Cos 111 1st PDF

# Introduction A computer is a tool or machine used for processing data to give required information. It is capable of: - taking input data through the keyboard - storing the input data in a diskette, hard disk or other medium - processing it in the central processing unit - giving out the result...

# Introduction A computer is a tool or machine used for processing data to give required information. It is capable of: - taking input data through the keyboard - storing the input data in a diskette, hard disk or other medium - processing it in the central processing unit - giving out the result on the screen or the Visual Display Unit ## Schematic Diagram | | | | |--------|--------|--------| | INPUT | PROCESSING | OUTPUT | | (DATA) | | (INFORMATION) | ## Definitions - **Data:** refers to facts about a person, object, or place - **Information:** refers to processed data or a meaningful statement # Methods of Data Processing The following are the three methods that have been widely used for data processing over the years: - The Manual method - The Mechanical method - The Computer method ## The Manual Method The manual method of data processing involves the use of chalk, wall, pen, pencil, and the like. These devices, machines or tools facilitate human efforts in recording, classifying, manipulating, sorting and presenting data. The manual method is: - cumbersome - tiresome - boring - frustrating - time-consuming - susceptible to human errors The manual method does not allow for the processing of large volumes of data on a regular and timely basis ## The Mechanical Method The mechanical method of data processing involves the use of machines such as the typewriter, adding machines and the like. These machines facilitate human efforts in recording, classifying, manipulating, sorting and presenting data or information. The mechanical method is: - routine in nature - noisy - hazardous - error prone - untidy The mechanical method does not allow for the processing of large volumes of data continuously and timely. ## The Computer Method The computer method of carrying out data processing has the following major features: - Data can be steadily and continuously processed - The operations are practically not noisy - There is a store where data and instructions can be stored temporarily and permanently. - Errors can be easily and neatly corrected. - Output reports are usually very neat, decent, and can be produced in various forms such as adding graphs, diagrams and pictures etc. - Accuracy and reliability are highly enhanced ## Characteristics of a Computer - **Speed:** The computer can manipulate large data at incredible speed and response time can be very fast. - **Accuracy:** The accuracy is very high and its consistency can be relied upon. Errors committed in computing are mostly due to human rather than technological weakness. There are in-built error detecting schemes in the computer. - **Storage:** It has both internal and external storage facilities for holding data and instructions. The capacity varies from one machine to the other. Memories are built up in K (Kilo) modules where K=1024 memory locations. - **Automatic:** Once a program is in the computer's memory, it can run automatically each time it is opened. The individual has little or no instruction to give again. - **Reliability:** Being a machine, a computer does not suffer human traits of tiredness and lack of concentration. It will perform the last job with the same speed and accuracy as the first job every time even if ten million jobs are involved. - **Flexibility:** It can perform any type of task once it can be reduced to logical steps. Modern computers can be used to perform a variety of functions like on-line processing, multiprogramming, real-time processing etc. ## The Computing System The computing system is made up of the computer system, the user and the environment in which the computer is operated. ## The Computer System The computer system is made up of the hardware and the software. ## The Hardware The computer hardware comprises the input unit, the processing unit, and the output unit. ### The Input Unit The input unit comprises those media through which data is fed into the computer. Examples include the keyboard, mouse, joystick, trackball and scanner. ### The Processing Unit The processing unit is made up of the Arithmetic and Logic Unit (ALU), the control unit and the main memory. The main memory also known as the primary memory is made up of the Read Only Memory (ROM); is non-volatile memory that permanently stores instructions for your computer, and the Random Access Memory (RAM); is volatile memory that temporarily stores the files you are working on. ### The Output Unit The output unit is made up of those media through which data, instructions for processing the data (program), and the result of the processing operation are displayed for the user to see. Examples of the output unit are the monitor (Visual Display Unit), scanners, speakers and the printer. ## The Software Computer software is the series of instructions that enable the computer to perform a task or group of tasks. A program is made up of a group of instructions to perform a task. Series of programs linked together make up software. Computer programs could be categorized into system software, utility software, and application programs. ## The Computer Users Computer users are the different categories of personnel that operate the computer. We have expert users, casual users, and basic users. ### Expert Users The expert users are users with advanced knowledge about computers software and hardware that require no assistance when working with the computer. They are computer engineers, computer programmers etc. ### Casual Users The casual users are users who have some computer experience and can navigate and use the computer without much assistance. ### Basic Users The basic users are users who just started using the computer and need a lot of assistance. ## The Computing Environment