UNIT-2 Classification of Computer 2.1        On the basis of working principle – Analog, Digital and Hybrid Computers. 2.2.On the basis of size – Super, Mainframe, Mini and Microcomputers. 2.3.On the basis of brand-IBM PC, IBM Compatible and Apple/Macintosh 2.4.Mobile Computing

Chapter 2 – Classification of Computer

Classification or types of computer

     The grouping or categorization of computer on the bases their different attributes (application, construction, size, work, capacity, speed, Brand, Model and operation) is known as classification of computer.

1.      Classification based on Work (or function or application)

On the basis of the technology that is used for the functioning of the computers, they can be divided in three categories: digital, analog and hybrid.

a)      Analog Computer

@ Analog computers work upon continuous data.

@ Analog computers measure physical magnitudes such as voltage, temperature, current and pressure.

@ It data is represented by physical variable whose magnitude is vary. It is not versatile. It is low accuracy.

@  Examples of analog devices as Speedo meter, thermo meter, Multimeter etc. Some of the popular analog computers are:-

ü  Seismograph used in geography to measure the earthquake.

ü  Speedo meter used in car and motorcycle for calculating their speed.

ü  Mental disease diagnostic device.

ü  In ICU (Intensive Care Unit) of a hospital and heartbeat, blood pressure pulse etc.

b)      Digital Computer

@ Digital computers work upon discontinuous data.

@ These computers work on binary digits 0 and 1.

@ It accuracy is high and fast process.

@ It is versatile.

@ Two types of digital computers:

ü  Special Purpose Computer – Digital Clock, Calculator

ü  General Purpose Computer – PC in computer lab

ü   

Different between analog and digital computer

Analog computer	Digital computer
i. it measures the continuous data.	i. it measures discrete data.
ii. It generate analog signal.	ii. It generate digital signal.
iii. It is slower then digital computer.	iii. It is faster.
iv. It has very low accuracy.	iv. It has very high accuracy.
v. It does single purpose work.	v. It does multi-purpose work.
vi. It has not programming possibility.	vi. It has high programming possibility.
vii. It is not versatile.	vii. It is versatile.
viii. It has less memory capacity.	Viii. It has high memory capacity.
ix. Example of speedometer.	ix. Example of IBM-PC.
x. It is a specific purpose.	x. It is a general purpose.

c)      Hybrid Computer

@ Hybrid computers are computers that comprise features of analog computers and digital computers.

@ The digital component normally serves as the controller and provides logical operations, while the analog component normally serves as a solver of differential equations.

@ It measures both continuous and discrete data.

@ It is commonly used in hospital to measure heart function, temperature, and vital signal of the patient. It is also used industry, scientific research, airplane, and so on. Some of the hybrid computers are FCM (flight management computer, EICAS (Engine indicator crew allot system) and jet plane, Electrocardiogram(ECG), Holter Monitoring machine, Ultra-sound machine, CT-scan machine etc.      

1.      Classification based on Size

      Supercomputer

@ Supercomputer is the most powerful, fastest, largest and expensive in the world.

@ Supercomputer is also known as number crunching.

@ Number of processor is 4 to 16.

@ Clock speed measure greater than 1000 MHZ.

@ It can also process millions of instruction per second..

@ Support multi-user.

@ Used 100 GB RAM and 1000 GB secondary disk.

@ Size is huge.

@ Supercomputer is widely used in government agency and international company.

@ Application: weather maps, construction of atom bombs, Movie animation, Seismography (earthquake prediction), military research, defense system, plasma and nuclear research, in encrypting and decoding sensitive intelligence information etc.

@ It can cost up to thousands of Dollars.

@  Some supercomputers are CRAY-i/ii/iii, CRAY-XMP, SX-2, HITACS-300, CYBER-205, and NEC-500 Etc.

