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

This shows database was started by spfile

SQL> show parameter spfile;

NAME    TYPE    VALUE
----    ----   ----------------------------------------------------------
spfile  string /root/apps/oracle/10g/dbs/spfile<DB_NAME>.ora

No values returned means that its started by pfile.

SELECT DECODE(value, NULL, 'PFILE', 'SPFILE') "Init File Type" 
   FROM sys.v_$parameter WHERE name = 'spfile';