Normally, the height of a control is expressed in control units. Each control defines its own meaning for these units. Typically, a control that is n units high will be exactly big enough to hold n lines of text. This allows you to specify the size of a control in logical terms without having to know its exact physical representation on the screen. The HEIGHT-IN-CELLS style overrides this behavior. Instead of using control units, you specify the height of the control exactly, using the cell size of the owning window as the base unit. Thus, a height of one (1) would cause the control to be exactly one row tall.
This option is especially useful in sizing frame control objects. The style allows you to specify the frame's exact dimensions without having to know anything about the frame's title font. You can also specify this style with the CELLS option of the LINES phrase. For example:
LINES = 15 CELLS.
This style is not intended for use in combination with a control's default height. Default heights are based on control units, and when based on character cells, do not typically produce useful results.