The position of the scroll box is represented as an integer; it is relative to the left or upper end of the scroll bar, depending on whether the scroll bar is horizontal or vertical. The position must be within the minimum and maximum values of the scrolling range. For example, in a scroll bar with a range of zero through 100, position 50 is in the middle, with the remaining positions distributed equally along the scroll bar. The initial range depends on the scroll bar. Standard scroll bars have an initial range of zero through 100. Scroll bar controls have an empty range — both minimum and maximum values are zero— unless you supply an explicit range when you create the control. You can alter the range at any time after its initial creation. You can use the SetScrollInfo function to set the range values, and the GetScrollInfo function to retrieve the current range values.
You can set a page size for a scroll bar. The page size represents the number of data units that can fit in the client area of the owner window given its current size. For example, if the client area can hold eight lines of text, an application would set the page size to eight. Windows CE uses the page size, along with the scrolling range and length of the scroll bar's gray area, to set the size of the scroll box. Whenever a window containing a scroll bar is resized, an application should call the SetScrollInfo function to set the page size. An application can retrieve the current page size by calling the GetScrollInfo function.