Block diagram of Computer System
👉 A block diagram of computer shows a structural view of a computer system. The block diagram provides you a quick overview of the basic working process of a computer from inputting the data to getting the desired result as output.
The diagram below shows a block diagram of the computer system:-
Even though the size, shape, performance, reliability, and cost of computers have been changing over the last several years, the basic logical structure as proposed by Von Neumann has not changed.
No matter what shape and size of a 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 or logical operations on data to convert them into useful information known as processing.
4. Outputting: It is the process of producing useful information or results for a user, such as a printed report or visual display.
5. Controlling: Directing the manner and sequence in which the above operations are performed is known as controlling.
block diagram of computer
❃In this figure, solid lines indicate the flow of instruction and data, and dotted lines represent control exercised by the control unit. It displays the five major building blocks of a digital computer system. These five units correspond to the five basic operations performed by all computer systems. The 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, another type of input device.
However, a computer’s memory is designed to accept input in binary code, and hence, all input devices must transform input signals into binary codes.
In short, an input unit performs the following functions:-
(i) It accepts instructions and data from the outside world.
(ii) It converts these instructions and data into a computer-acceptable form.
(iii) It supplies the converted instructions and data to the storage unit for storage and further processing.
block diagram of computer
OUTPUT UNIT
An output unit performs the reverse operation of that input unit. It supplies information obtained from data processing to the outside world. Hence, it links a computer with its external environment.
As computers work with binary code, the results produced are also in binary form. Therefore, before supplying the result to the outside world, the system must convert them to a human-acceptable form.
In short, an output unit performs the following functions:-
(i) It accepts the produced results, which are encoded in form. We cannot understand the coded results easily.
(ii) It converts these coded results to a human-acceptable form.
(iii) It supplies the converted results to the outside world.
block diagram of computer
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 a computer after processing have to be kept somewhere inside the computer system before being passed on to an output unit. Moreover, a computer must also preserve intermediate results for ongoing processing. The storage unit of a computer system caters to all these needs.
In short, a storage unit stores:-
(i) The data and instructions required for processing.
(ii) Intermediate results of processing.
(iii) Final results of processing, before the system releases them to an output unit.
The storage unit of all computers is comprised of the following two types of storage:-
block diagram of the computer
1. Primary Storage
The primary storage of a computer system, also known as main memory, stores piece of program instructions and data, intermediate results of processing, and recently produced results of those jobs on which the computer system is currently working.
The CPU can access these pieces of information directly at a very fast speed because they are represented electronically in the main memory chips circuitry.
However, primary storage is volatile, and it loses the information in it as soon as the computer system switches off or resets. Moreover, primary storage normally has limited storage capacity because it is very expensive. The primary storage of modern computer systems is made up of semiconductor devices.
block diagram of computer
2. Secondary Storage
Secondary storage of a computer system, also known as auxiliary storage, takes care of the limitations of primary storage.
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 most commonly used secondary storage medium is a magnetic disk.
block diagram of computer
ARITHMETIC LOGIC UNIT (ALU)
A computer performs all calculation and comparison operations in the ALU. During the processing of a job, the computer transfers data and instructions stored in its primary storage to ALU as and when needed.
ALU does the processing and the computer temporarily transfers the intermediate results generated there back to primary storage until needed later. Hence, data may move back and forth several times between primary storage and ALU before the processing of the job is over.
The engineering design of a computer ALU determines the type and number of arithmetic and logic operations that a computer can perform.
However, almost all ALUs are designed to perform the four basic arithmetic operations (add, subtract, multiply, and divide) and logic operations or comparisons such as, less than, equal to, and greater than.
block diagram of computer
CONTROL UNIT (CU)
❃ How does an input device of a computer system know that it is time for it to feed data to a storage unit?
All this is possible due to the control unit of the computer system.
A computer’s control unit does not perform any actual processing of jobs but acts as the central nervous system for other components of the computer system.
It manages and coordinates the operations of all other components. It obtains instructions from a program stored in the main memory, interprets the instructions, and issues signals causing other units of the system to execute them.
CENTRAL PROCESSING UNIT (CPU)
CU and ALU of a computer system are together known as the CPU. It is the brain of a computer system. In the human body, the brain takes all major decisions, and other parts of the body function as directed by the brain.
Similarly, in a computer system, the CPU performs all major calculations and comparisons and also activates and controls the operations of other units of the computer system.
block diagram of computer
THE SYSTEM CONCEPT
You might have observed that we have been referring to a computer as a system. This is because a system is a group of integrated parts having a common purpose of achieving some objective. Hence, a system has the following three characteristics:
(i) It has more than one element.
(ii) All its elements are related logically.
(iii) All its elements are controlled in a manner to achieve the system goal.
Since a computer has integrated components that work together to perform the steps called for in an executive program, it is a system. Input and output units cannot function until they receive signals from the CPU. Similarly, the storage unit or CPU alone is of no use.