December 16, 2022

Introduction Physiology refers to the branch of biology that deals with the study of functions and activities of life or of living matter such as organs, tissues or cells. It aims at understanding the mechanism of living. In simpler terms, physiology refers to the processes and functions that take place inside the body cells of organisms. Cell physiology refers to the study of functions of the cell structures. The cell structures perform various functions of life. In particular: Chloroplasts play a vital role in carbohydrate synthesis. Mitochondrion produces energy required to carry out life processes. Ribosomes manufacture of proteins. These physiological processes require various raw materials for them to take place. For photosynthesis to occur, carbon (IV) oxide, mineral salts and water have to be taken into the chloroplasts. For respiration (energy production) to take place, food substrate such as glucose and oxygen have to be taken into the mitochondrion. Energy, carbon (IV) oxide, water and alcohol (in plants) are some of the end products of respiration. Some of the end products of the physiological processes such as carbon (IV) oxide can be harmful when allowed to accumulate in the cells. They, thus, have to be eliminated from the cells. This implies that there is a constant flow of materials in and out of the cells and the cell organelles where these physiological processes are taking place. There is a constant movement of materials across the cell membrane in the cells. This chapter discusses the properties of the cell membrane and the processes through which materials move in and out of the cells. Structure of the membrane A membrane is a surface structure that encloses the cell and cell organelles. The membranes include the cell membrane, tonoplasts, nuclei membrane, mitochondrial membrane and chloroplast membrane. The membranes have a common basic structure which regulates the movement of materials in and out of the cells. The cell membrane is made up of a phospholipid layer sandwiched by two protein layer (it is a lipoprotein layer) the overall thickness of the cell membrane is about 7.5 nm thick. The membrane is perforated by small pores that allow the passage of substances in and out of the cells. Properties of the cell membrane The cell membrane is semi permeable– The pores that occur on the cell membrane allows the passage of the small size molecules but does not allow the passage of the large sized molecules. Such a membrane is said to be selectively permeable or semi-permeable. In particular, when a cell is surrounded by a dilute sugar solution, the small sized water molecules will enter the cell but the larger sugar molecules will not pass through the cell membrane. In contrast, the cell wall is permeable as it allows both sugar and water molecules to pass through it; it has larger pores. This property of selectively permeability enables the cell membrane to select what enters and leaves the cell. The cell membrane is sensitive to changes in temperature and pH– Cell membranes are made up of protein. Proteins are adversely affected by extreme changes in temperature and pH. Changes in temperature and pH will alter the structure of the cell membrane thereby hindering the normal functioning of the cell membrane. High temperature denatures (destroys) the proteins thereby impairing the functions of the cell membrane. The cell membrane possesses electric charges– The cell membrane has both positive and negative charges. These charges affect the manner in which substances move in and out of the ells. The charges also enable the cell to detect changes in the environment. Physiological Processes of the Cell membrane In this section, we discuss the various physiological processes through which materials move in and out of the cells across the cell membrane. Materials move in and out of the cells through three main physiological processes: Diffusion Osmosis Active transport Diffusion From kinetic theory, matter is made up of particles that are in continuous random motion. In solids, the particles are at fixed positions and can only vibrate at these fixed positions. In liquids and gases, the particles are loosely held and are free to move from one region to another randomly. This movement of gas or liquid particles is observed to be from regions of high concentration to a region of low concentration. The process by which particles move from a region of high concentration to a region of low concentration is known as diffusion. In particular, the scent of a flower or perfume experienced by an individual is as a result of the flower scent particles or perfume particles move from a region of high concentration. Diffusion occurs until the regions have an even concentration of the liquid or gas particles. The difference in concentration of particles between the region of high concentration and region of low concentration is known as the diffusion gradient/concentration gradient. Demonstration of the process of diffusion using potassium manganate (VII) Requirements: potassium manganate (VII) crystals, glass tubing, 100 cm3 beaker and water. Procedure Hold the glass tubing vertically in a beaker so that one end of the tubing rests on the bottom of the beaker. Cautiously and quickly drop a crystal of potassium manganate (VII) through the upper opening of the glass tubing. Close the upper hand of the glass tubing with the thumb. Half fill the beaker with water. Carefully withdraw vertically the glass tubing so that the crystal is left undisturbed at the bottom of the beaker. Record your observations for the first 15 minutes. Explain your observations. Expected observations After some time, the purple colour of the potassium manganate (VII) spread throughout the water and eventually all the water turned purple. Explanation The crystals of potassium manganate (VII) are highly concentrated with the potassium manganate (VII) particles. The potassium manganate (VII) particles break away from the crystals, dissolve in water and then diffuse through the water until they are evenly distributed. The Role of Diffusion in Living Organisms In Plants Diffusion plays an important role in plants in that: It

