COMPUTER GENERATIONS

COMPUTER GENERATION :

" Generation" in computer talk provides a framework for the growth of computer industry  based on key technologies developed , Originally , it was used to distinguish between hardware technologies but was extended to include both hardware and software technologies,

The custom of referring to computer era in terms of generations came into wide use only after 1964 .there are totally five computer generations known until today . Below we describe each generations known  along with its identifying characteristics. Although there is some overlap between different generations the approximate  period shown against each is normally accepted .

In the description below , you will come across several new terminologies . Subsequent chapter will deal with these terminologies in details. the idea here  is to provide an overview of the major development and technologies  during  the five generations of computers and not to explain them in details 

Hence this section provides an overview of what al you are going to learn in this entire book.

FIRST GENERATION ( 1942 - 1955 )

The early computer of figure 1.3 and other of their time were manufactured using vacuum tubes as electronic switching device . A vacuum tube [ see Figure 1.4 (a) ]was a fragile glass using filaments as a source of electronics and could control and amplify electronics signals . It was the only high-speed electronics switching devices available in those days . These vacuum tube computers could perform computations in milliseconds and were known as first- generations computers.

Most of the first-generations computers worked on the principle of storing program instructions along with data in memory of computers ( stored program concept ) so that they automatically execute program without human intervention . Memory of these computers used electromagnetic relays , and users fed all data and instructions into the system using punched cards. Programmers wrote instructions in machines and assembly languages because  of work with , only a few specialists understood how to program these early computers.

CHARACTERISTIC FEATURES OF FIRST- GENERATION COMPUTERS ARE AS FOLLOWS :

1. They are the fastest calculating devices of their time. 

2. they were too bulky in size , requiring large rooms for installation.

3. they used thousand of vacuum tubes that emitted large amount of heat and burnt out frequently .Hence , the rooms/area in which these computers located had to be property air-conditioned.

4. Each vacuum tubes consumed about half a watt of power. Since a computers typically used more than ten thousand vacuum tubes, power consumption of these computers was very high.

5. As vacuum tubes used filaments , they had a limited life . Because a computer used thousand of vacuum tube, these computers were prone to frequent hardware failures.

6. Due to low mean time between failures , these computers required constant maintenances.

7. In these computers , thousand of individual components were assembled manually by hand into electronics circuits .Hence , commercial productions of these computers was difficult and costly.

8. Since these computers were difficult to program and use , they had limited commercial use .   

SECOND GENERATION ( 1955-1964 )

 "transistors soon proved to be a better electronics switching devices than vacuum tubes to their following properties ;

1. they were rugged and easier to handle than tubes since they were made of germanium semiconductor material rather than glass. 

2. they were highly reliable as compared to tube since they had no parts like a filament that could burn out. 

3.they could switch much faster ( almost ten times faster ) than tubes .Hence , switching circuits made of  Transistors could operate much faster than their counterparts made of tubes.

4. they consumed almost one-tenth the power consumed by a tube.

5. they were much smaller than a tube .

6. they were less expensive to produce.

7. they dissipated much less heat as compared to vacuum tubes. 

second - generation computer were manufactured using transistors . they were more powerful , more reliable, less expansive , smaller , and cooler to operate than the first- generations computers.

the second generation also experienced a change in storage technology. Memory of second-generations computers was composed of magnetic cores. Magnetic cores are small rings made of ferrite that can be magnetized in either clockwise or anti-clockwise direction. Large random access memory (having storage capacity of few tens of kilobytes) had several magnetic cores strung on  a mesh of wires. 

in 1957 , researches introduced magnetic tape as a faster and more convenient secondary storage medium . Later magnetic disk storage was also developed , and magnetic disk and magnetic tape were the main secondary storage media used in second- generation computers. Users still used punched cards widely for preparing and feeding program and data to a computer.

On software front high level programming languages  ( like FORTRAN, COBAL, ALGOL, AND SNOBOL ) and batch operating system emerged during second generation.  High-Level programing languages made second-generation computers easier to program and use than first - generation computer introduction of batch operating system helped in reducing human intervention while processing multiple jobs resulting in faster processing enhanced  throughput, and easier operation of second-generation computers.

