Basic Concepts in Computer Science PDF

**Basic Concepts** **1.0 Introduction** In the 21^st^ century, computers have become indispensable tools in virtually all aspects of human lives. The development of handheld computers such as personal digital assistants (PDAs), tablet computers and smart phones has helped computers to become ubiqu...

**Basic Concepts** **1.0 Introduction** In the 21^st^ century, computers have become indispensable tools in virtually all aspects of human lives. The development of handheld computers such as personal digital assistants (PDAs), tablet computers and smart phones has helped computers to become ubiquitous. This unit presents background information about computers by defining basic computer terms, providing a brief history of modern computing, and describing the parts of a computer system. **1.1 BRIEF HISTORY OF COMPUTING** A digital computer unlike the analogue computer and hybrid computers represents data by a coded set of discrete electrical pulses. The computer system as presently structured has passed through several stages of conceptual development including: I. The invention of ABACUS (otherwise called BEAD FRAME) in china around the 7th century B.C. The ABACUS was for addition. II. The design of a logarithmic scale by the Scottish mathematician John Napier(1550-1617) in the 17^th^ century A.D III. The inventory of the slide rule 1620 by the English mathematician Edmund Gunter (1581-1626). IV. French mathematician Blaise Pascal (1624-1662) who invented a mechanical calculator in 1642. V. Sir Samuel Morland (1625-1695), an English mathematician who invented three calculating machines between 1663 and 1666 VI. German philosopher and mathematician Gottfried Leibnitz (1646-1716) who in 1671 developed a calculator for multiplication and division. VII. J.M.Jacquard a French weaver, in 1801 developed the punched cards. VIII. Charles Babbages (1792-1872) the English mathematician who is regarded as the Father of Computing.He it was who first made an attempt to design a machine different from hand calculator. His still-born machines were called "Difference Engine"(Which he started designing in 1823) and "Analytical Engine". IX. American Statistician Hermann Hollerith(1860-1929) who in the 1880s started to develop equipment and procedure for handling census data after being commissioned for the work by the United State Bureau of the census. X. British Mathematician George Boole (1815-1864) who in the late1853 published a paper entitled "An investigation of the Laws of Thought". The mathematician theories of logic and probability are founded on these laws. His algebraic theory is now widely known as "Boolean Algebra" XI. The British mathematician Alan Turing who in 1936 proposed a test for determining whether a machine can think. This lead to the theoretical concept known as "Turing machine". XII. J.W. Mauchly and J.P. Eckert, two American Engineers who in 1939 designed the ENIAC (Electronic Numerical Integrator and Calculator). XIII. Howard Aiken, American mathematician who in 1944 invented a fully automatic calculator after seven years of work XIV. M.V. Milkes, an Englishman, who in 1949 built the first stored program computer called EDSAC (Electronic Delay Storage Automatic Computer) at Cambridge University. XV. The Hungarian-born American mathematician john Von Neuman (1903-1957) and the American mathematician Herman Goldstine and A,W, Burks who in the series of historic reports written between 1946 and 1949 (inclusive) consolidated the stored program concept of computer architecture. They were responsible for laying down the design plan for the present day computers. This design plan is sometimes referred to as the Von Neumann architecture. Their work which was carried out in the Institute for Advanced Study Princeton, New jersey, USA is considered as the most important contribution to the development of modern computers XVI. The development of EDVAC (Electronic Discrete Variable Computer) **1.2 Definition of Terms** **What is computer science?** Computer science is the study of computers and computational system. **Computer**: A computer system is an automatic electronic data processing system in the sense that it collects, manipulates, distributes, facts and figures by electronic means in order to achieve a desired output. Computer can also be define as An electronic device, operating under the control of instructions stored in its own memory that can accept data (input), process the data according to specified rules, produce information (output), and store the information for future use. Functionalities of a computer: Any digital computer carries out these functions in gross terms: i. Accept data through an input device (e.g. keyboard or mouse) ii. Process the data to convert it into information iii. Display the information on an output device (e.g. visual display unit or printer) iv. Store the information for future use in a storage device (e.g. hard disc or compact disc) **Data:** Data refer to raw or unprocessed facts about a person, place or thing. Examples of data include name, age, height and profession. Data is the plural for datum. **Information:** Information is processed data or data that has been converted into useful form e.g. the result of students in an examination or the net pay of an employee. Based on the component structure of the modern computer, at least four generation of computers have up till the 1980s emerged. **1.3 CLASSIFICATION OF COMPUTERS** There are various ways by which computers are classified, the major ones are based on the following: 1. Technological innovation. 2. Manner/method of data representation. 3. Purpose of the computer. 4. Processing speed. **CLASSIFICATION BASED ON TECHNOLOGICAL INNOVATION** Classification of computers based on technological innovation involves the grouping of computers in terms of their various generations i.e. stages of computer development. These various generations of computers were triggered by the work of inquisitive researchers who took it upon themselves to correct the mistakes or laxities in their previous discoveries at one particular time or the other. Such generations of computers are as follows: **FIRST GENERATION OF COMPUTERS (mid1940s-1950s)** These are the computers that were in use in the early 1950s.The technological innovation that led this group of computers was the **Stored Program Concept**. The logic part of these computers was made of **Vacuum Tubes** while **Magnetic Drum** was used for the memory element. Because of the vacuum tubes, first generation computers were very large, expensive and consumed a lot of electricity hence generates a lot of heat. Examples of the first generation computers are EDVAC, UNIVAC and IBM700 series. **CHARACTERISTICS OF THE FIRST GENERATION COMPUTERS** As a result of the vacuum tube used in this generation of computers, the machines possess the following features: 1. They are very large in size. 2. They consume a lot of electricity, hence generates a lot of heat. 3. They are usually very expensive to maintain. 