Functional Components of Computer

 Functional Components of Computer

Since a computer follows input-process-output cycle, the first stage is performed in computer by input unit, second stage is performed by its central processing unit and the third stage is performed by output unit. Thus the basic structure of a computer is:-

The main memory holds the input and intermidiate output during the processing.

What is Input Unit?

The input unit is formed by the input devices attached to the computer. Examples of input devices and medium are: Keyboard, mouse, magnetic ink character reader (MICR),

optical mark reader(OMR), optical character reader (OCR), joystick etc.

The input unit is responsible for taking input and converting it into computer understandable form (the binary code). Since a computer operates on electricity, it can understand only the language of electricity i.e. either ON or OFF or high voltage or low voltage. That means a computer can understand two stages ON/OFF or High/Low voltage or the binary language that uses just two symbols: 1 for ON and 0 for OFF.

On the same lines, the computer input also consists of data & instructions. For example, if the given input to the computer is Add 2 and 3 then data consists of? and 3 and instruction is Add. Similarly, if the given input is Print Manisha' then data consists of 'Manisha' and instruction is Print.

Input to computers is very crucial as its correctness and aptness is crucial for correct output. There is a term related to it: GIGO - Garbage In Garbage Out, which signifies that garbage input will lead to garbage output only.

WHAT IS CPU?

The CPU is the control centre for a computer. It guides, directs and governs its performance. It is the brain of the computer. The CPU has two components which are responsible for different functions. These two components are its Control Unit (CU) and Arithmetic Logic Unit (ALU).

Arithmetic Logic Unit (ALU)

The ALU performs all the four arithmetical (+, -,,/) and some logical (<, >,=, <=,=, <>) operations. When two numbers are required to be added, these numbers are sent from memory to ALU where addition takes place and the result is put back in the memory. In the same way, other arithmetic operations are performed (through ALU only)

For logical operations also, the numbers to be compared are sent from memory to ALU where the comparison takes place and the result is returned to the memory. The result of a logical operation is either TRUE or FALSE. These operations provide the capability of decision-making to the computer.

Control Unit (CU)

The CU controls and guides the interpretation, flow and manipulation of all data and information. The CU sends control signals until the required operations are done properly by ALU and memory. Another important function of CU is the program execution i.e., carrying out all the instructions stored in the program. The CU gets program instructions from memory and executes them one after the other. After getting the instructions from memory in CU, the instruction is decoded and interpreted i.e., which operation is to be performed. Then the asked operation is carried out. After the work of this instruction is completed, control unit sends signal to memory to send the next instruction in sequence to CU.

The control unit even controls the flow of data from input devices to memory and from memory to output devices.

WHAT IS OUPUT UNIT?

The output unit is formed by the output devices attached to the computer. The output coming from the CPU is in the form of electronic binary signals which needs conversion in some form which can be easily understood by human beings i.e. characters, graphical or audio visual. This function of conversion is performed by output units. Some popular output devices are: monitors VDU (Visual Display Unit), printer, plotter, speakers, speech synthesizer and coder etc.

The Memory 

Well, if a computer has a brain (CPU), it must also have the faculty which we call memory. Indeed, it does possess a memory, however, the memory of a computer is most unlike human memory. A human being can remember stored information for a long time whereas a computer cannot. Its memory is temporary (volatile), it cannot remember anything after it is switched off.

The memory of a computer is more like a predefined working place, where it temporarily keeps information and data to facilitate its performance. When the task is performed, it clears its memory and memory space is then available for the next task to be performed. When the power is switched off, everything stored in the memory gets erased and cannot be recalled.

The memory of a computer can be thought of as 'cells'. Each of these cells is further broken down into smaller parts known as bits (see Fig. 1.3). A bit means a binary digit i.e., either 0 or 1. A number of bits together are used to store data instructions by their combination.

A bit is an elementary unit of the memory. Eight bits together form a byte.