In addition to scientific computations , business and industry users used second - generation computers increasingly for commercial data processing applications like payroll , inventory control , marketing  and production planning .

Ease of use of second-generation computers gave birth to a new profession of programmers and systems analysts in computing that is more oriented towards usage rather than design of computer . this triggered introduction of computer science related course in several college and universities.

CHARACTERISTIC FEATURES OF SECOND- GENERATION COMPUTERS ARE AS AFOLLOWS ;

 1. They were more than ten times faster than the first- generation computers.

2. they are smaller than first-generations and required smaller space . 

3. they consumed less power and dissipated less than the first-generation computer. The rooms /areas in which the second- generation computers were located still required to be properly air-conditioned

4. they were more reliable and less prone to hardware failures than the first-generation computers.

5. they had faster and larger primary and secondary storage as compared to first-generation computers.

6. they were easier to program and use than the first-generation computers. Hence, they had wider commercial use.

7. In these computers, thousand of individual transistors had to be assembled manually by hand into electronics circuits making commercial production of these computers difficult and costly.

THIRD GENERATION ( 1964- 1975 )

In 1958, Jack St. Clair Kilby and  Roberts Noyce invented the first integrated circuit . integrated circuit ( called ICs ) are circuit consisting of several electronics components like transistors , resistors, and capacitors grown on a single chip of silicon eliminating wired interconnection between components. IC technology was also known as " microelectronics" technology because it made it possible to integrate larger number of circuit components into very small ( less than 5 mm  square ) surface of silicon , known as Z "chip" [ see figure 1.4 (c) ] . Initially the integrated circuits contained only about ten to twenty components. This technology was named small- scale integration ( SSI ). Later with the advancement in technology for manufacturing ICs, it because possible to integrate up to about hundred components on a single chip. this technology was known as 

medium scale integration ( MSI ).

Third generation computers were manufacturing using ICs. Earlier ones used SSI technology and later ones used MSI technology.  ICs were smaller , less expensive to produce , more rugged and reliable , faster in operation , dissipated less heat , and consumed less power than circuits built by writing electronics components manually .

Hence, third-generation computers were more powerful, more reliable , less expensive , smaller and cooler to operate than second- generation computers.

Parallel advancements in storage technologies allowed construction of larger magnetic core based random access memory as well as larger capacity magnetic disks and tapes . Hence, third-generation computers typically had few megabytes ( less than 5 Megabytes ) of main memory and disks capable of sorting few tens of megabytes of data per disks drive.

on software front , standardization of high-level of high-level programming language. timesharing operating system unbundling of software from hardware and creation of an independent software industry happened during third generation. FORTRAN and COBOL were the most popular high-level  programming language in those days American National standards Institute  ( ANSI ) standardized them in 1996 and 1998 respectively , and the standardized versions were called ANSI  FORTRAN and ANSI COBOL . The idea was that as long as a programmer follows these standards in program writing. he/she could run his/her program on any computer with an ANSI FORTRAN or ANSI COBOL complier ( see chapter 12 for details ) . Some more high-level programming language were introduced during the third - generation period. Notable among these were PL/1, PASCAL , and BASIC . 

Second-generation computers used batch operating system. in those system, users had to prepare their data and programs and them submit  them to computer center  for processing the operator at the computer center collected . These user job and fed them to a computer in batches at scheduled intervals. The respective users then collected their job's output from the computer center. The inevitable delay resulting from this batch processing approach was very frustrating to some users , especially programmers, because often they had yo wait for days to locate and correct a few program errors. To rectify this situation , John Kemeny and Thomas Kurtz of Dartmouth college introduced the concept of time sharing operating system. Timesharing operating system enables multiple users to directly access and share a computer's resources simultaneously in a manner that each users feels that no one else it using the computer. this  is accomplished by using a large number of independent , relatively low-speed , on-line terminals connected to the computer simultaneously .A separate user  uses each terminals to gain direct access to the computer. Timesharing operating system allocates CPU time in such a way that all user programs have a brief share ( known as a time slice ) of CPU time in turn. Processing speed of CPU allows it to switch from one users  job to another in rapid succession and execute a small portion of each job in allocated time slice until the job is completed. Each user  gets the illusion that he/she alone is using the computer. Introduction of timesharing concept helped in drastically improving the productivity of programmers and made on-line system feasible, resulting in the new on-line application like reservation system, interactive query system , etc.