Introduction The bodies of living organisms are made up of small microscopic units called cells. The cells make up the structures of the living organisms and are responsible for carrying out various biological processes in the bodies of the living organisms. Some organisms are made up of a single cell only e.g. amoeba and other bacteria in the kingdom monera. These organisms are known as unicellular organisms. Other organisms are composed of many cells and are said to be multicellular. Most plants and animals are multicellular. A cell is the basic functional unit of an organism. Being very small, the cell cannot be seen with a naked eye. A powerful magnifying instrument is required. The microscope is used to view the cells. Development of the light microscope In 1650, Zacharias Jansen invented the compound microscope which combines two lenses for greater magnification. In 1665, Robert Hooke used an improved compound microscope to observe cells. Between 1650 and 1700, Anthony Van Leewenhoeck developed a better microscope with lenses which provided a greater magnification. He used the microscope to view nuclei and unicellular organisms including bacteria. The development of the electron microscope in 1930s significantly improved microbial studies. Through this microscope, it was possible to study very finer details of structures. The Light Microscope This is the most commonly used microscope in schools and institutions that do not focus on very fine details of the internal structures of cells. The light microscope uses a beam of light to illuminate the specimen being studied. A microscope is a delicate and expensive instrument that should be handled with care. It is imperative to understand the parts and functions of various parts of a microscope. In a light microscope, the eye piece and the objective lenses both contribute to the magnification of the specimen. The total magnification of the specimen viewed under a light microscope will be given by: Magnification= Eyepiece lens magnification X Objective lens magnification In particular, if the eyepiece lens magnification is X10 and objective lens magnification power is X8, then the total magnification of the specimen would be: Magnification=Eyepiece magnification X Objective lens magnification = 10 X8 =X80. The following rules should be observed when handling the microscope: Always use both hands when carrying the microscope. One hand should hold the base to provide support while the other hand holds the limb. Never place the microscope too close to the edge of the working bench or table. Do not touch the mirror or the lenses with your fingers. Dirty lenses should be cleaned using a special soft lens tissue paper or tissue paper moistened with ethanol. The other parts of the microscope may be cleaned using a microscope. Do not wet any part of the microscope. Make sure the low power objective lens clicks into position in line with the eye piece before and after use. After use, always clean and store the microscope in a safe place, free from moisture and dust. How to use the Microscope Place the microscope on the bench with the stage facing away from you. Turn the low power objective lens until it clicks into position. Ensure that the diaphragm is fully open. Look through the eye-piece with one eye; meanwhile adjust the mirror under the stage to ensure that maximum light can pass through. The circular area seen is referred to as the field of view. Again look through the eyepiece while adjusting the mirror under the stage to ensure that sufficient light is passing through the specimen. Use the coarse adjustment knob to bring the low power objective lens to the lowest point. Viewing through the eye-piece, turn the coarse adjustment knob gently until the specimen comes into focus. Use the fine adjustment knob to bring the image into sharp focus. Make a drawing of what you observe. For higher magnifications, turn the medium power objective lens into position and adjust the focus using the coarse adjustment knob. For sharper images, use the fine adjustment knob. If finer details are required, turn the high power objective lens into position; now use only the fine adjustment knob to bring the details into sharper focus. Cell Structures as seen under the Light Microscope The structures within the cell are referred to as organelles. Some of the cell organelles that can be observed under the light microscope include the cell wall, cell membrane, cytoplasm, nucleus, vacuole and chloroplasts. These cell organelles perform specific functions within the cell. The cell as seen under the Electron Microscope The electron microscope is more powerful than the light microscope. It uses a beam of electrons to illuminate the specimen instead of light as in the case of light microscope. Electron microscope can magnify an object up to 500, 000 times. It also has a very high resolving power. Resolving power is the ability to distinguish between separate things which are close to each other. The high resolving power makes the electron microscope a very important research tool in microbiology. Through the electron microscope, very fine details of the cell can be observed. Structure and Functions of the Cell Organelles Cell membrane The cell membrane, also known as plasma membrane or plasmalemma consists of three layers when viewed under the electron microscope. The three layers are composed of one layer of phospholipid sandwiched between two protein layers. It is flexible and has pores. The cell membrane is important in that: It encloses the cell contents. It allows for selective movement of materials in and out of the cells. The pores allow materials particularly of small molecular size to move in and out of the cells. 2. Cytoplasm Cytoplasm consists of a fluid medium in which chemical reactions take place. It contains organelles and other inclusions such as starch, glycogen, fat droplets and many other dissolved substances. Cytoplasm is not static; it undergoes a movement known as cytoplasmic streaming. It provides a suitable medium for cellular reactions to take place. 3. Mitochondrion Mitochondrion is a sausage shaped organelle that provides sites

