Organization and Architecture
What is the computer architecture?
Computer architecture refers to those attributes of a system visible to a programmer or, put another way, those attributes that have a direct impact on the logical execution of a program.
What is the computer organization? Give examples.
Computer organization refers to the operational units and their interconnections that realize the architectural specifications. Examples of architectural attributes include the instruction set, the number of bits used to represent various data types (e.g., numbers, characters), I/O mechanisms, and techniques for addressing memory. Organizational attributes include those hardware details transparent to the programmer, such as control signals; interfaces between the computer and peripherals; and the memory technology used.
Historically, and still today, the distinction between architecture and organization has been an important one. Many computer manufacturers offer a family of computer models, all with the same architecture but with differences in organization. Consequently, the different models in the family have different price and performance characteristics. Furthermore, a particular architecture may span many years and encompass a number of different computer models, its organization changing with changing technology. A prominent example of both these phenomena is the IBM System/370 architecture. This architecture was first introduced in 1970 and included a number of models.
The customer with modest requirements could buy a cheaper, slower model and, if demand increased, later upgrade to a more expensive, faster model without having to abandon software that had already been developed. Over the years, IBM has introduced many new models with improved technology to replace older models, offering the customer greater speed, lower cost, or both. These newer models retained the same architecture so that the customer’s software investment was protected. Remarkably, the System/370 architecture, with a few enhancements, has survived to this day as the architecture of IBM’s mainframe product line.
What is a hierarchical system?
A computer is a complex system; contemporary computers contain millions of elementary electronic components. A hierarchical system is a set of interrelated subsystems, each of the latter, in turn, hierarchical in structure until we reach some lowest level of elementary subsystem. The hierarchical nature of complex systems is essential to both their design and their description. The designer need only deal with a particular level of the system at a time. At each level, the system consists of a set of components and their interrelationships. The behavior at each level depends only on a simplified, abstracted characterization of the system at the next lower level.
What are the structures and the functions?
At each level, the designer is concerned with structure and function:
- Structure: The way in which the components are interrelated
- Function: The operation of each individual component as part of the structure
What are the basic functions of the computer system?
Both the structure and functioning of a computer are, in essence, simple. The basic functions that a computer can perform. In general terms, there are only four:
Describe the basic functions of the computer system.
The computer, of course, must be able to process data. The data may take a wide variety of forms, and the range of processing requirements is broad.
It is also essential that a computer store data. Even if the computer is processing data on the fly (i.e., data come in and get processed, and the results go out immediately), the computer must temporarily store at least those pieces of data that are being worked on at any given moment.
The computer must be able to move data between itself and the outside world. The computer’s operating environment consists of devices that serve as either sources or destinations of data. When data are received from or delivered to a device that is directly connected to the computer, the process is known as input–output (I/O), and the device is referred to as a peripheral. When data are moved over longer distances, to or from a remote device, the process is known as data communications.
Finally, there must be control of these three functions. Within the computer, a control unit manages the computer’s resources and orchestrates the performance of its functional parts in response to those instructions.
What is the structure of the Computer Architecture?
The computer interacts in some fashion with its external environment. In general, all of its linkages to the external environment can be classified as peripheral devices or communication lines. But of greater concern in this book is the internal structure of the computer itself. There are four main structural components:
- Central processing unit (CPU): Controls the operation of the computer and performs its data processing functions; often simply referred to as processor.
- Main memory: Stores data.
- I/O: Moves data between the computer and its external environment.
- System interconnection: Some mechanism that provides for communication among CPU, main memory, and I/O. A common example of system interconnection is by means of a system bus, consisting of a number of conducting wires to which all the other components attach.
What are the main components of Computer Architecture?
However, for our purposes, the most interesting and in some ways the most complex component is the CPU. Its major structural components are as follows:
- Control unit: Controls the operation of the CPU and hence the computer
- Arithmetic and logic unit (ALU): Performs the computer’s data processing functions
- Registers: Provides storage internal to the CPU
- CPU interconnection: Some mechanism that provides for communication among the control unit,ALU, and registers.