Classification Of Computer

                    Classification of the computers based on their data processing abilities .They  are classified according to purpose ,data handling and functioning .

 Classify by Purpose: 

They are two type of computers according to purpose.
General purpose 
 Specific purpose  
General purpose computers are built to perform a range of task and have the ability to store a large amount of data (programmes) .The efficiency of general purpose computers are low.
Specific purpose computers are design to perform a specific task . The  efficiency of   specific purpose computers are  much better than general purpose computers

Classify by Data handling :

There are three types according to data handling.
Analog computers 
Digital computers 
Hybrid computers
Analog computers :The principle of analog computers is measuring . These measuring are translated into data .such computers do not deal with the numbers .They measure continuous physical magnitude .
Digital computers : They operates with numbers or information.The data in digital computers are represented in digital form(0s and 1s).The results of digital computers are more accurate , efficient and faster .
Hybrid computers : They contain the features of  both analog computers and digital computers .Analog computers are use for computational purposes and digital computers are use for storage .

Classify by function :

Servers
Workstations 
Information Appliances
Embedded computers
Servers : Server computers provide a specific service. Such as Database Server is a computer to provide a Database service. Web Servers provide a web page and web applications
Workstations: These computers are intended to serve one user and contain special hardware not found on a personal computer .
Information  Appliances: These computers are design to perform a specific tasks . such as editing text and playing music
 Embedded computers : These computers are intended to operate a specific machine or device . Automobile may contain a number of embedded computers . Washing machine and DVD player contain only one embedded computer.

Classify by Size:-

 There are four categories
Micro computers 
Mini computers 
Main frame computers 
Super computers 
Micro computer system : These are normally standalone computers known as Personal computer (PC) or desktop computers . It is a small computer based on microprocessor .  These are expensive computers and only one user can use at one time . It contain two type of memories RAM  and ROM .
user friendly software are use in micro computer .
Example are :
Desktop computer
 In_car computer
Game consoles
laptops and notebook computer
Smartphone
Programmable calculator
Mini computer system : Special software operate these computer . They can support more than one person usually from 4-200 user simultaneously .Mini computer are expensive and use as departmental computer or governmental institutions for data processing like hospital , universities , business. They are use as a server .
Main frame computer system : It is very large and expensive computers . hundred and thousand user use it simultaneously . It is mainly use in hospitals , universities  and world governing body .
Super computer system : Super computers are fastest and very expensive . These computers require a lot of mathematical calculations .  Modern super computers  system are equipped with many processors enabling them to handle complex operation for example weather forecast . First super computer was developed by VON -Newman .

Generations Of Computer

            The generations of a computer is different from one an other, the difference between generations of computer depends on the technology that are used in computer. Due to these technology computer operate differently. From past to now the device of a computer become a more efficient, reliable, smaller and cheaper.
There are five generations of a computer based on the technology that are used are
First Generation: Vacuum Tubes
Second Generation: Transistors
Third Generation: Integrated Circuit
Fourth Generation: Microprocessors
Fifth Generation: Artificial Intelligence

First Generation:Vacuum Tube:-

                           The first generation of a computer used a Vacuum Tube Technology for magnetic drums for memory. The first generation computer depends on the low level programming language (machine language). The low level programming language is written in binary format (0,1). This language is very difficult to learn and understand. The detail knowledge of hardware is required to write a program. This generation could solve one problem at one time. The input in first generation was based on punch card and output was displayed on printouts. The first generation computers were often enormous and occupy a entire room.
The example of first generations are
Electronic Discrete Variable Automatic (EDVAC)
Electric Numerical Integrator And Computer (ENIAC)
Universal Automatic Computer (UNIVAC)

Second Generation: Transistors:-

                                           Second Generation used Transistor instead of Vacuum Tube. Transistor makes a computer more reliable, efficient, smaller and cheaper and energy efficient as compared to Vacuum Tube, that's why it is superior to Vacuum Tube. Second Generation of computer used a Assembly language. Assembly language is one step higher then low level language. Assembly language use a symbol to specify a instruction to perform a particular task.Like to first generation second generation also used a punch card for input and for output it used printouts.
The examples of this generation are
IBM-1620
IBM-1401
 CDC-3600

