BASIC COMPUTER ORGANIZATION

                       
                                                   BASIC COMPUTER ORGANIZATION

Even though the size, shape, performance, reliability, and cost of computers have been changing over the last

Several years, the basic logical structure (based on the stored program concept), as proposed by Von Neumann, has not changed. No matter what shape and size of computer we are talking about, all computer systems perform the following five basic functions for converting raw input data into useful information and presenting it to a user:

1. Inputting. It is the process of entering data and instructions into a computer system.

2. Storing. It is the process of saving data and instructions to make them readily available for initial or additional processing as and when required.

3. Processing. Performing arithmetic Operations (add, subtract, multiply, divide, etc.), or logical operations (comparisons like equal to, less than, greater than, etc.) on data to convert them into useful information is known as processing.

4. Outputting. It is the process of producing useful information or results for a user, such as printed report or visual display.

5. Controlling. Directing the manner and sequence in which the above operations are performed is known as controlling. The goal of this chapter is to familiarize you with the units of a computer system that perform these functions. It provides an overview of computer systems as computer system architects view them. . Literal architecture of computers differs from one system model to another. However, basic organization remains the same for all computer systems.

Figure 2.1 shows a block diagram of basic computer organization.

In this figure, solid lines indicate flow of instruction and data, and dotted lines represent control exercised by control unit. It displays the live major building blocks(functional units)of a digital computer system. These five units correspond to the live basic operations performed by all computer systems. Functions of each of these units are described below.

 INPUT UNIT:                                                                                        

Data and instructions must enter a computer system before the computer can perform any computation on the supplied data. The input unit that links a computer with its external environment performs this task .Data and instructions enter a computer through an input unit in a form that depends upon the input device used. For example, data can be entered using a keyboard in a manner similar to typing and this differs from the way in which data is entered through a scanner, and other type of input device However, a computer’s memory is designed to  accept input in binary code and hence, all input  devices must transformation input signals to binary codes Units called input interface  accomplish this transformation. Input interfaces match the unique physical or electrical characteristics of Input devices to the requirements of a computer system.

In short, an input unit performs following functions:

1. It accepts (or reads) instructions an data from outside world.

2. It converts these instructions and data in computer acceptable form. Units called input interface: accomplish this task.

3. It supplies the converted instructions and data to the storage unit for storage and further processing.

 OUTPUTUNIT:                                                                                                     

An output unit performs the reverse operation of that of an input unit. It supplies information obtained from data processing to outside world. Hence, it links a computer with its external environment. As computers work with Binary code, results produced are also in binary form. Therefore, before supplying the results to outside world, the system must convert them to human acceptable (readable) form. Units called output interfaces accomplish this Task. Output interfaces match the unique physical or electrical characteristics of output device (terminals, printers.etc) to the requirements of an external environment.

In short on output unit performs following functions:

1. It accepts the produced results. Which are in coded form we cannot understand the coded results easily.

2. It converts these coded results to human acceptable (readable) form. Units called out put Interfaces accomplish this task.

3. It supplies the converted results to outside world.

STORAGE UNIT:                                                                                    

Data and instructions entered into a computer system through input units have to be stored inside the computer before actual processing starts. Similarly, results produced by computer after processing have to be kept some where inside the computer system before being passed on to an output unit. Moreover, a computer must also It Preserve intermediate results for ongoing processing. Storage unit of a computer system caters to all these needs. It

Provides specs for storing data and instructions. Intermediate results and results for output.

In short, a storage unit holds (stores):

1. The dots and instructions required for processing (received from input units).

2. Intermediate results of processing.

3. Final results of processing, before the system releases them to on output unit.

Storage unit of all computers is comprised of following two types of storage:

1. Primary storage: Primary storage of a computer system also known as main memory, Stores pieces of program instructions and data. Intermediate results of processing, end recently produced results of those Jobs(s) on which the computer system is currently working.

The central processing unit can access them Pieces at information directly at a Very fast speed because they are represented electronically in the mail memory chip's circuitry. However, primary storage is volatile, and it loses the information in it as too as the computer systems switches off or resets. Moreover, primary storage normally has limited storey capacity because it is very expensive. Primary storage of modern computer systems is made up of semiconductor devices.

2. Secondary storage: Secondary storage of a computer system, also knows its mortuary storage, takes care of the limitations of primary storage. it supplements the limited storage capacity and volatile characteristic of primary storage. This is because secondary storage is much cheaper than primary storage and it can retain into nation even when the computer system switches off or resets. A computer system uses secondary storage to store program instructions, data, and information of those jobs on which the computer system is currently not working but needs to hold them for processing later. The to commonly used secondary storage medium is magnetic disk.