Introduction
Computer architecture deals with the functional behavior of a computer system as viewed by a programmer. This view includes aspects such as the sizes of data types (e.g. using 16 binary digits to represent an integer), and the types of operations that are supported (like addition, subtraction, and subroutine calls). Computer organization deals with structural relationships that are not visible to the programmer, such as interfaces to peripheral devices, the clock frequency, and the technology used for the memory. This textbook deals with both architecture and organization, with the term “architecture” referring broadly to both architecture and organization.
Charles Babbage
1791-1871
The Grandfather of Computer
Babbage’s machines had a means for reading input data, storing data, performing calculations, producing output data, and automatically controlling the operation of the machine. These are basic functions that are found in nearly every modern computer.
von Neumann Model
Conventional digital computers have a common form that is attributed to von Neumann
The Input Unit provides instructions and data to the system, which are subsequently stored in the Memory Unit. The instructions and data are processed by the Arithmetic and Logic Unit (ALU) under the direction of the Control Unit. The results are sent to the Output Unit. The ALU and control unit are frequently referred to collectively as the central processing unit (CPU). Most commercial computers can be decomposed into these five basic units.
System Bus Model
Most important to the system bus model, the communications among the components are by means of a shared pathway called the system bus, which is made up of the data bus (which carries the information being transmitted), the address bus (which identifies where the information is being sent), and the control bus (which describes aspects of how the information is being sent, and in what manner). There is also a power bus for electrical power to the components, which is not shown, but its presence is understood. Some architectures may also have a separate I/O bus.