How to enable archive log mode

How to enable archive log mode 
In 10g Automatic archival is default.
But to set up the database is archival mode includes the following steps.

Shutdown the database

SQL > shutdown immediate;

Startup the database in mount mode

SQL > startup mount;

Change DB log mode

SQL > alter database archivelog;

Open the database

SQL > alter database open;

We can check the Db archivelog mode with the following query

SQL > select log_mode from v$database;
   (or)
SQL > archive log list;