Introduction Biology has been defined as the study of living things (living organisms). Even though all living things share similar characteristics discussed in the introductory chapter, the living things exhibit a lot of differences. In particular, animals and plants are all living things yet they differ in many aspects. Amongst animals and plants also there exist a lot of differences. There are millions of different plant and animal types exhibiting a range of differences. This created a need for a classification system of living things to make study of the living organisms easier. Classification refers to the grouping of living organisms according to their structure. In classification, organisms that share a lot of similarities are placed under one group referred to as a taxon (plural= taxa). Other than the similarities, grouping of the organisms also takes into account the evolutionary relationships (phylogeny) of the organisms. It is believed that all organisms once had a common ancestor (theory of evolution). During classification, organisms that are believed to have evolved along the same line of evolution are placed in one taxon. The scientific study of classification is known as taxonomy. A biologist studying taxonomy is a taxonomist. In classifying organisms taxonomists to a great extent rely on the use of external observable features of organisms. External features of plants used in classification The rhizoids as in moss plant Fronds in ferns The type of root; tap root, adventitious, fibrous, prop, buttress roots. Stem presence and type. Presence or absence of flowers Type of leaves; simple or compound; leaf venation- parallel or net work veined. Presence and types of fruits and cones. External features of animals used in classification Tentacles in hydra Body covering- feathers, scales, hair or fur Shells in snails Wings in birds Proglotids in tapeworms Mammary glands in mammals Locomotory structures Body pigmentation Importance of Classification Classification systems improve our ability to explain relationships among things. Classification helps in identifying living organisms into their correct groups for reference. Classification helps in avoiding chaos and confusion when dealing with animals as it arranges the information on organisms in an orderly manner. Classification brings together living organisms with similar characteristics together but separate those with different features. Taxonomic systems provide relatively stable, unique, and unequivocal names for organisms It makes the study of such a wide variety of organisms easy. It projects before us a good picture of all life forms at a glance. It helps us understand the interrelationship among different groups of organisms. It serves as a base for the development of other biological sciences such as biogeography etc. Various fields of applied biology such as agriculture, public health and environmental biology depend on classification of pests, disease vectors, pathogens and components of an ecosystem. Historical background of Classification In the past, scientists used to classify organisms based on personal conveniences. They heavily relied on very few observable features. There was no standard classification system as each and every scientist would classify organisms in a way that would suit his intentions. In particular, living organisms were simply classified as plants or animals. The plants were also classified as herbs, trees, shrubs. Animals were also grouped into herbivores, carnivores and omnivores. Some biologists would also classify plants as: Edible or non edible Flowering or non-flowering The modern classification systems take into account the evolutionary relationships between living organisms. It has overcome the many weaknesses of the artificial (traditional) classification systems. From the original parents, arose new groups of organisms that went under structural changes that enabled them to live in different habitats. The structural changes account for the great diversity of living organisms observed today. Carolus Linnaeus, a Sweddish biologist is largely credited for his significant contribution to the development of the modern classification system. Taxonomic Units of Classification Taxonomic units of classification refer to the groups or taxa into which organisms are placed as a matter of convenience. Grouping of organisms in these groups is based on easily observable characteristics that are common in that group. Living organisms which share a lot of characteristics are placed in the same group. Each taxonomic unit reflects the position of an organism in relation to the others in the classification scheme. In a classification scheme, a hierarchy of groups is recognized and it proceeds from the first largest and highest group, the kingdom to the smallest and lowest unit, the species. There are seven taxonomic units of classification. All living organisms are classified into five major kingdoms: Kingdom Monera– This is composed of microscopic unicellular organisms mainly bacteria e.g amoeba. Kingdom Protoctista– This kingdom is comprised of members who are microscopic. Though, some are large enough to be seen with the naked eyes. Members of this kingdom include algae and protozoa. Kingdom Fungi– Members of this kingdom comprises the mushrooms, toadstools, moulds and yeast. Kingdom Plantae– This kingdom comprises the moss plant, ferns, maize plants, hibiscus, meru oak tree etc. Kingdom Animalia – Members of this kingdom include the tapeworms, hydra, fishes, human beings, lizards, earthworms etc. In hierarchy of classification, a kingdom is further divided into several phyla (plural of phylum) or divisions (in plants). Within the phyla or divisions, organisms are further sorted out into groups known as classes based on their similarities and mode of life. Each class is further subdivided into small groups called orders based on structural similarities. Orders subdivide into families which subdivide into genera (plural for genus).Genera are then subdivided into smaller units of classification called the species. Species is the smallest unit of classification whose members share many similarities and can freely interbreed to give rise to fertile or viable offsprings. Members of a particular species can, however, exhibit various differences e.g. differences in skin colour or body forms. Within the species, organisms can further be classified based on the differences in colour or forms. In humans, this gives the races, in animals the term used is breed while in plants, variety is preferred. In bacteria, the term strain is used to describe the

