ReadPrefix is used internally by the component streaming system. It is called automatically by ReadComponent to read flags that determine whether a component in an inherited form (ffInherited), whether its creation order in the form is important (ffChildPos), and whether it is a top-level component such as a form or data module (ffInline). It also reads the component's position in the ancestor form's creation order if the ffChildPos flag is set. When a writer object writes a component to its stream, it prefixes the component with these flags. 

ReadComponent