     Mainframe computer

     Mainframe computer is smaller size, capacity and powerful than super computer but, lager capacity, powerful and size and expensive than mini & micro computer. They are used in Hospitals, for companies, banks, airline and railway, communication, reservation systems, census etc. They are also used in LAM, MAN, WAN networking.

@ Mainframe computer is also called Enterprise server.

@ They used number of processor is 1 to 4.

@ Clock speed is greater than 100 MHz.

@ Supports multi-users.

@ It can also process millions of instruction per second.

@ Less expensive than Supercomputer

@ Size is large.

@ Word length is 32 bits or 64 bits.

@ RAM capacity is 8 GB.

@ Mainframe computer can run multiple operating systems hence, they are called virtual machine.

@ IBM 1401 was brought for 2028 B.S census.

@ ICL 2950/10 was brought for 2038 B.S census.

@ Both computers are out-dated so that they kept in the museum of National computer center.

@ It can cost up to thousands of Dollars.

@ Examples are IBM 1404, ICL 2950/10, 1CL 39 series, IBM 4300 series, HP 9000 model 3705/300, HP 9000 model 8705/400 etc.

                                                       

      Minicomputer

           Minicomputer is also known as mid range computer because it has capacity between mainframe and microcomputer.  Minicomputer is smaller size, speed, powerful and storage capacity than supercomputer, mainframe computer and more than microcomputer.  The first minicomputer was launched digital equipment corporation (DEC). Minicomputers are used by government offices,  data processing, programming, desktop publishing fiels,industry, university, organization & other in LAN environment to facilities multiple users.

@ They are used single processor.

@ These computers are preferred mostly by small type of business personals, colleges etc.

@ It’s an intermediary between microcomputer and mainframe.

@ Clock speed is greater than 10 MHz.

@ Supports multi-users.

@ CPU speed is greater than 1 MIPS.

@ Size is medium.

@ Word length is 12 bits.

@ Minicomputer started in the 1958.

@ Examples are HP 3000, PDP-8, PDP-11, HP 9000, NECK, and PLESLE, VAX etc.                                                        

    Microcomputer/Personal Computer

          Microcomputer is the smallest, less powerful, chipset all of them. It is also known as home or personal computer. It is commonly found in home, office, schools, desktop etc. Microcomputer can communicate with LAN, MAN, &WAN with the help of communication device and modem or NIC card. Examples are IBM PC, IBM XT, IBM AT, IMB ps/2 etc.

             A microcomputer contains a (a central processing unit on microchip),in the form of read-only memory and random access memory ,  and a  housed in a unit that is usually called a motherboard .

v  Desktop computer: - They are used in single location, cheap, and have good storage. Examples include: apple, IBM

v  Laptop computer:/ notebook computer - Laptop computer is also known as notebook computer. They are smaller in size, more expensive and rechargeable. Examples include Apple, Acer, and Hewlett Packard (HP).

v  Notebook computers typically weigh less than 6 pounds and are small enough to fit easily in a briefcase. Principal difference between a notebook computer and a personal computer is the display screen. Many notebook display screens are limited to VGA resolution.

v  Hand-held computer PC (PDA): - Also called as palmtop or mobile device. They are smaller in size, have smaller display and input device is generally electronic stylus. Their storage capacity is small. Handheld computer is a pocket-sized computing device, typically having a display screen with touch input or a miniature keyboard. Also called a PDA (Personal Digital Assistant). Some manufacturers are trying to solve the small keyboard problem by replacing the keyboard with an electronic pen. Typically used as an appointment book, address book, calculator, and notepad.  Examples include Apple Newton etc.

v  Pocket computer: - A pocket computer is a small calculator-sized handheld programmable computer. It has only RAM maximum upto 1GB and Hard disk capacity is 80GB.                                            

3. Classification based on Model

  XT (Extended Technology)

@ The computer having 8086(16 bits) or 8088(8 bits) microprocessors are called XT computer.

@ XT computer have processing speed of 4.7 MHz.

@ The XT is old technology where used 4-bits microprocessor.

