Fourth generation of Computer

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Fourth Generation of Computer (1975-1990):

1. First Decade (1976-1985)

The fourth generation may be identified by the advent of the microprocessor chip. Medium scale integrated circuits progressed to Large and Very Large Scale Integrated (VLSI) circuits packing about 100,000 transistors in a chip. Magnetic core memories were replaced by semiconductor memories. Semiconductor memory sizes of 16 MB with a cycle time of 200 ns were in common use. The emergence of the microprocessor led to two directions in computer development. One direction was the .emergence extremely powerful personal computers. Computer cost came down so rapidly that professionals had own computers to use in their office and home. Hard disks provided a low cost, high capacity secondary memory.

A development which was to have a major impact on the history of computing was the decision of IBM to make the architecture of IBM Personal Computer (IBM PC) open and use non-proprietary processor (Intel 8008). Another concurrent decision was to outsource the development of the Operating System of IBM PC to a new company called the Microsoft. Microsoft negotiated with IBM a non-exclusive agreement permitting it to license the OS to anyone. Microsoft first developed a very small OS called MS-DOS (Microsoft Disk Operating System) which was a successor of a system called CP/M (Control Program for Microcomputers).

The open architecture of IBM PC allowed many small companies to make PCs, conforming to IBM’s architecture, using off-the-shelf Intel microprocessors. These were called IBM clones. All these IBM clone manufacturers licensed their OS from Microsoft. This had a far-reaching consequence on the proliferation of IBM PCs, dominance of Microsoft as an OS vendor and emergence of a number of application software developers who could design applications using MS-DOS (which was becoming a de facto standard) for IBM PCs and their clones. A large number of applications such as word processors, spreadsheets and database management systems for PCs emerged. IBM PC soon became a common office machine on everyone’s desk replacing typewriters.

The other direction of development was the decentralization of computer organization. Individual microprocessor controls for terminals and peripheral devices allowed the CPU to concentrate on processing the main program. Networks of computers and distributed computer systems were developed. Disk memories became very large (1000 MB/drive). A significant progress in software was the development of concurrent programming languages. Such languages are important to program development of concurrent programming languages. Such language of this type was ADA. Another important development was interactive a graphic devices and language interfaces to graphic systems. The emergence of graphics gave a great impetus to computer-aided engineering design.

Fourth generation saw the coming of age of UNIX OS and time shared interactive systems. These systems became user-friendly and highly reliable. The effective cost of computing came down. Computers also began to be used widely.

2. Second Phase (1986-2000)

The second phase of the fourth generation has seen a relentless increase in the speed of microprocessors and the size of the main memory. The speed of microprocessors and the size of the main memory and hard disk went up by a factor of 4 every 3 years. Many of the features originally found in CPUs of large expensive main frame computers of the first decade of the fourth generation because part of the microprocessor architecture in the 1990s. Thus, the mainframe computer of early 1980s died in mid-1990s. The alpha microprocessor chip designed by DEC in 1994 packed 9.3 million transistors in a single integrated circuit, was driven by a 300 MHz clock, and could carry out a billion operations per second. It had built-in cache memory of 64 KB and 32 registers to store temporary operands. Apart from this IBM, Apple computers and Motorola cooperated in designing a microprocessor called Power PC 600 series. Intel also designed a powerful chip in 1990s called Pentium with MMX (Multimedia Extension) and Pentium 11 with a clock speed of 466 MHz and a Celeron processor with a 300 MHz clock. In 2000, Intel introduced a 64-bit processor called IA-64 or Itanium.
Microprocessors such as Pentium and Power PC are being used as the CPU of Personal computers and portable laptop and hand-held computers. Desktop workstations and powerful servers for numeric computing, as well as file services, used RISC microprocessors such as Alpha, MIPS and SUNSPARC.
The area of hard disk storage also saw vast improvements. 1 GB disk on workstations became common in 1994. For Large disks, RAID technology (Redundant Array of Inexpensive Disks) was used to give storage of 100 GB. Optical disks also emerged as mass storage, particularly for read only files.
Optical storage sizes were of the order of 650 MB on a 5.25” disk. New optical disks known as Digital Versatile Disk ROMs (DVDROMS) with the maximum storage capacity of around 17 GB emerged around 1998. Writable CDs were developed around the same time. The availability of optical disks at low cost saw the development of multimedia applications. Multimedia workstations were widely used.
Computer Networks came of age. The networks became very powerful with the advent of fibre optic Local Area Networks which could transmit 100 MB/s to 1 GB/s. Many mainframes were replaced by powerful workstations connected by a fibre optic network. Another major event during this phase was the rapid increase in the number of computers connected to the Internet. This led to the emergence of the World Wide Web which eased information retrieval. The Internet also brought out the need to execute programs on a variety of computers. This led to the emergence of a new object oriented language called Java. Applications written in Java, called Java applets, could be glued together with software called Java script to create large programs.
In the area of languages, C language became popular. This was followed by a new method of design called the object oriented design. The primary objectives of object oriented design were to generalize programs and to reuse objects. The C++ language emerged as the most popular object oriented language. One also saw a trend towards design of specification oriented languages. PROLOG was designed for logic oriented specification language and Haskell, ML, etc. as functional specification oriented languages. With the emergence of distributed computers connected by networks, considerable effort has gone into programming distributed systems. A variety of parallel computers were built, but no commonly accepted standard parallel programming language emerged.