Until 1965, computer manufactures sold their hardware, along with all  associated software without separately charging for software. For example , buyers received language translators for all language supported on a computer they purchased. From user's standpoint , software was free. However, the situation changed in 1969 when  IBM and other computer manufactures began to price their hardware and software of their need and value For example , now buyers could purchase only the language translators they needed and not all language translators supported on the purchased computer. this led to the creation of many new software houses and the beginning of an independent software industry.

Another important concept introduced during third-generation was that of backward compatibility family of computer During this period, IBM introduced its system 360 as a family of computer with backward compatibility as they were different sizes of mainframe system based on the same machine language. This enabled business to upgrade their computers without incurring costs of replacing  peripheral equipment and modifying program to run on new system. 

Development and introduction of Minicomputer also took place during third-generation. Computer built until early 1960s were mainframe system that only very large companies could afford to purchase and use. Clearly, a need exited for low-cost smaller computers to fill the gaps left by the bigger, faster, and Costlier mainframe system. Several innovators recognized this need and formed new firms in 1960s to produce smaller computer. 

Digital Equipment Corporation (DEC) introduced the first commercial available Minicomputer, the PDP-8 (Programmed Data Processor) , in 1965 . It could easily fit in the corner of a room and did not require attention of a full-time computer operator. It used Timesharing operating system and a number Of users could access it simultaneously from different locations in the  same building. It cost was about one-fourth the cost of a traditional mainframe system making it possible for smaller companies to afford computer. It confirmed the tremendous demand for small computers for business and scientific applications, and by 1971, there were more than 25 computer manufacturers in Minicomputer market. 

CHARACTERISTICS FEATURES OF THIRD-GENERATION COMPUTER ARE AS FOLLOWS: 

1. They were more powerful than second-generation computer. They were capable of performing about 1 million instructions per second. 

2. They were smaller than second-generation computer requiring smaller space. 

3.  They consumed less power and dissipated less heat than second-generation computers. The rooms/areas in which third-generation computers were located still required to be a properly air-conditioned

4. They were more reliable and  less prone to hardware failures than  second-generation computers requiring lower maintenance cost. 

5.  They had faster and larger primary and secondary storage as compared to second-generations computers. 

6.  They were General-purpose machines suitable for both scientific and commercial applications. 

7.  Their manufacturing did not require manual assembly of individual components into electronic circuits resulting in  a reduced human labor and cost involved at assembly stage. Hence, commercial production of these systems was easier and cheaper. However, highly sophisticated technology and expensive setup was required for the manufacture of IC chips. 

8.  Standardization of high-level programming language  allowed program written for one computer to be easily ported to and executed on another computer. 

9.  Timesharing operating system allowed interactive usage and simultaneous use of these system by multiple  users. 

 

10. Timesharing operating system helped in drastically improving the productivity of programmers cutting down the time and cost of program development by several fold. 

11.  Timesharing operating system also made on-line system feasible resulting in usage of these system for new on-line application. 

12.  Unbundling of software from hardware gave users  of these system an opportunity to invest only in software of their need and value. 

13.  Minicomputers of third-generation made computers affordable even by smaller companies. 

                  

FOURTH GENERATION ( 1975- 1989)

Average number o0f electronics components packed on a silicon chip doubled each year after 1965. This progress soon led to the era of large-scale- integration ( LSI ) when it was possible to integrate over 30,000 electronics components on a single chip ,followed by very-large-scale ( VLSI ) when it was possible to integrate about one million electronic components on a single chip .  This progress led to a dramatic development -creation of a microprocessor. A microprocessor contains all circuits needed to perform arithmetic logic and control function , the core activities of all computers, on a single chip , and other support circuity . it started a new social revolution - personal computer ( pc) revolution. Overnight computers became incredibly compact . They became inexpensive to make , and suddenly it became possible for many to own a computer .

