int MessageBox( const char FAR* lpText, const char FAR* lpCaption = NULL, UINT nType = MB_OK );
lpText
Points to a CString or null-terminated string containing the message to be displayed.
lpCaption
Points to a CString or null-terminated string to be used for the message-box caption. If lpCaption is NULL, the default caption “Error” is used.
nType
Specifies the contents of the message box. It can be a combination of the following values:
| Value | Meaning |
| MB_ABORTRETRYIGNORE | Message box contains three push buttons: Abort, Retry, and Ignore. |
| MB_APPLMODAL | The user must respond to the message box before continuing work in the CWnd. However, the user can move to the windows of other applications and work in those windows. MB_APPLMODAL is the default if MB_SYSTEMMODAL is not specified. |
| MB_DEFBUTTON1 | First button is the default. Note that the first button is always the default unless MB_DEFBUTTON2 or MB_DEFBUTTON3 is specified. |
| MB_DEFBUTTON2 | Second button is the default. |
| MB_DEFBUTTON3 | Third button is the default. |
| MB_ICONEXCLAMATION | An exclamation-point icon appears in the message box. |
| MB_ICONINFORMATION | An icon consisting of a lowercase “i” in a circle appears in the message box. |
| MB_ICONQUESTION | A question-mark icon appears in the message box. |
| MB_ICONSTOP | A stop-sign icon appears in the message box. |
| MB_OK | Message box contains one push button: OK. |
| MB_OKCANCEL | Message box contains two push buttons: OK and Cancel. |
| MB_RETRYCANCEL | Message box contains two push buttons: Retry and Cancel. |
| MB_SYSTEMMODAL | All applications are suspended until the user responds to the message box. Unless the application specifies MB_ICONSTOP, the message box does not become modal until after it is created; consequently, the parent window and other windows continue to receive messages resulting from its activation. System-modal message boxes are used to notify the user of serious, potentially damaging errors that require immediate attention (for example, running out of memory). |
| MB_YESNO | Message box contains two push buttons: Yes and No. |
| MB_YESNOCANCEL | Message box contains three push buttons: Yes, No, and Cancel. |
Creates and displays a window that contains an application-supplied message and caption, plus a combination of the predefined icons and push buttons described in the preceding list.
When a system-modal message box is created to indicate that the system is low on memory, do not take the strings passed as lpText and lpCaption from a resource file, since an attempt to load the resource may fail.
When an application calls the MessageBox member function and specifies the MB_ICONSTOP and MB_SYSTEMMODAL flags for nType, Windows will display the resulting message box regardless of available memory. When these flags are specified, Windows limits the length of the message-box text to one line.
Specifies the outcome of the function. It is 0 if there is not enough memory to create the message box. Otherwise, it is one of the following menu-item values returned by the message box:
| Value | Meaning |
| IDABORT | Abort button pressed |
| IDCANCEL | Cancel button pressed |
| IDIGNORE | Ignore button pressed |
| IDNO | No button pressed |
| IDOK | OK button pressed |
| IDRETRY | Retry button pressed |
| IDYES | Yes button pressed |
If a message box has a Cancel button, the IDCANCEL value will be returned if either the ESC key or the Cancel button is pressed. If the message box has no Cancel button, pressing the ESC key has no effect.
::MessageBox