Backup without using SQL Server Management Studio
You can use sqlcmd from the command prompt.

It's default location for SQL 2012 is here :- C:\Program Files\Microsoft SQL Server\110\Tools\Binn

For windows authentication run :- sqlcmd -SSERVERNAME

or for sql authentication run:- sqlcmd -SSERVERNAME -ULogin -PPassword

You can then run a backup sql statement.

http://msdn.microsoft.com/en-us/library/ms180944.aspx