1.1.ย ย ย ย History of Computers When the human race started doing some trade, it felt a need for a calculating device. The first calculating device, which was used 2000 years ago was called abacus and the improvements in the calculating device in that age were slow. The next change came after about 1600 years. Following this, the changes were frequent and the mechanical desk calculator was developed around 1800 A.D. In ย 1833, Prof. Charles Babbage, the father of the computer, developed a machine called analytical engine which was the vase for the modern digital computer. 1.2ย ย ย ย ย Generation of Computers 1.2.1ย ย Computer generations First generation computers (1946-1956) They made use of vacuum tubes to store and process information. The tubes consumed a lot of power and generated a lot of heat (overheating). They were huge in size and occupy a room. They used magnetic tape. Storage capacity was very low i.e. 2kb and speed of processing was also very low. First machine in this category was ENIAC (electronic discrete variable automatic computer) and later came UNIVAC (universal automatic computers).these computers were mostly computational machines. Their input /output capabilities were usually limited to the keyboard and or punched card input and printer and or punched cart output. The speed of these machines was described in milliseconds (1/1000 of a second) Second generation computers (1957-1967) These computers used transistors after invention of transistors. The transistor is smaller cheaper and produced less heat than vacuum tubes and consumed less power. The cost of computers decreased and the speed increased. The second generation saw the introduction of more complex ALU and CPU, the use of high level languages and provision of system software with the computer. Data access time was measured in micro-seconds. Removable disk storage units were developed for use on these machines. The speed of these machines was described in microseconds (1/1000, 000 of a second). These computers had programming languages whose vocabularies are close to the human natural language, English language. Third generation computers (1965-1980) Introduced the use of very small electronic circuit called integrated circuits (IC) by combining several transistors together between 3 transistors to make 1 IC. With IC you can house thousands of transistors in one IC. This change further decreasedย ย the ย size,ย ย heat ย output ย and ย theย ย maintenance ย complexity ย of ย the computers while increasing its speed. The small circuitry that resulted improved the processing speed i.e. 10 times the past. The speed of these machines was described in nanoseconds (1/1,000,000,000 of a second). They have higher main memory capacity, reliable and increased processing power (have the capability of holding more than one set of instructions and operate on them) than the second generation computers. Invention of IC revolutionalised electronics and started the error of micro-electronics. The IBM 360 is an example of third generation computers. Fourth generation computers (1980s) Use large scale integration circuits which housed hundreds of transistors and very large IC which are between 200,000 to 400, 000 in one IC. Memory used includes magnetic disc and optical disc. Memory size expanded up to several MB and speed was 10 times faster. This generation marked the origin of mini computers in use today. Fifth generation computers (1990-current) The design of these computers was based on VLSI (very large scale integration) technology, the micro chip technology that gave rise to the smaller computers known as the micro computers in use today. These computers are used in networking .examples of micro computers are IBM PCs BBC micro etc. the micro computers are usually described as PCs or stand alone or desktop computers because they were designed primarily to serve single person at a time. The fifth generation is still a state of the art technology that relies on predictions and further technological refinements. Summary Research shows that the trend in computer technology revolution is that there is; Continual decrease in computer size Improved speed and power processing Decrease in computers and the related facilities cost Number of components in computer per circuit (IC) greatly increased over 500,000 ย physical ย elements ย e.g. ย transistors, ย capacities, ย diodes ย etc ย per chip(IC). 1.3ย ย ย ย ย Characteristics of Computers Speed โ a computer is a very fast machine. It can perform in a very few seconds the amount of work that a human being can do in a year if he/she worked day and night doing nothing else. Accuracy โ the computer accuracy is consistently high. Diligence โย computers are free from monotony, ย tiredness and lackย of concentration etc. ย It can thereforeย work for hours without creatingย an error. For example if 10 million calculations are to be done, a computer will do the tenth million calculations with exactly the same speed and accuracy as the first one. Versatility โ ย a ย computer ย performs ย various ย tasks ย with ย ease. ย I.e. ย it ย can search for a letter, the next moment prepare an electricity bill, and write a report next then do an arithmetic calculation all with ease. Power of remembering โ a computer can store and recall any information due to its secondary storage capability. No intelligence ย Quotient ย (IQ) ย โ ย a ย computer ย cannot ย make ย its ย own decisions and has to be instructed on what to do. No feelings โ computers are devoid of emotions. They have no feelings or instincts and none possesses the equivalent of a human heart and soul. 1.4ย ย ย ย ย Basic Computer Concepts Definition of a computer A computer is an electronic device capable of executing instructions, developed based on algorithms stored in its memory, to process data fed to it and produce the required results faster than human beings. The definition from the ย Merriam-Webster Dictionary : “one that computes; ย specifically : a programmable electronic device that can store, retrieve, and process data” 1.5ย ย ย ย ย Types of Computers What different types of computers are there ? This categories are based on size, price and capabilities Super computers They are very large in size and use multiple processors and superior technology. Super computers are biggest in size, the most expensive in price than any other is classified and known as super