A reflex test of the knee is the basis for the term knee-jerk reaction.. A knee-jerk reaction is typically impulsive in nature and doesn't allow for someone to think things through. An outburst of anger is an example of a knee-jerk reaction.
As Figure 1 shows, the central processing unit consists of two parts: The control unit and the arithmetic/logic unit. Each part has a specific function. Before we discuss the control unit and the arithmetic/logic unit in detail, we need to consider data storage and its relationship to the central processing unit.
CPU. In a PC, the central processing unit (CPU) is the primary control device for the entire computer system. The CPU is technically a set of components that manages all the activities and does much of the heavy lifting in a computer system. The CPU interfaces, or is connected, to all of the components such as memory, storage, and input/output (I/O) though communications channels called busses.