FOURTH GENERATION COMPUTER

The period of Fourth Generation was 1972-1990.

The fourth generation of computers is marked by the use of Very Large Scale Integrated (VLSI) circuits.VLSI circuits having about 5000 transistors and other circuit elements and their associated circuits on a single chip made it possible to have microcomputers of fourth generation. Fourth Generation computers became more powerful, compact, reliable, and affordable. As a result, it gave rise to personal computer (PC) revolution.

In this generation Time sharing, Real time, Networks, Distributed Operating System were used

. All the Higher level languages like C and C++, DBASE etc. were used in this generation

The main features of Fourth Generation are

• :  VLSI technology used
•   Very cheap 
•  Portable and reliable 
•  Use of PC's
•  Very small size
•   Pipeline processing 
•  No A.C. needed
•  Concept of internet was introduced
•   Great developments in the fields of networks
•   Computers became easily available

 Some computer of this generation were

• :  DEC 10 
•  STAR 1000 
•  PDP 11
•  CRAY-1(Super Computer)
•   CRAY-X-MP(Super Computer)
• 
  

The fourth generation of computer technology is based on the microprocessor. Microprocessors employ Large Scale Integration (LSI) and Very Large Scale Integration (VLSI) techniques to pack thousands or millions of transistors on a single chip.

The Intel 4004 was the first processor to be built on a single silicon chip. It contained 2,300 transistors. Built in 1971, it marked the beginning of a generation of computers whose lineage would stretch to the current day.

In 1981 IBM selected the Intel Corporation as the builder of the microprocessor (the Intel 8086) for its new machine, the IBM-PC. This new computer was able to execute 240,000 additions per second. Although much slower than the computers in the IBM 360 family, this computer cost only $4,000 in today's dollars! This price/performance ratio caused a boom in the personal computer market.

In 1996, the Intel Corporation's Pentium Pro PC was able to execute 400,000,000 additions per second. This was about 210,000 times as fast as the ENIAC–the workhorse of World War II. The machine cost only $4,400 in inflation-adjusted dollars.

Microprocessor technology is now found in all modern computers. The chips themselves can be made inexpensively and in large quantities. Processor chips are used as central processors and memory chips are used for dynamic random access memory (RAM) . Both types of chips make use of the millions of transistors etched on their silicon surface. The future could bring chips that combine the processor and the memory on a single silicon die.

During the late 1980s and into the 1990s cached, pipelined, and superscaler microprocessors became commonplace. Because many transistors could be concentrated in a very small space, scientists were able to design these single chip processors with on-board memory (called acache ) and were able to exploit instruction level parallelism by using instruction pipelines along with designs that permitted more than one instruction to be executed at a time (called superscaler). The Intel Pentium Pro PC was a cached, superscaler, pipelined microprocessor.

Also, during this period, an increase in the use of parallel processors has occurred. These machines combine many processors, linked in various ways, to compute results in parallel. They have been used for scientific computations and are now being used for database and file servers as well. They are not as ubiquitous as uniprocessors because, after many years of research, they are still very hard to program and many problems may not lend themselves to a parallel solution.

The early developments in computer technology were based on revolutionary advances in technology. Inventions and new technology were the driving force. The more recent developments are probably best viewed as evolutionary rather than revolutionary.

It has been suggested that if the airline industry had improved at the same rate as the computer industry, one could travel from New York to San Franscisco in 5 seconds for 50 cents. In the late 1990s, microprocessors were improving in performance at the rate of 55 percent per year. If that trend continues, and it is not absolutely certain that it will, by the year 2020 a single microprocessor could possess all the computing power of all the computers in Silicon Valley at the dawn of the twenty-first century.

see also Apple Computer, Inc.; Bell Labs; Eckert, J. Presper, Jr. and Mauchly, John W.; Integrated Circuits; Intel Corporation; Microsoft Corporation; Xerox Corporation.