The computing environment includes the building housing the other elements of the computing system namely the computer and the users, the furniture, auxiliary devices such as the voltage stabilizer, the Uninterruptible Power Supply System (UPS), the fans, the air conditioners etc. # A Brief History of Computer Technology A complete history of computing would include a multitude of diverse devices such as the ancient Chinese abacus, the Jacquard loom (1805) and Charles Babbage's "analytical engine" (1834). It would also include a discussion of mechanical, analog and digital computing architectures. As late as the 1960s, mechanical devices, such as the Marchant calculator, still found widespread application in science and engineering. During the early days of electronic computing devices, there was much discussion about the relative merits of analog vs. digital computers. In fact, as late as the 1960s, analog computers were routinely used to solve systems of finite difference equations arising in oil reservoir modeling. In the end, digital computing devices proved to have the power, economics and scalability necessary to deal with large scale computations. Digital computers now dominate the computing world in all areas ranging from the hand calculator to the supercomputer and are pervasive throughout society. Therefore, this brief sketch of the development of scientific computing is limited to the area of digital, electronic computers. The evolution of digital computing is often divided into generations. Each generation is characterized by dramatic improvements over the previous generation in; (i) the technology used to build computers, (ii) the internal organization of computer systems, and (iii) programming languages. ## First Generation Electronic Computers (1937 – 1953) Three machines have been promoted at various times as the first electronic computers. These machines used electronic switches, in the form of vacuum tubes, instead of electromechanical relays. In principle the electronic switches were more reliable, since they would have no moving parts that would wear out, but technology was still new at that time and the tubes were comparable to relays in reliability. Electronic components had one major benefit, however: they could "open" and "close" about 1,000 times faster than mechanical switches. The earliest attempt to build an electronic computer was by J. V. Atanasoff, a professor of physics and mathematics at Iowa State, in 1937. Atanasoff set out to build a machine that would help his graduate students solve systems of partial differential equations. By 1941, he and graduate student Clifford Berry had succeeded in building a machine that could solve 29 simultaneous equations with 29 unknowns. However, the machine was not programmable, and was more of an electronic calculator. A second early electronic machine was Colossus, designed by Alan Turning for the British military in 1943. This machine played an important role in breaking codes used by the German army in World War II. Turning's main contribution to the field of computer science was the idea of the Turning Machine, a mathematical formalism widely used in the study of computable functions. The existence of Colossus was kept secret until long after the war ended, and the credit due to Turning and his colleagues for designing one of the first working electronic computers was slow in coming. The first general purposes programmable electronic computer was the Electronic Numerical Integrator and Computer (ENIAC), built by J. Presper Eckert and John V. Mauchly at the University of Pennysylvania. Work began in 1943, funded by the Army Ordinance Department, which needed a way to compute ballistics during World War II. The machine wasn't completed until 1945, but then it was used extensively for calculations during the design of the hydrogen bomb. ## Second Generation (1954 – 1962) The second generation saw several important developments at all levels of computer system design, from the technology used to build the basic circuits to the programming languages used to write scientific applications. Electronic switches in this era were based on discrete diode and transistor technology with a switching time of approximately 0.3 microseconds. The first machines to be built with this technology include TRADIC at Bell Laboratories in 1954 and TX-0 at MIT's Lincoln Laboratory. Memory technology was based on magnetic cores which could be accessed in random order, as opposed to mercury delay lines, in which data was stored as an acoustic wave that passed sequentially through the medium and could be accessed only when the data moved by the I/O interface. During this second generation many high level programming languages were introduced, including FORTRAN (1956), ALGOL (1958), and COBOL (1959). Important commercial machines of this era include the IBM 704 and 7094. The latter introduced I/O processors for better throughput between I/O devices and main memory. ## Third Generation (1963-1972) The third generation brought huge gains in computational power. Innovations in this era include the use of integrated circuits, or ICs (semiconductor devices with several transistors built into one physical component), semiconductor memories were been used instead of magnetic cores, microprogramming as a technique for efficiently designing complex processors, the coming of age of pipelining and other forms of parallel processing, and the introduction of operating systems and time-sharing. ## Fourth Generation (1972-1984) The next generation of computer systems saw the use of large scale integration (LSI 1000 devices per chip) and very large scale integration (VLSI -100,000 devices per chip) in the construction of computing elements. At this scale entire processors will fit onto a single chip, and for simple systems the entire computer (processor, main memory, and I/O controllers) can fit on one chip. Gate delays dropped to about Ins per gate. Semiconductor memories replaced core memories as the