The characteristic features of fourth-generation computers are as follows:

        1. Their manufacturing did not require manual assembly of individual components into electronic circuits, resulting in 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 LSI and VLSI chips. The Large Scale Integrated Circuits (LLI) and the very scale integrated circuits (VLSI) are used in the fourth generation of computer.

         2 .The computers become easily available in this generation.

         3. No AC required when we use the computer of the fourth generation.

 4. We have great development in the field of computer network during the fourth generation.

        5. They had faster and larger secondary storage as compared to third-generation computers.

        6. The computers of the fourth generation is high- level programming languages allowed program    written from one computer to another computer easily were portable and reliable.

7. These computers are very cheap and very small than mainframes or mini computers of the third generation.

8. The computers of the fourth generation were used in pipeline processing.

9. The concept of the internet was introduced in this generation of computer.

10. We can use personal computers in the fourth generation of computers.

11. Graphical User Interface enabled new users to quickly learn how to use computer.

12. PC based applications computers in the fourth generation made the PCs more use office and home usage is a powerful tool affordable even by individual also.

13. Network Of computers enabled sharing of resources like disks, printers, etc. among multiple computers and their users. They also enabled several new types of application involving interaction among computer users at geographically distant locations. Computer Supported Cooperative Working (CSCW), or groupware is one such locations, cooperate with each other, by using a network of computers.

Some computers of this generation are given below:

1. DEC10.
2. STAR 1000.
3. PDP11.
4. CRAY-1(Supercomputer).
5. CRAY-X –MP (supercomputer).
6. IBM PC/AT

The Advantages of the fourth generation:

1. These computers are used for the general purpose.
2. There is no need for the air conditioner when we use the computer of the fourth generation.
3. The computer of the fourth generation was more reliable than the previous generation.
4. These computers can perform the calculation of data in picoseconds.
5. The computer of the fourth-generation consumed less electrical power as compared to the previous generation of computer.
6. The heat generation is less as compared to the previous computer.
7. The maintenance cost is very low in the fourth generation of computer.
8. These computers are microprocessor-based systems.
9. The memory storage is increased in the computers of the fourth generation.
10. The processing power and speed have increased in these computers.
11. The sizes of peripheral devices become small in the fourth generation.
12. The networking features were developed in the computers of the fourth generation.
13. The output was more reliable and accurate now in these computers.
14. These computers are less need to repair.
15. The computers of the fourth-generation are mainly used for commercial production.

The disadvantage of the fourth generation: 

      1. The latest technology is needed for the manufacturing of microprocessors. 

      2.  Highly sophisticated and costly technology was required to manufacture the LSI and VLSI chips.