Biology is a branch of science that deals with the study of living things. There are diverse forms of life on earth ranging from the invisible microscopic living things to the gigantic life forms. It aims at explaining the living world in terms of scientific principles. It is important to note, however, that living things interact with the non living things in the environment as well. Biology, therefore also entails the study of non living things as well. The role of human beings in shaping the environment is also investigated in biology. In summary, biology deals with the study of origins, types, nature, growth, development, interactions and maintenance of all life forms on earth. Branches of Biology Biology is such a broad field of knowledge. It is divided into two broad branches Zoology– This is a branch of biology that deals with the study of animal life. Botany- This is a branch of biology that deals with the study of plant life. Within the two branches, there exist even smaller branches because the branches (botany and zoology) are very wide and complex. The smaller branches of biology include: Ecology– This is the study of the interrelationships between organisms and their environment. Ecology aims at establishing how organisms are related to each other and their environment. Ecology is further subdivided into smaller branches. These can be forest ecology, marine ecology, rangeland ecology etc. Genetics- This sub-branch of biology deals with the study of inheritance and variation. It deals with the study of how variations (differences) occur between parents and their offspring. It is also concerned with how various characteristics are passed on from parents to offspring. Entomology– This is the study of insects. Parasitology– This is the study of parasites. Physiology– This deals with the study of the functions of various structures of an organism. It deals with the processes that take place in the body of organisms. Anatomy– The study of the internal structure of organisms Microbiology– This is the study of microorganisms Bacteriology– The study of bacteria Ornithology– This is the study of birds Itchthology-This is the study of fishes This list is in-exhaustive as there are very many other branches of biology. Importance of biology The study of biology is very important. The knowledge acquired from this study can benefit an individual in myriad ways. The study of biology is important in that: The knowledge acquired from the study of biology can be very helpful in solving environmental problems such as food shortage, poor health services, pollution and environmental degradation. The study of biology can grant one an entry into various careers such as medicine, veterinary medicine, animal husbandry, horticulture and dentistry. The study of biology leads to development of scientific skills which are very useful in life. These include skills of observing, identifying, recording, classifying, measuring, analyzing and evaluating. These skills can enable one learn how to make right choices and lead an improved life. Through the study of biology man learns the causes of human, plant and human diseases and how best these diseases can be prevented and cured. Biological knowledge acquired in the study of biology is very useful in enhancing international cooperation. Some biology related international conventions include: Joint development of HIV/AIDS vaccine by Kenyan and British scientists. The coordinated fight against Severe Acute Respiratory Syndrome involving scientist all over the world. The fight to save the ozone layer from depletion through various international agreements such as the Kyoto protocol. Management of resources through international treaties such as the CITES (Convention against International Trade on Endangered Species). CHARACTERISTICS OF LIVING THINGS Living things share a lot of characteristics in common. These characteristics are discussed below. Nutrition Nutrition is the process by which living things obtain and assimilate (utilize) nutrients. Living things require nutrients for various purposes; growth, repair of worn out tissues and for provision of energy. Plants manufacture their own food using light energy, carbon (IV) oxide, water and mineral salts through the process of photosynthesis. Conversely, animals feed on already manufactured foods from plants and other animals. 2. Respiration Respiration is the process by which food substances are chemically broken down to release energy. During respiration, oxygen is used while energy, carbon (IV) oxide and water are released. Respiration occurs in all living cells. The energy produced in living things is very useful as it enables the living things carry out some of their physiological processes.  The energy is also required for growth and development, movement and repair of worn out tissues. 3. Gaseous Exchange Gaseous exchange refers to the process by which living things exchange oxygen and carbon (IV) oxide across the respiratory surfaces. Animals always take in air rich in oxygen and give out air rich in carbon (IV) oxide. Carbon (IV) oxide is a waste product of chemical reactions in the body. Animals require oxygen for respiration. Gaseous exchange, therefore, enables animals obtain oxygen for respiration and get rid of carbon (IV) oxide, a waste product. Plants, however, require carbon (IV) oxide for photosynthesis during the day. They give away oxygen as a by-product. The plants equally require oxygen for respiration and give away carbon (IV) oxide. 4. Excretion This is the process by which living things separate and eliminate the waste or harmful materials resulting from chemical reactions within the cells. These harmful waste products of metabolism maybe toxic to the body if they are left to accumulate in the cells of the living things 5. Growth and Development Growth refers to an irreversible increase in size and mass while development refers to the irreversible change in complexity of the structure of living things. Growth and development of living things is essential as it enables the living things to attain maximum size that can enable them to perform their functions and roles. 6. Reproduction This is the process by which living things give rise to new individuals of the same kind. All living things reproduce. Reproduction is essential as it leads to perpetuation of species and it

TOPIC 1 : INTRODUCTION TO BIOLOGY – Click to view TOPIC 2 : CLASSIFICATION I – Click to view TOPIC 3 : THE CELL – Click to view TOPIC 4 : CELL PHYSIOLOGY – Click to view TOPIC 5 : NUTRITION IN PLANTS AND ANIMALS – Click to view

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4.1                   DEFINITION OF THE TERM: ‘OPERATING SYSTEM’  Operating System as defined earlier, is a set of programs available within  the  system  software  that  standardizes  the  way  a  computer’s resources are made available to the user and to applications software.   4.2                   FUNCTIONS OF AN OPERATING SYSTEM The following functions are identified as common to all Operating Systems: 4.2.1          Memory Management An Operating System allocates memory to itself and to its resident system  programs,  sets  aside  areas  of  application  programs  and  user partitions, arranges the input and output buffers (areas on RAM where input data and output data are temporarily stored) and reserves storage for specialized purposes. 