How to check whether Oracle instance is started using pfile or spfile?

SQL> show parameter spfile;

NAME       TYPE    VALUE                                                                                                
-------------------------------------------------- ----------- ---------------------------------------------------------------------------------------------------- 
spfile    string   F:\APP\PRABHAKAR\PRODUCT\11.2.0\DBHOME_1\DATABASE\SPFILEORCL.ORA                                     
 

It gives path of spfile file which is getting used by database for starting up. 

It means my database is using spfile 

No value is displayed because database is not using spfile it is using pfile. 

It means database is using pfile for startup.