On the basis of size of computer

On the basis of size of computer, it can be classified as given below;

• Micro Computer

The Micro computer is the smallest computer system. The size of computer ranges from the size of calculator to the size of desktop computer. But it can perform the same operation and used the same type of instruction as any other computer even then it is small than the others. IT is commonly used in offices, homes, schools etc. Micro computer are also referred to as personal computer, Desktop computer, Home computer or Laptops etc. for example; IBM PC, IBM AT(Advanced Technology).

• Mini Computer

The Mini computer is medium in size i.e. it is also general purposed computer but unlike Micro computer. It serves the multiple uses i.e. many user can work at the same time with the single mini computers to performs data processing, programming, designing and other jobs. Mini computers are used in Government Offices, University, Banks, Industries, Hotels etc. for example; P 3000.

• Mainframe Computer

Mainframe Computer are larger than Mini computer but it is smaller than Super computer. In the comparing with the Mini computer, Mainframe computer have faster processing speed and greater storage capacity and Mini computers are also multi-user system therefore more than 100 users can work at the same time with one Mainframe computer. That's why, they are used in the hotels, industries, banks, airlines, etc. for example; IBM 240.

• Super Computer

Super Computer are the largest, fastest and most expensive special purpose computer in the world. They are designed to process scientific jobs like either for costing scientific research or other especial purposes, for example; CRAY

CPU of computer

CPU(Central Processing Unit)
The full-form of CPU is the shorter form of word Central Processing Unit. The main part of human is brain so the CPU is the brain of Computer. Mostly CPU is called as Processor only but some times it is referred to simply as the central processor. And it is where most calculations take place. In the term of computing power, the CPU is the most important element of a computer system.
The first CPUs were used in the early 1960s. They were custom designed as part of a larger computer, making them prohibitively expensive. The CPUs requires one or more than one printed circuit boards. The CPU is housed in a single chip which is called a Microprocessor.Since the 1970's the class of the microprocessor of CPUs has completely overtaken all other the CPU implementation.
The CPU is itself a internal components of the computer. The modern CPUs are small than old ones and also has square in shape, it contains multiple metallic connectors or pins on the underside. And the CPU is inserted into the CPU socket and its pins are side down on the motherboard. Each motherboard will support only a specific type or range of the CPU so a person mustly check the motherboard manufacturer's specifications before attempting to replace or upgrade a CPU. In the modern CPU, it also have an attached the heat sink and small fan which the air directly goes to the top of computer and helps to prevent from the excessive heat which can damage the computer.
There are 2 typical components of the CPU which are given below;

• The arithmetic logic unit (ALU), which performs arithmetic and logical information.
• The control unit (CU), which extracts instructions from memory, decodes and executes them, calling on the ALU when necessary.
  

computer and it's function

The word COMPUTER has been derived from Latin word 'COMPUTARE' which means to calculate.i.e We can define computer as an electronic machine which performs logical and mathematical performance or performance at a high speed.The modern computer can be defined as an electronic machine design to accept data and instruction,store data and instruction and process data according to the given instruction to produce desire output or result.
So in another word,An Electronic device which can perform in TPO cycle is known as Computer. The full form of IPO is Input Processor Output.
It is the modern type of machine which helps all person either old people or children. It is very useful machine in our daily life. Nowadays people are using computer for the payment of school fees, communication charges, water charges, etc. It helps to make our life easier and happier than others. It brings much of fun to the children because they can play many more interesting games which they like. Younger person can chat with there friends through Facebook.
Function of Computer

• Accept user's supplied data information
• Stere them and perform mathematical operation
  
• Out put the result's according to the user specification
• It can perform mathematical operation
• Transfer the data, image and sound through cable, Telephone line or wireless with very few second. So, it's totally user's dependent drive number. It's own brain so it can't think it's own.
  

Advantages & Disadvantages of Computer

Advantages of Computer
Some of the advantages of using the Computer are as follows:

1. Computer perform functions/calculation at very high speed.
2. Computer can store large volume of data in a small chip or device.
3. It produces 100 percent(%) accurate output.
4. It can be used for different purposes and in different fields like education, medical, banking, entertainment, science and technology.
5. Computer never get tried or bored of doing repetitive type of work unlike human beings.

Disadvantages of computer
Some of the disadvantages of using the Computer are as follows:

1. Computer is an expensive device. It is not within the reach of people.
2. It needs to be instructed as computer can't function it's own.
3. It is an electronic machine, there is possibility of getting shocked.
4. Computer makes human beings lazy and dependency on machine increases.
5. There is chance of data hacking/data leakage therefore security problem.
   

Logic Gates and types of logic gate of computer

Logic Gate :
Logic Gate is an electronic circuit which receive one or more than one input and deliver single output. Different electronic components like transistor, resistor similarly capacitor, diode etc. are used for designing the logic gate. In this logic gate, there are only two state which are one is ON State(1) and another is OFF State(0). ON State can be say High input and High output and OFF State can be say Low input and Low output.ON State means current is passing through the logic circuit and OFF State means current is not passing through the logic circuit.

Types of Logic Gate

• OR Gate
• AND Gate
• NOT Gate
  
• NOR Gate
• NAND Gate
• X-OR Gate
• X-NOR Gate

Boolean function and Universal Gate

Boolean Function
A Boolean function is an expression formed with binary variables , the two binary operators OR and AND, the unary operator NOT, brackets and equal sign.
Example ; F= A'.B+A.B'
F= AB'C+XY'
Universal Gate
The NAND and NOR Gates are universal gate because they are sufficient to implement any Boolean function and can be combine to form any other gate logic gates like OR and NOR AND gates etc.
NAND Gate as universal gate; NOR Gate as universal gate; which both diagram are given below:

Computer memory

Computer Memory
The Memory stores the data and instruction temporarily or permanently which is known as Computer Memory.
Types of Computer Memory

• Primary Memory

It is also known as Main or Internal Memory. It is temporary or volatile memory as it loses its contents when computer is turned off. It stores small amount of data but faster in speed. It has two parts therefore RAM and ROM.

• Secondary Memory

It is also known as auxiliary or external memory. It stores data permanently. It is also non-volatile memory because it does not lose its contents when Computer is turned off. It has large amount of data storage capacity but low in speed. It has two parts therefore Optical and Magnetic.

Number system and its types

Number system
It is an organized and systematic way of representing number.
Types of Number System
1. Binary system
It is a number system with base digits 0 or 1.It can be written as subscripted B or 2.For example:(1001)B or (1001)2
2. Octal number system
It is a number system with base 8 and uses digits 0 to 7.It can be written as subscripted 0 or 8.For example:(205)0 or (205)8.
3. Decimal number system
It is number system with base 10 and use digits 0 to 9.It can be written as subscripted D or 10.For example:(158)10 or (268)D.
4. Idexa Decimal Number system
It is a number system with base 16 and use digits 0 to 9 and symbols A to F.It can be written as subscripted 16 or H.For example:(2AB)H or (ABC)16.

Operating system and its function

Operating System
Operating System is a system software (a set of routine program) that controls and the computer system.It is most important program that run on the computer system and acts as an interface between user and a computer or hardware.

Function Of Operating system
• It controls input and output devices that is used of keyboard,monitor and printer.
• It controls the movements of data in the primary memory.
• It locates and loads program from the secondary memory.
• It saves the programme in the secondary memory.
• It manages the larger programme in the small primary memory of the computer by using the technique of the virtual memory.