QA: 
   This is nothing but prevention. It is done by  developer.
QC:
   This is nothing but detection . It is  done by testers.

QA: system mgmt activity involing
planning,assessment,reporting make sure that end of the
product quality needs to meet the customer.
QC:overall the system operational techniques full fill
requirement of the quality.

QC : focus finding and removing defects.

QA: it is purely "process oriented"
QC: It is purely "product oriented"

For further queries contact me

Thanks
Akshay

mail id : akshay_bali2001@yahoo.co.in

Quality Assurance should be done when software development
is under process 
where as Quality control should be done after receiving the
software build from the developers 

QA is done by developers
QC is done by testers

QA is like prevention when s/w is in process
where as QC is detecting and making the defects to be fixed.