QA is preventive activity. its process oriented

QC is detective activity. its main job is to find the 
defects and to fix it.

Quality Assurance is a control of processes;
Quality Control is a control of products.

QA- 
>defect prevention, 
>concentrate on process, 
>involve in entire SDLC, 
>its a staff function 
>quality planning tools and techniqe and quality audit 
methods used.
>Verification
>responsible entire team
>It is planned and systematic set of activities necessary 
to provide adequate confidance that products and services 
will confirm to specified requirments and meet user needs.
QC- 
>Defect detection, 
>concentrate on product
>involve in testing
>its line function
>insepction control charts on basis of work results and 
quality managemnt plan method used
>validation
>responsible tester
>the process by which product quality is compared with 
applicable standards and the action taken when non 
confirmancies is detected.