Now a days computers are coming with multiple processors that enable multiple threads to be executed simultaneously to give performance of applications and we can expect significantly more CPUs in near future. If application is doing CPU intensive tasks and we find that one CPU is taking 100 %usage and others are idle. It might be situation when one thread is doing cpu intensive work and other threads are doing non cpu intensive work. In this case application is not utilizing all CPUs potential here. To get benefits all CPUs Microsoft launches Parallel Programming Library in DotNet Framework 4.0.