4.2.2          Input/Output (I/O) Management The Operating System controls reading of data coming in from the various input devices into the memory and writing of data to output devices such as printers. The Operating System will ensure that each time the user types in commands those inputs are accepted into the memory, and if the latter is busy the it holds the same temporarily on buffers until the memory is free and also does the same to output data awaiting to be displayed on the monitor or to be sent to the printer if the same are busy. 4.2.3          Resource Allocation Operating System load programs into the computer memory and starts  them  running  after  receiving  instructions  from  the  user,  at  the same time, operating systems must have ability to divide resources available  to  different  users,  memory  and  of  course  the  peripherals  to different processors going on at the same time so that none of the users gets “stuck” or “deadlocked” during the operation for lack of a computer resource. 4.2.4          Error Handling Any Operating System must have the ability to handle errors in the computer system be it hardware or software faults and be able to provide routines to correct these errors. 4.2.5          Provision for User Interface Any Operating System should have the ability to receive commands from the user and respond to them accordingly. 4.2.6          Interrupt Handling An interruption could be caused by software errors, mechanical faults of a machine or by the operator by pressing the Break key for example which halts the system. The operating system should always be able to handle such interrupts without causing any malfunctions as a result.   4.3        TYPES OF OPERATING SYSTEMS  There are majorly two types of Operating Systems that we will discuss in this section. 4.3.1          Single User System In this type of Operating System, only one user can use the machine at a time, load one program at a time in the main memory and process only that one program. Most of the small microcomputers employ single user systems. Examples are Ms-DOS, Pc-DOS and Windows. 4.3.2          Multi User System This system as the name suggests is for multi user, as opposed to the single user system. This system is employed by larger microcomputers and minicomputers. More than one program can be loaded into the main memory by different users and processed at the same time in an interactive manner. Examples of such an operating system are UNIX and Windows NT.   4.4             FILE MANAGEMENT  Medium of storage employed by most microcomputers is often disk. Data that is stored on disks are often held in a file. The latter is often referred to as a group of related records. The records may hold data about customers, employees of the organization and names of students in a school and the like depending on the organizations. Therefore, the file as a group of program instructions is actually a computer program. When files are stored on such storage media, then the term “file” refers to anything stored on the medium, be it a program or data file. 4.4.1          File and Directories The work of the Operating System is to keep or maintain a directory of the address of the files on disk. Each file on the storage media is assigned a name called filename (one word). The directory is a list of filenames and the disk addresses at which the file may be found. When the user refers to a particular filename, it causes the operating system to consult its directory of filenames, locate the address of the required file and make it ready for use. Let us have a look at a directory listing of files of a system disk using Ms DOS. All of the files in this directory are programs. A system disk is so called because it contains the directory system. We shall list directory for system drive A: Volume in drive A: has no label. Directory of A: COMMAND     COM   18107 13-12-97                 13.00PM SYS COM740713-12-97 13.00PM DIRECTORY                    COM 1307 13-12-9713.00PM FINDEXE 127813-12-97 13.00PM 4 FILE(S) 142890 BYTES FREE What the list shows: the name of the file g. COMMAND Filename extension e.g. COM The number of bytes contained in this file Date and time on which it was printed into the The total figure at the bottom of this directory listing show the number of bytes remaining for storing other MS-DOS has certain rules for formation of filenames for example; A filename must not exceed 8 characters in length and in some cases requires filename extensions, which is 3- character in addition to the filename. In the above example, COM and EXE are extensions. Although not visible, there is usually a full stop between the filename and the extension e.g. Diskcopy.COM is the complete name for the above file. The user has to type in the computer name of the file including the period in order to effectively use some file maintenance utilities like copying or deleting. Filename extensions usually indicate the type of file for example “COM” and “EXE” above will refe-7r5-to program files. 4.4.2          Directory Hierarchy Files stored on a disk can always be organized into subdirectories. Directory hierarchy refers to a “tree” like structure formed by directory – subdirectories – files. For example, we could have a directory called KENYA with

3.1       BEHAVIOUR IN THE COMPUTER LAB  Computer lab forms a very important section of an organization or school and therefore strict rules in terms of behaviour of personnel/students working/studying in the lab needs to be put in place and adhered to. One factor to be taken into consideration is the cost involved in setting up the lab including the cost of equipment. This should not be taken for granted and computers and other peripherals damaged in the short run could result in great losses to the organization. Cleanliness is a factor that stands out in the lab. The personnel need to be clean while in the lab. Dust in the hands, oil on fingers is not allowed among personnel/students. Foodstuffs to the lab is not allowed as the broken pieces from such will ultimately find their way into the peripherals e.g keyboards, disk drive and so on. Depending on what material cover is on the floor, certain shoes tend to cause a lot of distraction by making noise to the rest of the seated personnel. This slows down the work process as attention will definitely be shifted. External disks into the lab are not recommended as this may result in virus infection to the system in the lab from outside sources. Internal disks should not be allowed to leave the room. Some stringent procedures should be laid down to check the personnel who ignore  the  rule.  