main memory in most systems; until this time the use of semiconductor memory in most systems was limited to registers and cache. Developments in software include very high level languages such as FP (functional programming) and Prolog (programming in logic). These languages tend to use a declarative programming style as opposed to the imperative style of Pascal, C. FORTRAN, et al. ## Fifth Generation (1984 – 1990) The development of the next generation of computer systems is characterised mainly by the acceptance of parallel processing( a method in computing of running two or more processors to handle separate parts of an overall task). Until this time, parallelism was limited to pipelining and vector processing, or at most to a few processors sharing jobs. The fifth generation saw the introduction of machines with hundreds of processors that could all be working on different parts of a single program. The scale of integration in semiconductors continued at an incredible pace, so that by 1990 it was possible to build chips with a million components -- and semiconductor memories became standard on all computers. Other new developments were the widespread use of computer networks and the increasing use of single-user workstations. ## Sixth Generation (1990 to date) Transitions between generations in computer technology are hard to define, especially as they are taking place. Some changes, such as the switch from vacuum tubes to transistors, are immediately apparent as fundamental changes, but others are clear only in retrospect. Many of the developments in computer systems since 1990 reflect gradual improvements over established systems, and thus it is hard to claim they represent a transition to a new "generation”, but other developments will prove to be significant changes. One of the most dramatic changes in the sixth generation is the explosive growth of wide area networking. Network bandwidth has expanded tremendously in the last few years and will continue to improve for the next several years. # Classification of Computers Although there are no industry standards, computers are generally classified in the following ways: - Classification Based on Signal Type - Classification by Purpose - Classification of Computers According to Capacity ## (a) Classification Based on Signal Type There are basically three types of electronic computers. These are the Digital, Analog and Hybrid computers. ### The Digital Computer This represents its variables in the form of digits. The data it deals with, either numbers, letters or other symbols, are converted into binary form on input to the computer. The data undergoes a processing after which the binary digits are converted back to alpha numeric form for output for human use. Because of the fact that business applications like inventory control, invoicing and payroll deal with discrete values (separate, disunited, discontinuous), they are best processed with digital computers. As a result of this, digital computers are mostly used in commercial and business places today. ### The Analog Computer An analog computer represents quantities by physical analogies. It represents physical quantities, such as distance, velocity, acceleration, temperature, pressure, or angular position, forces or voltages in mechanically or electrically equivalent circuits. That is, it functions by setting up physical models corresponding to mathematical functions. It measures rather than counts. This type of computer sets up a model of a system. The common type represents its variables in terms of voltage and sets up circuit analog to the equation connecting the variables. The answer can be either by using a voltmeter to read the value of the variable required, or by feeding the voltage into a plotting device. Analog computers hold data in the form of physical variables rather than numerical quantities. In theory, analog computers give an exact answer because the answer has not been approximated to the nearest digit. Whereas, when we try to obtain the answers using a digital voltmeter, we often find that the accuracy is less than that which could have been obtained from an analog computer. There are two useful properties of this computer once it is programmed: - It is simple to change the value of a constant or coefficient and study the effect of such changes. - It is possible to link certain variables to a time pulse to study changes with time as a variable, and chart the result on an X-Y plotter. ### The Hybrid Computer In some cases, the computer user may wish to obtain the output from an analog computer as processed by a digital computer or vice versa. To achieve this, he set up a hybrid machine where the two are connected and the analog computer may be regarded as a peripheral of the digital computer. In such a situation, a hybrid system attempts to gain the advantage of both the digital and the analog elements in the same machine. This kind of machine is usually a special-purpose device which is built for a specific task. It needs a conversion element which accepts analog inputs, and outputs digital values. Such converters are called digitizers. There is a need for a converter from analog to digital also. It has the advantage of giving real-time response on a continuous basis. Complex calculations can be dealt with by the digital elements, thereby requiring a large memory, and giving accurate results after programming. They are mainly used in aerospace and process control applications. ## (b) Classification by Purpose Depending on their flexibility in operation, computers are classified as either special purpose or general purpose. ### Special-Purpose Computers A special purpose computer is one that is designed to solve a specific class of problems. Such computers may even be designed and built to handle only one job. In such machines, the steps or operations that the computer follows may be built into the hardware. Most of the computers used for military purposes fall into this class. Other examples of special purpose