The combo box, list box, and edit controls are encapsulated in the MFC classes CComboBox, CListBox and CEdit, respectively. The Create() function is used to dynamically create and attach each control to a window.

These controls send control notification messages to their parents. The edit control notification messages are prototyped by EN_XXXX, and their message map entry has the form: ON_EN_XXXX(<control ID>,<handler function>). The combo box notification messages are noted by CBN_XXXX, and their message map entry has the form: ON_CBN_XXXX(<control ID>,<handler function>). Similarly, the list box control notification messages are noted by LBN_XXXX, and their message map entry has the form: ON_LBN_XXXX(<control ID>,<handler function>).

The DDX (Do Data Exchange) mechanism “captures” the user input from the controls. It stores the user input from the controls in a member variable attached to each control.