9. CLASSIFICATION OF COMPUTERS

Computer can be classified into various categories such as:

A. Classification According to Technological Development: 

      First, Second, Third, Fourth and Fifth Generations of Computer.

B. Classification According Purpose:  

     Special Purpose & General Purpose Computers.

C. Classification According to Size:  

     Mainframe, Mini, Micro, Laptop, Notebook and Handheld.

D. Classification According to Function: 

     Digital, Analog & Hybrid Computers.

E. Classification According to Processor: 

    AT, XT, 8086, 8088, 80286, 80486 etc.

A. CLASSIFICATION ACCORDING TO TECHNOLOGICAL DEV.

This examines changes in the various components used in manufacturing computer four decades and beyond. They are:

1. First Generation Computers (1940-1956): They are distinguished by the use of vacuum tubes and Electronic Circuitry Thermionic Valves as the main switching element. The UNIVAC (Universal Automatic Computer) and the  ENIAC (Electronic Numerical Integrator and Calculator) are examples of the 1st generation computers..

Some of the characteristics of first Generation computers are:

1.They are very large in size

i.They produce a lot of heat

ii.They had large memory capacity

iii.They support many terminals/screens

iv.Very Costly

v.Rely on Machine Language to perform operation.

 

 

2. Second Generation Computers (1956-1963): Transistors replaced vacuum tubes ushered in the second generation. Transistor is a device composed of semi conductor material that amplifies a signal or opens or closes a circuit.

i.Generates a lot of heat that subject computers to damage.

ii. Still relied on Punch cards for input

iii. Moved from cryptic binary machine language to Assembly language.

iv. High-level programming languages were also developed ie COBOL, BASIC.

v.The first computers that stored their instructions in their memory, which moved from a magnetic drum to magnetic ore technology.

 

 

3. Third Generation Computers (1964-1971): The development of Integrated Circuit (IC) was the hallmark of the third generation computers. Transistors were miniaturized and placed on silicon chips called Semiconductors, which drastically increased the speed and efficiency of computers.

Some of the characteristics of 3rd  generation computers are:

i. Generates less heat

ii. Uses keyboard and Monitors instead of punch cards and printouts for input.

iii. Interfaced with an  Operating System.

iv. Much Smaller in Size.

v. Cheaper than their predecessors

 

 

4. Fourth Generation Computers (1971-Present): The Microprocessor brought about the fourth generation of computers, as thousands of integrated circuits were built onto a single silicon chip. Microprocessors also control the logic of almost all digital devices, from clock, radios to fuel-injection systems to automobiles.

Three basic characteristics differentiate Microprocessors:

• Instruction Set: The set of instructions that microprocessor can execute.

• Bandwidth: The number of bits processed in a single instruction.

• Clock Speed: Given in Mega hertz (MHz), the clock speed determines how many instructions per second the microprocessor can execute.

5. Fifth Generation Computers (Present and Beyond): Fifth generation computing devices based on Artificial Intelligence are still in development, though there are some applications such as voice recognition that are being used today.

• Games Playing: programming computers to play games such as Chess & Checkers.

• Expert Systems: programming computers to make decisions in real-life situation (for example, some expert systems help doctors diagnose diseases based on symptoms).

• Natural Language: programming computers to understand natural human language.

•Neural Networks: Systems that simulate intelligence by attempting to reproduce the types of Physical connections that occur in animal brains.

•Robotics: programming computers to see and hear and react to other sensory stimuli.

B. CLASSIFICATION ACCORDING TO PURPOSE: This examines various scope where computer is applied which can be specific or general in solving problem, they include:

1. Special Purpose or Dedicated Computers: These are computers that are designed and used for one operation only. Such computers are designed and used only for the operation they were originally intended for and no more. Examples include calculators, Money Counting Machine, Billing Equipment like Meters, Word Processing Equipment, Traffic Light Operations, Industrial Robots and Control Machines, War Guidance Missiles, Games Score Board etc

 2. General Purpose Computers: These computers are designed for many areas of operation. Such computers have multipurpose usage and application. Examples include computers that are used for business data processing and information management.

 

C. CLASSIFICATION ACCORDING TO SIZE: This examines various sizes of computers as are manufactured since the time of invention.

1.Mainframe: In terms of size, the mainframe computers are the largest set of computers as they are manufactured in the early days of invention ie First Generation.
They were bulky in size, produced a lot of heat because of the components used in manufacturing them.

2.Mini Computers: These are next in size to the mainframe. Most mainframe facilities are also found on mini computers. Mini computers are also considered to be scaled down mainframe computers in terms of size.

3. Micro: These are next in size to Mini Computers. They are made up of Large Scale Integration. They are also called Desk top Computers or Personal Computers (PC) are powerful in  terms of information processing.

4. Laptop Computers: As the name implies, the user can keep the computer on the lap and operate it. It perform the same operation as the micro computers depending on the configuration and speed.

4. Hand Held Computers: As the name implies, the computer is held on the palm and operate.

  

D. CLASSIFICATION ACCORDING TO FUNCTION: This examines the nature of work the computer is designed to do using numerical, alphabetical or alphanumeric data in operation.

1. Digital Computers: These computers use discrete signals to represent both numerical and textual data inside memory. The representation is based on binary digits of 0(s) and 1(s) otherwise called Off and On state.

2. Analog Computers: These computers measures changes in continuous physical or electronic state e.g. pressure, temperature, speed, voltage etc. They are essentially measuring devices or instruments examples of Analog computers are Thermometer, Car Speedometer, Barometer, Ammeter etc.

3. Hybrid Computers: These are computers which are conceived as combination of characteristics qualities of both Digital & Analog computers. E.g. of Hybrid computers are: Computers used for application in Control & Feedback Processes, The Computers used by NESA Space shuttles, The computers used for Military Defense etc.

 

E. CLASSIFICATION ACCORDING TO PROCESSOR: By processor we have the following types of computers namely:

1. AT     

2. XT     

3. 8086        

4. 8088   

5. 80286 or 286   

6. Pentium

7. Celeron etc.

The AT, XT, 8086, 8088, 80286 and 80386 brand of computers have date code that ends at 31st Dec. 1999 as they cannot recognize the 2 digit number associated with the new millennium (i.e. 2000) and are liable for millennium bug.

The 80586 and Pentium Pros are popularly called Pentium Processors. These processors have date code that extends beyond year 2000 hence are millennium compliance. Pentium is a registered trademarks of Intel corporation.