An application sends an EM_SETPASSWORDCHAR message to set or remove the password character for a single-line edit control when the user types text. When a password character is set, that character is displayed in place of each character the user types.
EM_SETPASSWORDCHAR wParam = (WPARAM) (UINT) ch; // character to display lParam = 0; // not used; must be zero
This message does not return a value.
When the EM_SETPASSWORDCHAR message is received by an edit control, the edit control redraws all visible characters by using the character specified by the ch parameter.
If the edit control is created with the ES_PASSWORD style, the default password character is set to an asterisk (*). This style is removed if an EM_SETPASSWORDCHAR message is sent with the ch parameter set to zero.