C Programming : Make it simple

• Data Type
  what an element contains
  what operations you can perform on it.
   
• How can I get what my main function has returned?
  Yes, we can get value return by main.
  suppose, we have written C program is called foo.c and returns int value. 
  $./foo
  $rc=$? #
  $echo rc
  
  here, $? is the return code of the last run program beware of using it in a pipeline. It will get the return value of only last run program.