By 1978, Apply || from Apply Computer Inc. and the TRS-8 model from the radio Shack Division of Tandy Corporation were dominant personal computer , By 1980, IBM realized that the personal computer market was too promising to ignore and and came out with its 0own  PC in 1981, popularly known as IBM compatible PC or clones. the IBM PC  and its clones became a popular standard for the PC industry during the fourth generation .s

During fourth generation , semiconductor memories replaced magnetic core memories resulting in large random access memories with very fast access time. Hard disks became cheaper , smaller , and larger in capacity. In addition to magnetic tapes, floppy disks became popular as a portable medium for porting programs and data from one computer system to another.

Significant advancements also took place during fourth generation in the area of large-scale computer system. In addition to improved processing and storage capabilities of mainframe systems, the fourth-generation saw the advent of supercomputers based on parallel vector processing and symmetric multiprocessing technologies. A supercomputer based on parallel vector processing technology contains a small number of custom -designed  vector processor which are connected to a number of high-speed data access shared memory modules through a custom-designed , high-bandwidth crossbar switch network . On  the other hand , a supercomputer based on symmetric multiprocessing technology uses commodity microprocessors connected to a shared memory through a high-speed bus or a crossbar switch network . Primary builders of supercomputers of the former category included Cray Research and ETA system , whereas  of the latter category included IBM , silicon Graphics and Digital Equipment Corporation.

High-speed computer networking also developed during fourth-generation . This enabled interconnection of multiple computers for communication and sharing of data among them . Local area network ( LANs ) became popular for connecting computers within an organization or within a campus . Similarly, wide area networks ( WANs ) became for  connecting located at larger distances. this gave rise to network of computers and distributed systems. 

On software front , several new developments emerged to match the new technologies of fourth generation. For example , vendors developed several new operating system for PCs. Notable ones among these were MS-DOS , MS-Window , and Apple's propriety Mac OS. Since PCs were for individuals who were not computer professionals , companies developed graphical users interface for individuals who were not computer professionals , companies developed graphical user interface for making computers more user friendly (easier to use ). A graphical user interface (GUI ) provides icons (picture ) and menus (list of choice) that users can select with a mouse . PC manufacture and application software developers developed several new PC-based application to make PCs a powerful tool . Notable among these were powerful word processing package that allowed easy development of documents , spreadsheet package  that allowed easy manipulation and analysis of data organized in columns and rows, and graphics package that allowed easy drawing of picture and diagram.

Another very useful concept that became popular during fourth-generation was that of multiple windows on a single terminal screen. this feature allowed users to see the status of several applications simultaneously in separate windows on same terminal screen .

In the area of software for large -scale computers, key technologies that became popular included multiprocessing operating system and concurrent programming language. With multiprocessing operating system , a mainframe system could use multiple processor ( a main processor and several subordinate processor ) in such a manner that the subordinate processors could manage the user terminals and peripheral devices , all allowing the main processor to concentrate on processing the main program, improving the overall performance .Supercomputers also used multiprocessing operating system to extract the best performance from that large number of processors used in these system . Concurrent programming language further helped in effectively using the multiprocessing operating system to extract the best performance from the large number of processor used in these system . Concurrent programming languages further helped in effectively using the multiprocessing capabilities of these system by allowing programmers to write their application in such a way that different processors could execute parts of the application in parallel. The most ambitious language of this type was ADA.

During fourth-generation , the UNIX operating system also became very popular foe use on large-scale system .Additionally, due to proliferation of computer networks , several new features were included in exiting operating system to allow multiple computers on the same network to communicate with each other and share resources.

some other software technologies that became popular during fourth - generation are C programming language , object-oriented software design and object-oriented programming. C language combines features of high-level programming language with efficiency of an assembly language. The primary objective of object - oriented- software design are to make programs generalized and to built software systems by combining reusable pieces of program codes called objects. To facilitate object-oriented software design. Several object-oriented programming language were introduced. Out of these , C++ emerged as the most popular object-oriented language.

CHARACTERISTIC FEATURES OF FOURTH - GENERATION ARE AS FOLLOW:

1.  PCs were smaller and cheaper than mainframes or minicomputers of third generation.

2. Although the fourth-generation mainframes and supercomputers required proper air - conditioning of the rooms/ areas in which they were located , no air-conditioning was required for PCs .

