ParentComponent.component

<apex:component controller="ParentComponentController">
  <apex:attribute name="componentValue" description="Attribute on the component."
                  type="String" required="required" assignTo="{!controllerValue}"/>
    <apex:pageBlock title="My Parent Custom Component">
      <p>
        <code>componentValue</code> is "{!componentValue}"
        <br/>
        <code>controllerValue</code> is "{!controllerValue}"
      </p>
    </apex:pageBlock>
    <p>
    	Notice that the controllerValue has been upper cased using an Apex method.
    </p>
    <p>
    	Calling Child Component: 
    </p>  
    <c:ChildComponent componentValue="Hi there, {!$User.FirstName}"/>
</apex:component>