Module 1: introduction to organization and architecture of computer  (Page 2/4)

• Structure: The way in which the components are interrelated.
• Function: The operation of each individual component as part of the structure.

In term of description, we have to choices: starting ant the bottom and building up to a complete description or with a top view and decomposing the system, describing their structure and function, and proceed to successively lower layer of the hierarchy. The approach taken is this course follows the latter.

Functions

In general terms, there are four main functions of a computer:

• Data processing
• Data storage
• Data movement
• Control

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. However, we shall see that there are only a few fundamental methods or types of data processing.

It is also essential that a computer store data. Event if the computer is processing data on the fly (i.e., data come in and get processed, and the results go right out), the computer must temporarily store at least those pieces of data that are being worked on at any given moment. Thus, there is at least a short-term data storage function. Files of data are stored on the computer for subsequent retrieval and update.

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 id 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 there three functions. Ultimately, this control is exercised by the individual who provides the computer with instructions. Within the computer system, a control unit manages the computer’s resources and orchestrates the performance of its functional parts in response to those instructions.

At this general level of discussion, the number of possible operations that can be performed is few. The [link] depicts the four possible types of operations. The computer can function as a data movement device ( [link] (a)), simply transferring data from one peripheral or communications line to another. It can also function as a data storage device ( [link] (b)), with data transferred from the external environment to computer storage (read) and vice versa (write). The final two diagrams show operations involving data processing, on data either in storage or in route between storage and the external environment.

Structure

[link] is the simplest possible depiction of a computer. The computer is an entity that 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. We will have something to say about both types of linkages.