Functional Block Diagram of a Computer System

Input

Data needs to be fed into the computer before the computer can process it and give us the final output. Input devices do just that. They take in the input from the user, transform it into the form which the computer can interpret and then pass that data to the computer for further processing. Examples include Mouse, Keyboard, Webcams, Scanners etc

 Storage Unit

Computers need a temporary as well as a permanent storage facility. Therefore, the two categories of storage devices are primary and secondary.

Primary Storage - The data that is fed in by the input device needs to be stored temporarily before it can be processed. Also the intermediate results of the computations and processing have to be stored somewhere in order to obtain the final output. These kinds of storage are very fast but since they are very costly (and complex to manufacture) only the least amount of such storage is included in computers. They usually store the program that is currently being executed and certain other codes and data that are required for the purpose of processing. Primary memory is volatile in nature; i.e. the data stored in it is erased after the power is cut off from the device.

Secondary Storage - Secondary storage is a high capacity dirt cheap storage solution. It is a more permanent solution of storing data as it is non-volatile. We can access data from this kind of storage at a later point in time.

Output Unit

After the input devices feed in the data and the system processes it, we must find a means by which the output can be readily made available to the end user. Therefore, the devices that make the result of the computation readily available to the end user are known as output devices. Monitors, printers and speakers – just to name a few.

Arithmetic Logical Unit

As its name suggests this unit performs the basic calculations such as addition, subtraction, multiplication and division. It also has the capability to perform logical operations such as >, <, >= etc. The control unit will transfer the data to ALU when there is a need to perform tasks that can be carried out by this unit. After the results have been computed, the ALU sends the data to the storage device which in turn sends it to the output device.

Control Unit

Control unit is considered as the central nervous system of a computer. It guides the input devices to store the data into the right location. It also controls the flow of data between the storage device and the ALU.

Central Processing Unit: The control unit along with the ALU is known as CPU.