First Generation (1940–56)—Vacuum Tubes
Second Generation (1956–63)—Transistors
Third Generation (1964–Early 1970s)—Integrated Circuits
Fourth Generation (Early 1970s–Till Date)—Microprocessors
Fifth Generation (Present and Beyond)—Artificial Intelligence
First Generation (1940–56)—Vacuum Tubes:In these generation vacuum tubes/thermionic valves machines were used which vacuum tubes used for circuitry and magnetic drums for memory.Magnetic drum is a metal cylinder coated magnetic iron oxide material on which data and programs can be stored. The input was based on punched cards and paper tape and the output was in the form of printouts.
Examples: ENIAC, EDVAC and UNIVAC.
Characteristics of First-generation Computers
Second Generation (1956–63)—Transistors:In these generations computers used transistors in place of vacuum tubes, which were superior than vacuum tubes. A transistor is made up of semiconductor material like germanium and silicon. It usually had three leads and performed electrical functions such as voltage, current or power amplification with low power requirements. Since transistor is a small device, the physical size of the computer was greatly reduced. Computers became smaller, faster, cheaper, energy-efficient and more reliable than their predecessors. In second-generation computers, magnetic cores were used as primary memory and magnetic disks as secondary storage devices. However, they still relied on punched cards for input and printouts for output.
One of the most important development in this generation it includes the progress of machine language to assembly language. Assembly language used mnemonics (abbreviations) for instructions rather than numbers; for example, ADD for addition and MULT for multiplication. As a result, programming became less cumbersome. Early high-level programming languages such as COBOL and FORTRAN also came into existence during this period.
Examples: PDP-8, IBM 1401 and IBM 7090.
Characteristics of second-generation computers
Third Generation (1964–Early 1970s)—Integrated Circuits: The development of the integrated circuit was the trait of the third-generation computers. An integrated circuit, also called IC, consisted of a single chip (usually silicon) with many components such as transistors and resistors fabricated on it. Integrated circuits replaced several individually wired transistors. This development made computers smaller in size, reliable and efficient.Instead of punched cards and printouts, users interacted with third-generation computers through keyboards and monitors and interfaced with an operating system. This allowed the device to run many different applications at one time with a central program that monitored the memory. For the first time, computers became accessible to majority of common people because they were smaller and cheaper than their predecessors.
Examples: NCR 395 and B6500.
Third-generation computers have the following characteristics:
Fourth Generation (Early 1970s–Till Date)—Microprocessors:Fourth generation is an Elaboration of third-generation technology. Although, the technology of this generation is still based on the integrated circuit, these have been made readily available because of the development of the microprocessor (circuits containing millions of transistors). The Intel 4004 chip, which was developed in 1971, took the integrated circuit one step further by locating all the components of a computer (central processing unit, memory, and input and output controls) on a minuscule chip. A microprocessor is built onto a single piece of silicon, known as chip. It is about 0.5 cm along one side and not more than 0.05 cm thick.
Fourth-generation computers led to an era of large-scale integration (LSI) and very-large-scale integration (VLSI) technology. LSI technology allowed thousands of transistors to be constructed on one small slice of silicon material, whereas VLSI squeezed hundreds of thousands of components on to a single chip. Ultra-large-scale integration (ULSI) increased that number to millions. This way the computers became smaller and cheaper than ever before.
Examples: Apple II, Altair 8800 and CRAY-1.
Characteristics of Fourth-generation Computers
Fifth Generation (Present and Beyond)—Artificial Intelligence: The dream of creating a human-like computer that would be capable of reasoning and reaching at a decision through a series of 'what-if-then' analyses has existed since the beginning of computer technology. Such a computer would learn from its mistakes and possess the skill of experts. These are the objectives for creating the fifth-generation computers. The starting point of the fifth-generation computers had been set in the early 1990s. The process of developing fifth-generation computers is still in the development stage. However, the 'expert system' concept is already in use. The expert system is defined as a computer system that attempts to mimic the thought process and reasoning of experts in specific areas. Three characteristics can be identified with the fifth-generation computers. These are as follows:
Mega Chips: Fifth-generation computers will use super large-scale integrated (SLSI) chips, which will result in the production of microprocessor having millions of electronic components on a single chip. To store instructions and information, fifth-generation computers require a great amount of storage capacity. Mega chips may enable the computer to approximate the memory capacity of the human mind.
Parallel Processing: Computers with one processor access and execute only one instruction at a time. This is called serial processing. However, fifth-generation computer will use multiple processors and perform parallel processing, thereby accessing several instructions at one time and working on them at the same time.
Artificial Intelligence (AI): It refers to a series of related technologies that tries to simulate and reproduce human behaviour including thinking, speaking and reasoning. AI comprises a group of related technologies: expert systems (ES), natural language processing (NLP), speech recognition, vision recognition and robotics.