3. They consumed less power than third- generation computers .

4. they were more reliable and less prone to hardware failures than third -generation computers requiring negligible maintenances cost.

5. they had faster and larger primary and secondary storage as compared to third generation computers. 

6.  they were general-purpose machines.

7. their manufacturing did not require manual assembly of individual components into electronics circuits resulting in reduced human labor and cost involved at assembly stage . Hence, commercial production of these system was easier and cheaper. however, highly sop0histicated and expensive setup was required for manufacturing LSI and VLSI chips .

8. use of standard high-level programming languages allowed programs written for one computer to be easily ported to and executed on another computer.

9.  Graphical user interface ( GUI ) enabled new users to quickly learn how to use computers. 

10.  PC-based applications made PCs a powerful tool for both office and home  usages.

11.  Network of computer enabled sharing of resources like disks ,printers , etc. among multiple computers and their users. they also enabled several new type of applications involving interaction among computer users  at geographically distant locations. computer supported cooperative working ( CSCW ) . or groupware is one such application in which multiple members working  on a single project and located at distant locations cooperate with each other by using a network of computer.

 

12. In addition to unbundled software, these system also used add- on hardware feature that allowed users to invest only in the hardware configuration and software of their need and value .

13. PCs of fourth generation made computers affordable even by individuals for their personal use at home .

14. Supercomputer of fourth generation enabled parallel of different parts of an application on large number of processor used in these system . This , in turn , enabled running of time - consuming applications much faster .

 FIFTH GENERATION (1989-PRESENT ) :

The trend of further miniaturization of electronic components dramatic increase in power of microprocessor chips, and increase in capacity of main memory and hard disk continued during fifth generation . VLSI technology became ULSI ( ULTRA - LARGE - SCALE INTREGRATION) technology in fifth generation resulting in production of  

microprocessor chips have ten million electronics components. in fact, the speed of microprocessor and the size of main memory and hard disk doubled almost every eighteen month. As a result , many feature found in the CPUs of large mainframe system of third and fourth-generation system became part of microprocessor architecture in fifth generation. This ultimately resulted in availability of very powerful an compact computers becoming available at cheaper rates and death of traditional large mainframe system. Recently processor manufacture started building multicore processor chips instead of increasingly powerful ( faster ) single-core processor chips. The multicore chips improve overall performance by handling more work in parallel.

Due to this pace of advancement in computer technology, we see more compact and more powerful computers being introduced almost every year at more or less the same price or even cheaper. Notable among these are portable notebook computers that give the power of a PC to their users even while travelling. Powerful desktop PCs and work station, powerful servers ,powerful supercomputer , and handheld computers.

storage technology also advanced making larger main memory and disk storage available in newly introduced system. Currently , PCs having few Gigabyte ( GB )of main memory and 80 to 320 Gigabyte (GB) of hard disks capacity are common . Similarly , workstation having 4 to 64 Gigabyte of main memory and few hundred of Gigabyte of hard disk capacity are common. RAID ( Redundant Array of inexpensive Disks ) technology enables configuration of a bunch of disks as a single large disks. It, thus, supports larger hard disk space with better in-built reliability. During fifth generation optical disks ( popularly known as compact Disks or CDs ) emerged as a popular portable mass storage media.

In the area of large-scale system , fifth - generation saw the emergence of more powerful supercomputer based on parallel processing technology. They used multiple processor and were of two type  - Shared memory and distributed memory parallel computers.  In a shared memory parallel computers, a high-school bus or communication network interconnects a number of processor to a common main memory. Whereas in a distributed memory parallel computer, a communication network interconnects a number of processors . each with its own memory, These systems use parallel programming technique to break  a problem into smaller problems and execute them in parallel on multiple processors of the system, Processor of a shared memory parallel computer use memory access mechanism for communication, whereas those of a distributed memory parallel computer use message- passing mechanism for communication. Distributed memory parallel computers have better scalability ( can grow larger in capability ) than shared memory parallel computers, and are now built by clustering together powerful commodity workstation by using a high-speed commodity switched network. This is known as clustering technology.

