Application event in lightning component

Application event are the event handle by any component no matter what relationship between them but they should be inside single application.

Application Event: (Name=AppEvent)

<aura:event type="Application" description="Event template" >

    <aura:attribute name="storeMessage" type="String"/>


</aura:event>

Child Component: (Name=ChildComp) 

<aura:component >
    <aura:registerEvent name="regInChild" type="c:AppEvent"/>
    <aura:attribute name="textMessage" type="String" default="Part from child comp"/>
    <lightning:button label="Click To Fire" onclick="{!c.doHandleEvent}"/>

</aura:component>

Javascript controller:

({
doHandleEvent : function(component, event, helper) {
        var aeEvent=$A.get("e.c:AppEvent");
        aeEvent.setParams({
            storeMessage : component.get("v.textMessage")
            
        });
        aeEvent.fire();
}

})

Parent Component: (Name=ParentComp)

<aura:component >
    <aura:handler  event="c:AppEvent" action="{!c.doHandleFromChild}"/>
    <aura:attribute name="parentMessage" type="String" />
    {!v.parentMessage}

</aura:component>

Javascript controller:

({
doHandleFromChild : function(component, event, helper) {
        var valueFromEvent=event.getParam("storeMessage");
        component.set("v.parentMessage",valueFromEvent);

}

})

Application:

<aura:application extends="force:slds" >
    <c:ParentComp/>
    <c:ChildComp/>

</aura:application>