here is the page with the CVS for checking out the latest code base from drupal
Quick notes :
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checkout latest ->
$ cvs -z6 -d:pserver:anonymous:anonymous@cvs.drupal.org:/cvs/drupal checkout drupal
checkout specific version ->
$ cvs -z6 -d:pserver:anonymous:anonymous@cvs.drupal.org:/cvs/drupal co -r DRUPAL-6-12 drupal
update current checkout ->
$ cvs update -dP