During fifth generation, the Internet emerged with associated technologies and application. It made it possible for computer users sitting across the globe to communicate with each other within minutes by use of electronics mail ( known as e-mail ) facility. A vast ocean of information became readily available to computer users through the world-wide-web ( known as WWW ).

Moreover ,several new type of exciting applications like electronic commerce, a virtual libraries , virtual classroom, distance education, etc. emerged during the period. 

The tremendous processing power and the massive storage capacity of fifth-generation computers also made them a very useful and popular tool for a wide range of multimedia applications dealing with information containing text, graphics, animation, audio and data video data. In general, data size for multimedia information is much larger than plan text information because representation of graphics, animation ,audio, or video media in digital form requires much larger than that required for representation of plain text .Because of this , multimedia computer system require to play any audio or video associated with a multimedia applications program. The availability of multimedia computer system resulted in a tremendous growth of multimedia applications during fifth-generations.

In the area of operating system, some new concept that popularity during fifth-generation include microkernels , multithreading and multicore operating system. Microkernel  technology enabled designer to model and design operating system in a modular fashion. This make operating system easier to design and implement easier to modify or add new services, and allows users to implement and use their own services. 

Multithreading technology is a popular way to improve application performance through parallelism. Traditional operating system, basic unit of CPU scheduling is a thread. In such operating system, a process consists of an address space containing its instructions and data, and one or more threads sharing same address space. Hence, these systems can create a new thread. switch CPU between threads, and share resources between threads of same process more efficiently than between processes , resulting in faster execution and better overall system performance. A multicore operating system can run multiple programs at the same time on a multicore chip with each core handling a separate program.

In the area of programming language, concept that gained popularity during fifth generation are JAVA programming language , and parallel programming libraries like MPL ( MESSAGE PASSING INTERFACE ) and PVM 

( PARALLEL VIRTUAL MACHINE ). JAVA is used primarily on the World Wide Web . it supports java-based applets allowing web pages to have dynamic information and more interactivity with users of web information. MPI and PVI libraries enable development of standardized parallel programs. So that a programmer can easily port and execute  a parallel program developed for one parallel computer on other parallel computer. MPI is used for distributed memory parallel computers and PVM is used for shared memory parallel computer. 

CHARACTERISTIC FEATURES OF FIFTH-GENERATION COMPUTER ARE AS FOLLOWS :

1.   Portable PCs ( called notebook computer ) are much smaller and handy than PCs of fourth generation allowing users to use computing facility even while travelling .

2.  Fifth-generation desktop  PCs and workstation are several times more powerful than PCs of fourth generation

3.  Although fifth-generation mainframes and supercomputers require proper air- conditioning of the rooms/areas in which they are located, no air-conditioning is normally required for notebook computers, desktop PCs and workstations.

4. They consume less power than their predecessors do.  

5. They are more reliable and less prone  to hardware failure than their predecessors were , requiring negligible maintenances coast .

6.  Many of the large-scale fifth-generation system have hot-plug feature that enables a failed component to be replaced with a new one without the need to shutdown the system . Hence, the uptime of these system is very high.

7.  they have faster and larger primary and secondary storage as compared to their predecessors.

8.  They are general-purpose machines.

9.   their manufacturing does not require manual assembly of individual components into electronics circuits resulting  in reduced human labor and cost involved at assembly stage. Hence, commercial production of these system is easier and cheaper. However , highly sophisticated technology and expensive setup (affordable only by a few organizations in the world ) is required for manufacturing ULSI chips.

10.  Use of standard high-level programming language allows programs written for one computer to be easily ported to and executed on another computer.

11.  More user-friendly interfaces with multimedia features make the system easier to learn and use by anyone , including children.

12.  Newer and more powerful application, including multimedia applications, make the system more useful in every occupation.

13.  Explosion in the size of the internet coupled with internet-based tools and applications have made these system influence the life of even common people.

14.  These system also use the concept of unbundled software and add-on hardware allowing the users to invest only in the hardware configuration and software of their need and value.

15.  With so many types of computers in all price ranges today , we have a computer for almost any type of user whether the user is a child or a world-frame scientist.