If  this  is  not  observed,  it  may  lead  to  data  from  the organization being exposed to rivals or would be “hackers” – those who gain access to the system without authority. Any mechanical or technical faults noted should always be reported to the technical personnel immediately for attention. Non-technical personnel should never attempt to deal with such a fault! It is important also that every personnel make routine backup copies of every work done in the lab as this will save the organization from any data loss in the event of disaster. Shutting down and booting of computers is very important. Strict procedures depending on the operating system specification should be adhered to, otherwise damages to the disk in the long run and fragmentation of files and storage in the storage location will happen. This will cause delays in reading and writing to the same. All equipment should not be moved around the lab rather they should always be used where they are installed! Changing of peripherals from one machine to another is not an encouraged practice. Let a mouse meant for machine A remain the machine; if it does not work, please ask a technical personnel to attend to it, but do not interchange it with another!   3.2                   HANDLING OF MATERIALS AND EQUIPMENT Handling of some materials and equipments in the lab should be a privilege. In other words, some disks and special machines like a server (in the case of a network) should not be for everyone, only those authorized should be allowed for example to keep installation disks and so on. Generally the computers and peripherals in the laboratory should always be handled with care since all of them have soldered electronic parts within them that when poorly handled and perhaps dropped then such parts will always either break or be dislocated. This will mean the equipment is damaged. It is recommended that every movement to machines in the lab be done using a trolley. No equipment should ever leave the lab unless with direct authority from the right person. Computer cables should, if detached, be properly returned each to the right machine. Technical operations in the lab should be left for only technical personnel. If every Tom, Dick and Harry in the lab assume to repair every damaged equipment, then more will be worse off than they were. Disks should be kept from natural hazards like excessive temperatures,  water and dust  places  and a way from  magnets  if  data integrity is to be maintained.   3.3                   FIRE AND ACCIDENTS  Fire and other accidents in the lab are possibilities. Such accidents would include electrocution of an employee/student, slipping and falling on a slippery floor. Fire is a big threat to data loss and equipment. Every lab should always offer training of how to handle fir in thee event of such calamity and of course fir-fighting equipment like fire extinguishers for example hand held CO2 and BCF extinguishers should always be available. Data should also always be kept in fireproof safes to avoid loss of data loss in such event. Insuring of equipment and software in the organization with insurance firms will help since after such an accident, the firm is paid.   3.4                   CHEMICALS AND COMBUSTIBLE MATERIAL Chemicals and combustible materials should always be located on special places. False floors and ceilings should always be available for chemicals like fluorocarbon fluid used as a cooling agent for mainframe. Such pipes and ducts should pass either up on false ceilings or below false floors. Combustible materials like fire extinguishers should be located in places visible to everyone but with strict instructions to be touched only in the event of a fire break out. Other materials that could be harmful to the environment should be transmitted through properly located ducts.   3.5                   VENTILATION IN THE COMPUTER LAB/WORKING AREA  Windows provide adequate ventilation in labs. Such windows must not be very wide as such will always be vulnerable to entry by intruders. Any ventilation apart from the window should always be higher up and very small in size. Every ventilation again, mostly windows, should have a well-dropped curtain so as to keep private the operations in the lab.   3.6                   SAFETY PRECAUTIONS AND PRACTICES  Cabling Cables in the lab should be properly located either on false floor or ceiling or along the walls so as to avoid interference for example with communication coolers in the lab. Cables put haphazardly may result in possible power disconnection if stepped on or pushed around. 3.6.2          Stable Power Supply Provision for stable, adequate and

DIAGRAMMATIC REPRESENTATION OF DIVISIONS OF A COMPUTER The following diagram shows the basic physical computer breakdown that will serve as a reference throughout the chapter. KEY: C.P.U      –      Central Processing Unit A.L.U      –      Arithmetic Logic Unit DOS –              Disk Operating System ROM- Read Only Memory RAM- Random Access Memory DBMS- Data Base Management System   2.1          DISTINCTION BETWEEN HARDWARE AND SOFTWARE  A Computer hardware from the simplest point of view is the physical or tangible parts of a computer whereas software are the intangible parts that help the computer to do its task. From a technical stand point, the following are the valid definitions and hence the distinction between the two terms. A  hardware  is  a  name  that  describes  all  the  electronic,  electrical  and mechanical components of a computer together with its peripheral devices. A software is the name that describes all the programs that are used to run the computer or do a specific task together with its documentation. Explanation of the terms Peripheral devices referred to above are: input devices e.g keyboard, mouse or output devices e.g monitor, printer. These are devices that are used at the periphery or at the side or alongside the computer. Documentation refers to, in its simplest form, the manual that helps the user to know how the different parts of the software work, how to install it, uninstall, trouble shoot or as a reference book. The definition of software is not complete until documentation is included.   2.2          THE COMPLETE COMPUTER SYSTEM Because of the recent advances in hardware technology, people have thought of computers as hardware devices only. This is far from the truth. The fact is, the hardware is only one part of the complete system. Without programs to tell the computer what to do, they remain immobile and unproductive, just like an automobile without fuel. A computer system is therefore defined as a combination of hardware devices and programs assembled to accomplish specific tasks. The  broad  categories  of  programs  are  often  employed  by  computer’s operation. One category of program is known as Operating system. As the name suggests, the operating system controls the basic aspects of the computer’s operation. It is the driver of the computer. The other category consists of the Application program which instructs the computer to perform those procedures necessary to get some jobs done;  for example Word-processing, Accounting programs; as a group are often called Software. Therefore, the three components of a complete  computer  system  are:  Hardware,  the  Operating  System  and Application Software. The following diagram (fig. 2.3) shows the relationship between these three components. 