@ The XT technology only support CUI based operating system.

@ They had less storage capacity.

@ They were very slow.

@ The model refers to first Generation.

  AT (Advanced Technology)

@ This computer had 80286 microprocessor is called AT computer.

@ They are faster and have larger storage capacity than the XT computers.

@ They run latest versions of the software.

@ The higher capacity AT computer may have the micro processors 80386, 486 DX, 486 SX and above Pentium.

@ They used 1.2 MB floppy and 16 bits data bus.

@ They have processing speed more than 100 MHz.

@ AT supports GUI based operating system such as windows.

@ AT technology also supports 64-bits microprocess.

  PS/2 (Personal system/2)

@ IBM Company started manufacturing next model of computer in 1990, which is called PS/2. Most of the computers manufactured after 1990, including laptop computer being to those model.

@ The ps/2 is the new generation of personal computing. 2 stand for second generation.

@ They are faster and high storage capacity disk compare than AT and XT.

@ They can run latest version of computer software.

@ PS/2 technology is refinement version of AT technology.

@ PS/2 technology widely used in laptop as rechargeable devices.

@ In PS/2 technology, at first first runs OS/2 operation system then used windows operating system.

4.  Classification based on Brand

  IBM PC (International Business Machine Personal Computer)

@ The computer manufactured by IBM Company is called IBM computers.

@ It was established in USA in 1924.

@ In 1945, IBM Company started manufacturing mainframe computer, followed by minicomputers and microcomputers.

@ The mainframe, minicomputers and microcomputers manufactured by IBM Company are called IBM Company.

@ These computers are more reliable, durable and have better quality.

@ These computers are manufactured by IBM Company.

@ IBM manufactured mainframe computers followed by mini and microcomputers.

@ The microcomputer manufactured by IBM Company is called as IBM PC.

IBM Compatible

@ It has the same functional characteristics and the principles of IBM PC.

@ Some example of computer ATR, NEC, AST etc.

@ The IBM compatible is not the original IBM computer but their basic architecture is similar to IBM PC

@ All the software or program, which runs in IBM computer, can equally run in IBM compatible.

@ They are less expensive than original computer.

@ They are cheaper and their parts are easily available in the market.

@ Most of the microcomputers used in Nepal are IBM Compatibles.

   Apple /Macintosh                                                           

@ The computer manufacture by Apple Company having different architecture as compared to IBM computer is called Apple computer.

@ The apple company was established in USA in late 1970s.

@ It’s internal architecture totally differ than other own so that it requires own software

@ The apple company has manufacture now brand computer popularly is called Macintosh.

@ It is used for graphics designing.

@ They are quite expensive than IBM and IBM compatible.

@ The O/S and peripherals are completely different the IBM and IBM compatible.

Mobile Computing

Mobile Computing is a technology that allows transmission of data, voice and video via a computer or any other wireless enabled device without having to be connected to a fixed physical link. The main concept involves:

·        Mobile communication

·        Mobile hardware

·        Mobile software

Mobile communication

The mobile communication in this case, refers to the infrastructure put in place to ensure that seamless and reliable communication goes on. These would include devices such as Protocols, Services, Bandwidth, and Portals necessary to facilitate and support of the stated services. The data format is also defined at this stage. This ensures that there is no collision with other existing systems which offer the same service.

Since the media is unguided/unbounded, the overlaying infrastructure is more of radio wave oriented. That is, the signals are carried over the air to intended devices that are capable of receiving and sending similar kinds of signals.

Mobile hardware

Mobile hardware includes mobile devices or device components that receive or access the service of mobility. They would range from Portable laptops, Smartphones, Tablet Pc's, Personal Digital Assistants.

These devices will have receptor medium that are capable of sensing and receiving signals. These devices are configured to operate in full- duplex, whereby they are capable of sending and receiving signals at the same time. They don't have to wait until one device has finished communicating for the other device to initiate communications.

