in in drupal , what is ; $Id:
i know for when we use this ; $Id:,strong text for create block , we should first create .info module, this tell to drupal about the our module/ block / menu inform ,
my question what is necessary of ; $Id:
What is the use ,
In which place it is calling ,
$Id$ is the concurrent versions system (CVS) identification tag. If we want to share our module with others by checking it into Drupal’s contributed modules repository, this value will automatically be replaced by CVS.
It's not necessary, but as Loveleen says, if you want to commit your module/theme to Drupal CVS repository and share it with the world, you must put the CVS Id tag in the first line of your php, javascript, css and .info files.
It must be written inside of a comment (the first line of the file), so depending of the file:
For PHP and Javascript files: // $Id$
For CSS files: /* $Id$ */
In the .info file the comment lines start with ; so you must write ; $id$
More info in the Coding Standards and Header comment blocks