2.4         ELEMENTS OF A COMPUTER HARDWARE SYSTEM  The hardware components of a computer system consist of a set of interconnected electronic and mechanical devices. All computing machines be it a calculator, a microcomputer or a mainframe has the same parts. The  parts  of  a  hardware  system  are:  Input  devices  e.g  Keyboard, Output devices e.g Monitor, Printer and the Central Processing Unit which comprises of Control Unit (CU) and the Arithmetic Logic Unit (ALU) and Memory. The figure 2.5 shows the parts of a computer hardware system 2.5          Functional Organization of the Elements of a Computer System   Fig. 2.6 below shows the major physical components of a computer system 2.6         DESCRIPTION OF THE CENTRAL PROCESSING UNIT  The Central Processing Unit is the main component of a computer hardware system. It is usually referred to as the CPU. It consists of three parts. The main part of the CPU is the memory or primary storage, where data being processed and the programs controlling the computer are contained. Arithmetic Logic Unit forms the second part of the CPU. The ALU performs the calculations and makes comparisons between units of data. The  last  component  is  the  Control  Unit  (CU),  the  work  of  which  is  to control the operations of the hardware for example by issuing commands to all elements of the computer as per the dictations of memory. (e.g from the input devices to memory, from memory to output devices, etc). The Central Processing Unit determines the power of a computer hardware system which is described in terms of : Size of Memory, which is measured by the number of characters of data it can store Speed of the Control and Arithmetic Logic Unit, which is measured in millions of instructions per second (MIPS). The work of the various input devices such as terminal keyboard, disk storage  units  and  tape  storage  units  is  to  send  data  into  the  CPU, whereas the work of the output devices such as printers, visual display units, disk and tape units is to give out the results from the processing operations. The Central Processing Unit also “houses” Registers. The latter is a small part in the CPU that holds data before processing or probably after. They store data to be processed and thereafter partial results. Registers are of different kinds performing different functions: Ordinary Counter Register (OC) – This register addresses the next instruction to be expected or we could say it contains the addresses of the next instruction to be Instruction Register (IR) – This register contains the actual instruction under Accumulator Register – This register stores data to be processed or the results of a partial The processor communicates with the main memory through 2 registers: Memory Address Register (MAR) Data Address Register (DAR) When reading a word from the memory, the CPU stores the address of that word in MAR and sends a read signal to a main memory. After one memory cycle, the value of the word is in DAR from where the CPU will search for it. When reading a word, the CPU stores in MAR the address of where the write operation will take place. The value to be written will be stored in the DAR and then it sends the write signal to the memory.   Execution of an Instruction The  execution  of  an  instruction  of  the  central 

Before we attempt to define a Computer, there are a number of associated terminologies that the learner needs to know beforehand. These are: Data, Information, and Programs. Data is the name given to facts. For example, in a school, the number of students in a class, the number of teachers, names of students, the name of customers in a business. Information is result from processed data. For example adding some numerical values like the numbers 14 and 17 into the computer will give you the result of 31. The later is information you required. Information can be defined as data computed into a more useful form than raw form. Program is a series of instructions written in the language of the computer for them to obey and perform specific tasks as outlined by the instructions. A Computer can therefore be defined as “an electronic machine that takes in data (facts) in the raw form, processes the data to give out in another form called information”. When a computer is fed with data, it passes through four basic steps before the data can be displaced; Input Process – the user will type the data from say the keyboard (to be introduced later in the chapter) and the computer will accept the dame and store within it. Storage Process – the data that is fed into the computer at the same time is held, even during the time of processing and after processing; it can further be stored for further reference. These data are held in computer memory. Processing – the computer will manipulate the data held within it to a more useful form – results (information). (iv) Output Process – the user is given the information he desired. The four basic processes can be summarized in the following way by looking at the same terms of information processing cycle. Organizing data for processing – to get quality results (information) you must have quality data to start with. Unreliable original data generates unreliable results. If you give a computer garbage, you get garbage in return. Its called GIGO – Garbage In – Garbage Out. Information Processing Cycle – Information Processing Cycle includes a series of steps for transforming data into meaningful information for people. A cycle is defined as a sequence of activities performed in an order that it produces expected and meaningful results. A Processing Cycle is repeated, it means, if the same resources are used in the same way, the same outcome will result. The standard cycle followed to process data and deliver information comprises of 4 major functions: Input Function – the input function gathers and collects stored data items and enter them into the system for processing. Input can come from many sources, for example from files kept in the office, banking institutions and accounts. Storage Function – this function allows the user to store data being processed in the memory of the computer as well as to store the information for future use. Processing Function – the desired operation by the user is carried out on the data keyed in and stored in the memory so as to turn it into meaningful information. Output Function – the data stored is processed and then output into files, printed as hard copies or displayed on the screen for the user. Note: For any information processing system to run smoothly on a day-to- day basis, the processing activities must be organized. A system has little work if it provides helpful information on one day and useless information the next day. Output should be useful the first time and every time for the system. 