Should this question be reopened?  
*Noooooooo*

It's not only basic knowledge for most who use MSSQL.  
Which doesn't actually matter all that much.

But primarily!  
It is [a][1] [clear][2] [duplicate][3].  
There are so many posts on serverfault / dba about the memory usage of SQL Server, I don't see why it's not just closed as a duplicate.  
It would answer the OP's question quite quickly if it was just closed as a duplicate, serve as a pointer to the tremendous amount of answers about SQL Server memory, and push the point _please do your own research_ more than simply closing it does. (not taking into account comments who are generally regarded as non-existent in the long run)

When a question comes up that is clearly common knowledge, chances are you'll find a post on ServerFault about it. For any other questions a well written ServerFault answer won't harm anyone if one does not already exist.

  [1]: http://serverfault.com/questions/93789/sql-server-slowly-hogging-ram-where-do-i-start-to-optimise
  [2]: http://serverfault.com/questions/387682/how-do-i-limit-ms-sql-server-memory-usage
  [3]: http://serverfault.com/questions/363134/sql-server-2008-should-i-set-minimum-server-memory