To implement scrolling in an edit control, you can use the automatic scrolling styles discussed in Edit Control Types and Styles, or you can explicitly add scroll bars to the edit control. To add a horizontal scroll bar, use the style WS_HSCROLL; to add a vertical scroll bar, use the style WS_VSCROLL. An edit control with scroll bars processes its own scroll bar messages. For detailed information about adding scroll bars to edit controls, see Scroll Bars.
The system provides three messages that an application can send to an edit control with scroll bars. The EM_LINESCROLL message can scroll a multiline edit control both vertically and horizontally. The lParam parameter specifies the number of lines to scroll vertically starting from the current line and the wParam parameter specifies the number of characters to scroll horizontally, starting from the current character. The edit control doesn't acknowledge horizontal scrolling messages if it has the ES_CENTER or ES_RIGHT style. The EM_LINESCROLL message applies to multiline edit controls only.
The EM_SCROLL message scrolls a multiline edit control vertically, which is the same effect as sending a WM_VSCROLL message. The wParam parameter specifies the scrolling action. The EM_SCROLL message applies to multiline edit controls only.
The EM_SCROLLCARET message scrolls the caret into view in an edit control. This was done in 16-bit Windows by specifying wParam = FALSE in an EM_SETSEL message. A Win32-based application should use the EM_SCROLLCARET message for the task.