4. The memory element was made up of magnetic drum. 5. The programs were written in Machine Language. C:\\Users\\user\\Pictures\\first generation.png **SECOND GENERATION OF COMPUTERS (late1950s-mid1960s)** This group of computer came about to correct or to reduce the problems of the first generation computers. The invention of **Transistor**- a solid-state conductor made this generation of computer possible. The transistors replaced the vacuum tubes as the logic circuit and because the transistor is a solid-state device, computers processing speed became faster and the system became smaller in size compare to the first generation computers was however retained. Examples of computers in this generation are UNIVAC 1107, IBM 7030 and IBM 7090 series. **CHARACTERISTICS OF THE SECOND GENERATION COMPUTERS** 1. The logic part of computers in the generation was made up of transistors. 2. The memory element i.e. the Magnetic drum was however retained. 3. The size is also reduced compared to the size of the first generation of computers. 4. They consume less electricity hence produce less heat. 5. Assembly language was used for the programming of these computers.  **THIRD GENERATION OF COMPUTERS (mid 1960s-1970)** The technological invention that led to this generation of computers is the **Integrated Circuit(IC).** An integrated circuit consists of complex electronic circuits fabricated on a single chip not more than two millimeters long. This reduced the size of the computers. They were also faster than the computers of the previous generations. This generation of computers used cheap **Metal Oxide Semiconductor (MOS)** for their memory element. It was in this generation of computers that high-level languages were introduced. Examples of computers in this generation are PDP-11, CDC 6600, and CDC 7600 among others. **CHARACTERISTICS OF THE THIRD GENERATION COMPUTERS**. 1. The memory element was made up of Metal Oxide Semiconductors. 2. Small Scale and medium scale integrated circuit formed the logic part 3. Computers in this generation were able to process more than one task at a time (i.e. Multi- processing ability). 4. High-level language were introduced.. 5. Operating system was also introduced in this generation. 6. These computers were faster than the previous ones. 7. Keyboard is used as input device 8. Monitor and printouts are used for output Users interacted with the third generation computers through an operating system, which allowed the device to run many different applications at one time with a central program that monitored the memory. Computers for the first time became accessible to a mass audience C:\\Users\\user\\Pictures\\intergrated circuit.png **FOURTH GENERATION OF COMPUTERS (1971)** The technological innovation that led to this generation of computers is the **Very Large Integrated Circuit** of the microprocessor. A microprocessor is a central processing unit fabricated on a single silicon chip. It worth nothing that the integrated circuit mentioned above is a small-scale integration compared to the very large scale integration of the microprocessor. In fact, the introduction of microprocessors marked the beginning of varieties of application software such as the word processing and desktop publishing packages. Examples of computers in this generation are IBM 3033, Burroughs B7700 and mainframes. **CHARACTERISTICS OF THE FOURTH GENERATION COMPUTERS.** 1. Microcomputers were introduced due to the small size of microprocessors. 2. Computer became faster compared to those of the previous generation. 3. High-level languages were also used for programming this generation of computers. 4. Varieties of software application into this generation of computers.  **FIFTH GENERATION OF COMPUTERS** Despite the aforementioned generations of computers new innovations are constantly springing up. This makes strict classification based on technological innovations almost impossible. In fact, under such new innovation of computer it is expected that normal or present computer architectures it expected that normal or present computer architecture of **Von Neumann model** would be emphasized. Computers would be data driven. It is also hoped that **Artificial Intelligence (AI)** will play a major role especially in the area of software development. A good example of the 5^th^ generation computers are some special purpose computers like Robots find in departmental stores and other electronic machines designed for the purpose of assisting human being in business as well as house chores. **CHARACTERISTICS OF THE FIFTH GENERATION COMPUTERS** 1. Very Large Integrated Circuit is used for the logical part. 2. The software of such computers is highly characterized with Artificial Intelligence. 3. Computers in this generation perform virtually all things. The **sixth generation** of computers came into being in the late **1990s.** The architecture is based on neural networks. C:\\Users\\user\\Pictures\\Artificial intelligence.png **1.4 CLASSIFICATION BASED ON METHODS OF DATA PRESENTATION** Computers can also be classified according to the manner of data representation as follows: 1. Digital computers. 2. Analogue computers. 3. Hybrid computers. Digital Computers: These are computers that records data by counting in discrete variables which corresponds to ''on'' and ''off'' states of electricity. They can only be used for the purpose of arithmetic. It is highly used for addition, subtraction, division and comparison purposes. They are often used at homes, offices, factories, and shops. Digital computers. Are either general or special purpose computers. Examples are calculator and adding machines. Analogue Computers: These are computers, which records data by using physical quantities in proportion to a given amount of number. They are used mainly for measurement for example thermometer used for measuring temperature. Hybrid Computers: These are computers, which imbibed the concepts and qualities of both digital and analogue computers e.g. Microcomputers. **1.5** **CLASSIFICATION BASED ON PURPOSE** Computers can also be classified based on the nature of purpose for which they are made. These mainly consists of two; General purpose computers and Special Purpose computers. General Purpose Computers: General purpose computers are those computers which can be programmed and used for a variety of tasks. They are computers that are made for no special purpose and can be used for multiple tasks. Special Purpose Computers: Special purpose computers on the other hand are those which are specially designed for a specific reason and have programs already hardwired to suit the specific task for which they are made. Hence they are not programmable. Examples of special purpose computers include those specially made for research and navigation purposes among others.