Above mentioned devices use an existing and established network to operate on. In most cases, it would be a wireless network.

Mobile software

Mobile software is the actual program that runs on the mobile hardware. It deals with the characteristics and requirements of mobile applications. This is the engine of that mobile device. In other terms, it is the operating system of that appliance. It's the essential component that makes the mobile device operate.

Since portability is the main factor, this type of computing ensures that users are not tied or pinned to a single physical location, but are able to operate from anywhere. It will incorporate all aspects of wireless communications.

Mobile Computing Classification

Mobile computing is not limited to Mobile Phones only, but also there are various gadgets available in the market helping mobile computing. They are usually classified in the following categories:

Personal Digital Assistant (PDA)

The main purpose of this device was to act as an electronic organizer or day planner that is portable, easy to use and. capable of sharing information with your with a computer systems.

PDA was an extension of the PC, not a replacement. These systems were capable of sharing information with a computer system through a process or service known as synchronization. Where both devices will access each other to check for changes or updates in the individual devices. The use of infrared and Bluetooth connections enabled these devices to always be synchronized.

With PDA devices, a user could; browsers the internet, listen to audio clips, watch video clips, edit and modify office documents, and many more services. They had a stylus and a touch sensitive screen for input and output purposes.

Smartphone

This kind of phone combines the features of a PDA with that of a mobile phone or camera phone. It has a superior edge over other kinds of mobile phones.

Smartphone have the capability to run multiple programs concurrently. These phones include high-resolution touch enabled screens, web browsers that can access and properly display standard web pages rather than just mobile-optimized sites, and high-speed data access via Wi-Fi and high speed cellular broadband.

The most common mobile operating systems (OS) used by modern Smartphones include Google's Android, Apple's iOS, Nokia's Symbian, RIM's BlackBerry OS, Samsung's Bada, Microsoft's Windows Phone, and embedded Linux distributions such as Maemo and MeeGo. Such operating systems can be installed on many different phone models, and typically each device can receive multiple OS software updates over its lifetime.

Tablet PC and I-Pads

This mobile device is larger than a mobile phone or a personal Digital Assistant and integrates into a touch screen and operated using touch sensitive motions on the screen. They are often controlled by a pen or touch of a finger. They are usually in slate form and are light in weight. Examples would include; Ipads, Galaxy Tabs, Blackberry Playbooks etc.

They offer the same functionality as portable computers. They support mobile computing to a far superior way and have enormous processing horse power. User can edit and modify document files, access high speed internet, stream video and audio data, receive and send e-mails, perform lectures and presentations among very many other functions. They have excellent screen resolution and clarity.

Advantages

• Portable: - Mobile computing also reduces transaction cost from one account to another  because of portability and easy communication access
•  Social interactivity: - It iv very useful tool for social interactivity that allows for data sharing and collaboration between users.
•  Content sensitivity: - It is also very useful tool for context sensitivity to gather and respond to real.
• Connectivity ability: - Its connectivity ability helps for communication of data in any environment.
• Quick service: - We can sell a product or give service in quicker time by using mobile computing.
•  Easy and quick enhancement: - Mobile computing is becoming very popular for streamline business processes for its promotion and enhancement easily and quickly.
• Ease of research: -Research has been made easier, since users will go to the field and search for facts and feed them back to the system.
•  Entertainment: -Video and audio recordings can now be streamed on the go using mobile computing. It's easy to access a wide variety of movies, educational and informative material.

Disadvantage

• Insufficient bandwidth: - If the user needs access to a network such as the internet on the go, they must resort to slow wireless WAN’s system primarily intended for telephone use.
• Security Standard: -When working mobile one is dependent on public network, requiring careful use of VPNs(Virtual Private Network).
• Power consumption: - Mobile computers must rely entirely on battery power.\
• Human interface with device: -These are still uncommon, screens are often too small. Keyboards are impractical, especially one-hand, and alternate methods such as speech or handwriting recognition require training.