int PASCAL WinMain(HANDLE hInstance, HANDLE hPrevInstance,
 +                   LPSTR lpCmdLine, int nCmdShow)
 +{
 +    // Simple information message box
 +    MessageBox(NULL,
 +               "Hello, world! This is a message from Janus.",
 +               "Win16 Example",
 +               MB_OK | MB_ICONINFORMATION);
 +
 +    // Question message box with Yes/No/Cancel
 +    int result = MessageBox(NULL,
 +                            "Do you want to save changes?",
 +                            "Confirmation",
 +                            MB_YESNOCANCEL | MB_ICONQUESTION | MB_DEFBUTTON1);
 +
 +    // Handle the result
 +    if (result == IDYES)
 +    {
 +        MessageBox(NULL, "You chose Yes", "Result", MB_OK | MB_ICONINFORMATION);
 +    }
 +    else if (result == IDNO)
 +    {
 +        MessageBox(NULL, "You chose No", "Result", MB_OK | MB_ICONINFORMATION);
 +    }
 +    else if (result == IDCANCEL)
 +    {
 +        MessageBox(NULL, "You chose Cancel", "Result", MB_OK | MB_ICONWARNING);
 +    }
 +
 +    // Error message example
 +    MessageBox(GetActiveWindow(),
 +               "File not found. Please check the path.",
 +               "Error",
 +               MB_OK | MB_ICONSTOP | MB_SYSTEMMODAL);
 +
 +    return 0;
 +}
 +</code>
  
 ==== MASM Binding ==== ==== MASM Binding ====
 +<code asm>
 +; Example for MASM (Microsoft Macro Assembler)
 +; Assemble with: MASM /MX program.asm
 +; Link with: LINK program.obj,,,libw.lib,,
 +
 +.MODEL LARGE
 +.386
 +
 +INCLUDE windows.inc
 +
 +.DATA
 +    msg_hello    DB "Hello, world!", 0
 +    cap_hello    DB "Greeting", 0
 +    
 +    msg_question DB "Continue operation?", 0
 +    cap_question DB "Question", 0
 +    
 +    msg_yes      DB "You pressed Yes", 0
 +    msg_no       DB "You pressed No", 0
 +    msg_cancel   DB "Operation cancelled", 0
 +    cap_result   DB "Result", 0
 +
 +.CODE
 +START PROC FAR
 +    ; Initialize
 +    push    ds
 +    pop     ax
 +    xor     ax, ax
 +    
 +    ; Simple message box
 +    push    MB_OK OR MB_ICONINFORMATION    ; uType
 +    push    OFFSET cap_hello                 ; lpCaption
 +    push    OFFSET msg_hello                  ; lpText
 +    push    0                                  ; hWnd = NULL
 +    call    MessageBox
 +    
 +    ; Question message box
 +    push    MB_YESNOCANCEL OR MB_ICONQUESTION ; uType
 +    push    OFFSET cap_question                 ; lpCaption
 +    push    OFFSET msg_question                  ; lpText
 +    push    0                                      ; hWnd = NULL
 +    call    MessageBox
 +    
 +    ; Check result (result is in AX)
 +    cmp     ax, IDYES
 +    je      show_yes
 +    cmp     ax, IDNO
 +    je      show_no
 +    cmp     ax, IDCANCEL
 +    je      show_cancel
 +    jmp     exit_program
 +    
 +show_yes:
 +    push    MB_OK OR MB_ICONINFORMATION
 +    push    OFFSET cap_result
 +    push    OFFSET msg_yes
 +    push    0
 +    call    MessageBox
 +    jmp     exit_program
 +    
 +show_no:
 +    push    MB_OK OR MB_ICONINFORMATION
 +    push    OFFSET cap_result
 +    push    OFFSET msg_no
 +    push    0
 +    call    MessageBox
 +    jmp     exit_program
 +    
 +show_cancel:
 +    push    MB_OK OR MB_ICONWARNING
 +    push    OFFSET cap_result
 +    push    OFFSET msg_cancel
 +    push    0
 +    call    MessageBox
 +    
 +exit_program:
 +    ; Exit program
 +    mov     ax, 4C00h
 +    int     21h
 +START ENDP
 +
 +END START
 +</code>
  
 ===== See also ===== ===== See also =====
 +  * [[MessageBoxIndirect]]
 +  * [[MessageBeep]]
 +  * [[DialogBox]]
 +  * [[DialogBoxParam]]
 +  * [[CreateDialog]]
 +  * [[FlashWindow]]
 +  * [[GetActiveWindow]]
 +  * [[SetActiveWindow]]
 +
  
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