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.
All computers contain a central processing unit that interprets and executes instructions; input devices, such as a keyboard and a mouse, through which data and commands enter the computer; memory that enables the computer to store programs and data; and output devices, such as printers and display screens, that show the results after the computer has processed data.