computers include: - Computers designed specifically to solve navigational problems. - Computers designed for tracking airplanes or missiles. - Computers used for process control applications in industries such as oil refinery, chemical manufacture, steel processing and power generation. - Computers used as robots in factories like vehicle assembly plants and glass industries. ### General Attributes of Special-Purpose Computers - Special-purpose computers are usually very efficient for the tasks for which they are specially designed. - They are very much less complex than the general-purpose computers. - The simplicity of the circuiting stems from the fact that provision is made only for limited facilities. - They are very much cheaper than the general-purpose type since they involve fewer components and are less complex. ### General-Purpose Computers General-purpose computers are computers designed to handle a wide range of problems. Theoretically, a general-purpose computer can be adequate by means of some easily alterable instructions to handle any problems that can be solved by computation. In practice, however, there are limitations imposed by memory size, speed and the type of input/output devices. Examples of areas where general purpose computers are employed include the following: - Payroll - Banking - Billing - Sales analysis - Cost accounting - Manufacturing scheduling - Inventory control ### General Attributes of General-Purpose Computers - General-purpose computers are more flexible than special purpose computers. Thus, the former can handle a wide spectrum of problems. - They are less efficient than the special-purpose computers due to such problems as the following: - They have inadequate storage - They have low operating speed - Coordination of the various tasks and subsections may take time - General-purpose computers are more complex than special purpose computers. ## (c) Classification of Computers According to Capacity In the past, the capacity of computers was measured in terms of physical size. Today, however, physical size is not a good measure of capacity because modern technology has made it possible to achieve compactness. A better measure of capacity today is the volume of work that a computer can handle. The volume of work that a given computer handles is closely tied to the cost and to the memory size of the computer. Therefore, most authorities today accept rental price as the standard for ranking computers. Here, both memory size and cost shall be used to rank (classify) computers into three main categories as follows: - Microcomputers/personal computers - Medium/mini/small computers - Large computer/mainframes. ### Microcomputers Microcomputers are the cheapest class of computers. In the microcomputer, we do not have a Central Processing Unit (CPU) as we have in the larger computers. Rather we have a microprocessor chip as the main data processing unit. They are the cheapest and smallest, and can operate under normal office conditions. Examples are IBM, APPLE, COMPAQ, Hewlett Packard (HP), Dell and Toshiba, etc. ### Different Types of Personal Computers (Microcomputers) Normally, personal computers are placed on the desk; hence they are referred to as desktop personal computers. Still other types are available under the categories of personal computers. They are: - **Laptop Computers:** These are small size types that are battery operated. The screen is used to cover the system while the keyboard is installed flat on the system unit. They could be carried about like a box when closed after operation and can be operated in vehicles while on a journey. - **Notebook Computers:** These are like laptop computers but smaller in size. Though small, the notebook computer comprises all the components of a full system. - **Palmtop Computers:** The palmtop computer is far smaller in size. All the components are complete as in any of the above, but it is made smaller so that it can be held on the palm. ### Uses of the Personal Computer (Microcomputers) A personal computer can perform the following functions: - It can be used to produce documents like memos, reports, lecture notes, letters and briefs. - It can be used to calculate budgets and accounting tasks - It can analyse numeric functions - It can create illustrations - It can be used for electronic mails - It can help in making schedules and planning projects - It can assist in searching for specific information from lists or from reports. ### Advantages of the Personal Computer (Microcomputers) - The personal computer is versatile: it can be used in any establishment - It has faster speed for processing data - It can deal with several data at a time - It can attend to several users at the same time, thereby being able to process several jobs at a tine - It is capable of storing several data - Operating the personal computer gives less fatigue - It is possible to network personal computers, that is, linking of two or more computers. ### Disadvantages of the Personal Computer (Microcomputers) - The personal computer is costly to maintain - It is very fragile and complex to handle - It requires special skill to operate - With inventions and innovations every day, the personal computer is at the risk of becoming obsolete - It can lead to unemployment, especially in less developed countries - Some computers cannot function properly without the aid of a cooling system, e.g, air conditioners or fans in some locations. ### Mini Computers Mini computers have memory capacity in the range '128-256 Kbytes' and are also not expensive but reliable and smaller in size compare to mainframe. They were first introduced in 1965; when DEC (Digital Equipment Corporation) built the PDP. ### Mainframe Computers The mainframe computers, often called number crunchers have memory capacity of the order of '4 Kbytes', and are very expensive. They can execute up to 100 MIPS (Meanwhile Instructions per Second). They have large systems and are used by many people for a variety of purposes.