SECOND GENERATION COMPUTERS (ERA OF TRANSISTORS) 1956 - 1964

ERA OF TRANSISTORS Transistors replaced vacuum tubes and ushered in the second generation computers. Transistors are devices composed of semi conductor material that amplifies, opens and closes a circuit. Invented in 1947 by three scientists working at AT & T Bell Labs (John Bardeen, William Shockley and Walter Brattain). Today’s micro processors contain millions of microscopic transistors.

DISADVANTAGES OF VACUUM TUBES Required a great deal of space Needed to be replaced more often. ENIAC computers for example had 18000 vacuum tubes in them; think of the cost of housing and cooling the system. The transistor had solved all these problems.

CHARACTERISTICS OF 2ND GENERATION COMPUTERS Become smaller and Faster (increased processing speed) Cheaper in terms of production and maintenance (produced less heat and therefore minimal time for break downs) More energy efficient and reliable (due to better circuitry) First computers to store instructions in memory --- moving away from magnetic drums Employed assembly language Employed Assembly language rather than Machine language employed in the 1st generation computers. They started to show characteristics of modern computers The instructions (programs) could be stored inside the computer memory. High level languages such as COBOL and FORTRAN were used for programming.

Machine Language: Languages understood by the machine (almost impossible for humans to understand) High Level or Assembly Languages: Assembly language contains the same instructions as a machine language, but the instructions and variables have names instead of being just numbers. High-level languages are translated into assembly language or machine language by a compiler. Assembly language programs are translated into machine language by a program called an assembler.

1st COMPUTER BUG Among other developments in this generation was the founding of the first computer bug by GRACE MURRAY HOPPER She found a moth stuck in a relay which was responsible for a malfunction; she ultimately called it DEBUGGING a computer.

THIRD GENERATION: THE ERA OF INTEGRATED CIRCUITS (1964 – 1974) Integrated circuits are defined as a single chip that has thousands (or even millions) of transistors, resistors and capacitors integrated together. Placing a large number of transistors onto a single chip significantly improved the speed or power of a single computer and lowered its cost.

CHARACTERISTICS OF THIRD GENERATION COMPUTERS Smaller computers compared to 2nd generation machines User interaction with the help of the operating system, keyboard and mouse Multi-tasking (allowing the computer to run different applications at the same time) Magnetic tape and Disks replaced Punched cards as a medium for input and output) Consumed less power compared to the previous generation computers

FOURTH GENERATION: THE ERA OF THE MICROPROCESSOR (1971 –TO DATE This generation saw the largest scale integration of computer circuitry. It is characterized by two principles: development of monolithic integrated circuits (thousands or millions of transistors put onto a single integrated circuit) and the invention of the microprocessor (a single chip that could do the processing of a full scale computer).

Microprocessors can as well be defined as integrated circuits that can interpret, execute program instructions and handle arithmetic operations. This makes 4th generation computers the fastest, smallest and most powerful. Earliest chips developed was the INTEL 4004 Chip developed in 1971

MICROPROCESSORS Microprocessors are a defining trait of computers today, and therefore to choose the best computer for your needs, you must know their different characteristics. CLOCK SPEED (CLOCK RATE) It’s the speed at which a microprocessor executes instructions. Every computer contains an internal clock that regulates the rate at which instructions are executed and synchronizes all the various computer components

Clock speed is stated or measured in either MHz or GHz Clock speed is stated or measured in either MHz or GHz... 1 MHz (MEGAHERZ) is equal to 1 million cycles per second, while 1 GHz (GIGAHERZ) is equal to 1 billion cycles per second. HERZ refers to cycles per second. At present most microprocessors run from 1.8GHz to 3.2 GHz.

Instruction set is the second characteristic of microprocessors Instruction set is the second characteristic of microprocessors. All possible operations that can be performed by the microprocessor are based on the set of its instruction set. Advanced processors may have more 150 or 200 instruction sets and therefore can have extremely advanced or complicated tasks. Pentium 5 has a bigger instruction set than Pentium 4 machines.

CACHE MEMORY It refers to the high speed storage mechanism that holds recently read data and instructions from the main memory. Most programs access the same information repeatedly while running. This eliminates the processor from having to constantly access the main memory which may slow down the computer system.

BUS SPEED Bus speed refers to how many times data can be transferred over the system Bus per second. It’s measured in MHz (the same unit used to measure the clock speed). The processor usually communicates with other devices through the DATA BUS. While a processor might be working at up to 3 GHz, quite often the performance of the computer is hampered by a slower data bus speed.  Data bus speeds range from 200MHz up to 1GHz.

Examples of the earliest 4th generation computers Altair 8800 computer kit in 1975 Apple 2 in 1977 PC from IBM in 1981 In summary, 4th generation computers are associated with the following characteristics; use of microprocessors, large scale integration of computer parts, saw the development of sophisticated operating systems and more friendly programs, introduction of computer networks, development of Graphical User Interfaces (GUI) to name a few. Computers became more powerful and were applied in many spheres of life.

FIFTH GENERATION: THE ERA OF ARTIFICIAL INTELLIGENCE (PRESENT AND BEYOND) Also known as the future computer generation, such computing devices are based on the principle of Artificial Intelligence and are a rapidly growing technology that is being researched and applied worldwide.

ARTIFICIAL INTELLIGENCE Artificial intelligence is a field whose major thrusts are to develop intelligent computer power to supplement human brain power, and to better understand how we think, reason and learn. Artificial Intelligence is therefore a branch of computer science concerned with making computers behave like humans, with characteristics such as self diagnosis and healing, self organizing, visual and audio input and output and learning from experience.

Various applications of Artificial Intelligence are being developed every day. These include; Expert Systems, Natural Language Understanding Systems, Speech Recognition and Understanding Systems, Robotics, and Computer Vision. John McCarthy coined the term Artificial Intelligence in the late 1950s ---- and the biggest question of the day then, was, “what possesses something to have artificial intelligence?” Intelligence refers to the capacity to acquire and apply knowledge, while knowledge is defined as familiarity, awareness or understanding gained through experience or study. Artificial Intelligence is the ability to acquire and apply an understanding gained through experience or study in order to mimic "natural intelligence." This is, in fact, what expert systems are being designed to do.

LIMITATIONS OF ARTIFICIAL INTELLIGENCE “What makes an expert system seem not truly intelligent? With today's technology, there are a number of limitations of expert systems that might make expert systems appear to some to be "artificially stupid."

Ability to possess and use common sense Development of deep reasoning systems Ability to vary an expert system's explanation capability Ability to get expert systems to learn Ability to have distributed expert systems Ability to easily acquire and update knowledge

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