Computer Notes Chapter -4 The Computer Generations ! First Generation (1942-1955) ! Characteristic ! Advantages ! Disadvantages ! Second Generation (1955-1964) ! What is Transistor ! Characteristic ! Advantage ! Disadvantage ! Third Generation (1964-1975) ! Integrated Circuits (ICs) ! Chip ! Characteristics ! Advantage ! Disadvantages ! Fourth Generation (1975- Onward) ! Characteristics ! Advantage ! Disadvantage ! Fifth Generation (Yet to come) !

The Computer Generations:

    In computer, talk is a step in technology It provides a framework for the growth of the computer industry. Originally, the term 'generation' was used to distinguish between varying hardware technologies. But nowadays, it was been extended to include both the hardware and the software, which together make up an entire computer system. 

First Generation (1942-1955)

  We have already discussed about some of the early computers ENIAC. EDVAC. EDSAC, etc. These machines and other of their time were made possible by the invention of "vacuum tube" which was a fragile glass device that could control and amplify electronic signals. These vacuum tube computers are referred to as first generation computers. 

Characteristics :

 1. The first generation computer control was centralized in a single C.P.U.

 2. Ferrite - core main memory was started as storage. 

 3. Use of virtual memory and register started .

 4. Punch card used as input device.

 5. Magnetic tapes and magnetic drums used as secondary memory 

 6. Binary code or machine language was used for programming.

 7. Advent of von-Neumann Architecture. 

  

Advantages :

   i.  Vacuum tubes were the only electronic components available during those days.

   ii. Vacuum tube technology made possible the advent of electronic digital computers.

   iii. These computers were the fastest calculating devices of their time.

   iv.  They could perform computation in milliseconds. 

Disadvantages :

  i. Tool bulky in size.

  ii. Unreliable.

  iii. Thousand of vacuum that were used emitted large amount of heat and burnt out                     frequent.

  iv.  Air conditioning required.

  v.   Prone to frequent hardware failures.

  vi.  Constant maintenance required.

  vii.  Non-portable.

  viii.  Manual assembly of individual component into functioning unit required.

  xi.    Commercial production was difficult and constly. 

  x.     Limited commercial use.     

Second Generation (1955-1964):

 

The transistor is a smaller and more reliable successor to the vacuum tube. was invented in 1947. However. computers. that used transistors were not produced in quantity  until over a decade later. The second generation emerged with transistors being the brain of the computer.

 

With both the first and second-generation computers, the basic component was a discrete or separate entity. The many thousands of individual components had to be assembled by hand into functioning circuits. The  manual assembly of individual components and the cost of labours at involved at this assembly stage made the commercial production of these computers difficult and costly.

What is Transistor :

    It is made from silicon. It is cheaper and smaller than vacuum tube. Unlike vacuum tubes, a transistor does not require wires, metal glass capsule and vacuum therefore, it is called solid-stage device. The transistor was invented in 1947 and has launched the electronic revolution in 1950.

Characteristic:

 i. Greater speed, large memory capacity and smaller size than previouse generation.

 ii. More advanced in terms of ALU&CU.

 iii. Assembly language was used for programming. 

 iv.  Cost reduced.

 v.   Less power consuming.

 vi.  High- level language were beginning to be used and provisions for system software              were starting. 

 

Advantage :

i.  Smaller in size as compared to first generation computers.

ii. More reliable.

iii. Less heat generated.

iv. These computers were able to reduce computational times from milliseconds to                     microseconds  

v. Less prone to hardware failures.

vi. Better portability.

vii. Wider commercial use.

Disadvantage :

  i. Air-Conditioning required.

  ii. Frequent maintenance required.

  iii. Manual  assembly of individual components into  a functioning unit was required.

  iv. Commercial production was difficult and constly.

 Third Generation (1964-1975):

      Use of ICs in computer defines the third generation of computer. Computers of third generations are faster than previous generations. Due to ICs the size of the computer reduced in this generation. 

Example-IBM system/360 family have model 30,40,50,65

Integrated Circuits (ICs):

   ICs are collection of reansistors, registers and conductors. They are fabricated on a semi- conductor material such as- Silicon. Hundreds or even thousands of transistors could be fabricated on a single water of Silicon. These fabricated transistors can be connected with a process of metallization to from logic circuits on the same chip. The silicon water is divided into a matrix of small areas. Size of area is few millimeters.  Circuit pattern is fabricated on each of these areas and then water is broken into Chip.

Chip :

  Each chip consists of several gates, which are made using transistors only and a number of input & output connection points. Each chip  can be packaged separately in a housing to protect it.

Hundreds or even thousands of transistors could be fabricated on a single wafer of silicon. Wafer divided into 5 mm square areas, where chip fabricated .

Characteristics :

  i. IC was used on the place of transistors.

  ii. High-level language was used for programming.

  iii. Memory size increases.

  iv. Certain new techniques were introduced to increase the effective speed of program               execution.

 v. Sent conductor memories were starting  on the place of ferrite  core memory as main            memory 

Advantage :

i. Smaller in size as compared to previous generation computers.

ii. Even more reliable than second-generation computers. 

iii. Even lower heat generated than second generation computers.

iv. These computers were able to reduce computational time from microseconds to                       nanoseconds 

v. Maintenance cost is low because hardware failure is rare.

vi. Portable.

vii. Totally general purpose. Widely used for various commercial application all over the           world. 

 viii. Manual assembly of individual components into a functioning unit not required .So                  human labour and cost involved at assembly stage reduced drastically .

  xi. Commercial production was easier and cheaper .

Disadvantages :

 i. Air-Conditioning required in many cases.

ii. Highly sophisticated technology required for the manufacture of IC chips.

Fourth Generation (1975-Onward) :

 

 Intially, the integrate  circuits contained only about ten to twenty components.

Characteristics :

  On the basis of number of gates integrated on a single chip ICs be classified into fllowing categories 

1. Small - Scale Integration (SSI)

    Only few gates ( Components) were integrated on a chip and then packaged.

2. Medium - Scale Integration (MSI)

    Hundreds (100) of gates were fabricated on a single chip. 

3. Large - Scale Integration (LSI)

    There are 1000 of gates were fabricated on a single chip.

4. Very- Large Scale Integration (VLSI)

      There are 1000,000 gates are fabricated a single chip. 

5. Ultra- Scale Integration (ULSI)

     There are 1000,000,000 components are expected are expected be fabricated.

    

  Example- Intel 8080

Advantage :

  i. Smallest in size because of high components density 

  ii. Very reliable.

  iii. Heat generation is negligible .

  iv. No air conditioning  required in most cases. 

  v. Much faster in computation than previous generations.

  vi. Hardware failure is negligible and hence minimal maintenance is required .

  vii. Portable because of their small size.

  viii. Totally general purpose.

  xi. Cheapest amoung all generation .

Disadvantage :

 i. Highly sophisticated technology required for the manufacture of LSI  chips.

Fifth Generation (Yet to come) :

  Scientists are now at work on the fifth  generation computers- a promise, but not yet a reality. They aim to bring us machines with genuine I.Q.  the ability to reason logically, and with real knowledge of the world. Thus, unlike the last four generation, which naturally followed its predecessor, the generation will be totally different, totally novel, and totally new.