Multitasking? I can’t do two things at once. I can’t even do one thing at a time.

—HELENA BONHAM CARTER

Events do not often occur in a nice, neat, one-at-a-time sequence in real life. Sometimes the wind blows at the same time the rain falls. Other times you might choose to walk and talk simultaneously. Aircraft often bank and accelerate all at once. Not surprisingly, computer programs can also be expected to multitask as well. When software can perform multiple tasks at once, we call it concurrent execution, or just concurrency.