Third Generation:Integrated Circuit:-

                           Integrated circuit was the hallmark of Third Generation of a computer. Third generation computer based keyboards and monitors interface of operating system instead of punch card and printouts that allow a device to run different application at a one time with central program. The Third Generation computer used a high level language. High level language is much closer to human language but not directly understood by machine. Translators are required to run program efficiently. All instruction are written in human language so it is easy for human to understand easily, and for first time computer is available for people to used. Third Generation Computer is smaller and cheaper as compared to previous Generations.
The example of
IBM-360
 IBM-370
 ICL-1900
 VAX-750

Fourth Generation:Microprocessor:-

                               Microprocessor brought a revolution in computer history. The thousand of Integrated Circuits were built on single silicon chip. The single silicon chip controls a all components of a computer from central processing unit to memory. The development of GUI, mouse and handheld device are possible by fourth generation. The Fourth Generation Computer are smaller, cheaper, more powerful and efficient.
In 1947 first Intel 4004 chip is develop.
In 1984 Apple introduce the Macintosh.
In  1981 IBM introduce first home used computer for public.

Fifth Generation:Artificial Intelligence:-

                           Fifth Generation computers used an Artificial Intelligence approach. What is Artificial Intelligence???? Artificial Intelligence is an engineering technique to make a machine Intelligent. The machine perform a functions like a human beings.
Voice recognition, ROBOT is an example of Fifth generation.

Types of Computer Memory and their Management

In computing memory refer to a device which is used to store a information for immediate used in a computer.
A computer memory is divided into two broad categories which is known as
primary memory
secondary memory

Primary memory:- 

                            primary memory is a internal memory of a computer. It contained on a computer chips and used a electronic circuits to store information. In primary memory, data is not stored permanently, the data is lost when the computer is turn off. The access speed of a internal memory is very high as compared to secondary memory because it accessed directly by the central processing unit.
There are different type of a primary memory are
Read Only Memory (ROM)
Flash Memory
Random Access Memory (RAM)

Read Only Memory:-

                          In Read Only Memory instructions are stored permanently, the store data is not removed when the computer is turn off. Read Only Memory is a Non-volatile Memory. ROM contain a instructions that is very important for computer to start up (boots up). The instructions are read before software program load in the computer from a small program in the ROM. The small program or small part of a ROM is called a "BIOS". Read Only Memory is not re writable it allow only reading. Read Only Memory contain data when computer is switched off.

Flash Memory:-

                       Flash Memory is a solid, Non-volatile and re writable memory. The Flash Memory is used in digital camera's, cell phones, printers,Audio recorders and hand held computers because the speed of Flash Memory is high and the Flash Memory used a low voltage.

Random Access  Memory:-

                                        Random Access Memory is a storage device that can be accessed randomly at any time in any order and from any location. Random Access Memory is a volatile memory. what is volatile memory????
In volatile memory the stored data is lost when computer is off and data remain in memory when machine or computer is running.
Random Access Memory is a readable and re writable memory. We can read data from memory at any time and we can delete the data at any time and again we write data in the memory.
There are two types of Random Access Memory
Static Random Access Memory
Dynamic Access Memory

Static Random Access Memory:-

                                                   Static RAM is a volatile memory it never needs to be refreshed the stored information as power is applied. The content of memory is lost when power is turn off.

Dynamic Random Access Memory:-

                                                         Dynamic RAM is a volatile memory it needs to refreshed the stored information periodically otherwise stored information would be vanish.

Secondary Memory:-

                                 secondary memory is slower than primary memory. Secondary memory is not directly connected to the computer. It hold data after the computer is turn off. Secondary memory has a large capacity to store information but the Access speed of memory is slow. Secondary memory use a inexpensive mass-storage device so secondary memory is inexpensive.
Types of Secondary Memories are
Magnetic Storage Media
Optical Storage Device
Magnetic Storage Device:-

Management of computer memory:-

               The management of computer memory is very important to operate correctly otherwise it leads to bugs, slow performance and virus in the computer.
Arithmetic overflow, segmentation fault, memory leak are all problem of improper management of memory.
Virtual memory and Protected Memory is used to properly manage the computer memory.

Virtual Memory:-

                          When a program needs a memory it request to operating system then operating system decide the location of physical memory to place the memory.
The benefit of virtual memory is where the memory is stored physically without the worry of computer space.

Protected Memory:-

                              In protected memory particular range of memory is allocated to each program to run properly. When program tried to used the space of other program then system terminate the program and help to save data to used incorrectly. protected memory is used to enhanced the reliability and security of the computer system.
       

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