1.2 CLASSIFICATION OF COMPUTERS There are four basic ways by which computers can be classified: Physical size i.e how large the computer is. By the way they process data By purpose By use 1.2.1 Physical Size The following computer systems are categorized by how large they are: 1. Monster Computer Sometimes it is referred to as Super computers or Maxi computers. These are computer of enormous power and are very large in size. Its installation requires special floors to carry its weights and it also needs special plumbing to carry a fluid known as fluorocarbon needed to cool it. One unique feature of maxi computers is that when you purchase it, the purchase price will include the services of 2 permanent engineers to maintain it forever. They are typically used for scientific research and military applications, petroleum engineering, nuclear physics and meteorology. Examples of monster computers include CYBER and CRAY computers. For example, the whole globe needs only one monster computer to forecast weather at once. 2. Mainframe Computers Mainframe computers are second in size to monster computers. These computers perform more data processing work than any other type of computers. For this reason they form a large portion of installation in most organization. As does the monster computers, mainframe computers also have some special requirements, for the reason, they are housed in special rooms brought about by the special power that they posses together with environmental control requirements. Mainframe computers can be used by more than one person at a time since they can support a large network of other computers organizations that employ mainframe computers alongside other computers are banks, government agencies, commercial and industrial agencies. 3. Minicomputer Also called Medium sized computers. These computers compared to mainframe are smaller, slower and less expensive. A minicomputer has an advantage over the previous two in the sense that it does not have any special power or environmental control requirements. For this reason, the medium sized computer can always be located anywhere within the organization. Minicomputers can do the work that the mainframe does but on a small scale. 4. Microcomputers Of the types of computers, microcomputers are the slowest. However, they counteract this disadvantage because they are easy to use and the cost of purchase is also low. A microcomputer gets its name from the fact that its main computing component, the microprocessor (to be

Introduction In this chapter, we shall undertake a case study entitled A school canteen management system. The objective of this case study is to help the students to apply the programming techniques learnt in Form 3 Preamble A school canteen operator sells confectionaries and toiletries to the students. The canteen operator requests you to develop a canteen management system that will accomplish the following: Allow storage of stock records in a file. Enable searching of a file to retrieve a particular record for editing and adding new stock. Process sales transactions and calculate the total bill and change due to a customer. 4. Generate daily sales report showing all the items sold for a particular day. Problem recognition and definition A careful analysis of the above scenario reveals that the system will need the following tasks: Entering stock records and storing them in a file. Searching for the stock file to retrieve records. Processing of daily transactions. Recording of any sale transactions in a transaction file. Generating sales reports for a specified date.   Developing algorithms Before coding, the programmer needs to develop algorithms for each task. These algorithms will enable the programmer to develop the code for each of the processes. Algorithm for entering new stock records The new stock module should enable the user of the system to continually enter new stock records in the file until he/she is through with the process. Therefore, the computer should request the user to key in records until the last item is entered. The following pseudocode extract can be used to represent the algorithm: Output “Enter a new item?” Enter “yes” or “no” Input reply While Reply <> No Output “Enter stock item details” Write to stock file Output “Are you through with entering the records Yes/No”   Input Reply loop End While Algorithm for searching for a record This process will enable the user to access the records in a stock file and retrieve a particular record. The record search can be done as per the identification number of each record i.e. record ID. The search algorithm can be represented as follows: Begin Enter the code of the record Open stock file for reading While Not end of file Begin        If code entered = record itemcode Then        Output record details        Else        Output ‘Record not found’   End if loop End while Close file End Algorithm for processing sales Sales processing requires that the stock file be opened in order to read details of the items bought. The sales module then calculates the amount of the sale and the change owed to the customer. The module should also update the quantity of the items in stock. The following algorithm will be used: Begin Retrieve item from stock file by record ID  Specify quantity to be sold Compute bill and customer change  Save transaction in sales file END Saving a sales transaction After selling an item, the sales details must be stored in the system for future reference. In our case, the current transaction has to be stored in a file which we shall refer to as a sales file. Constructing the system in Visual Basic Open Visual Basic and create a new project called Canteen.vbp. Create five forms in the project window i.e. Form1, Form2….Form5. To create a form, simply Click Project then Add Form command. Save the forms with the following names: Form Name Form I    UserInterface Form2     AddNewStock Form3    SellItem Form4    SearchItem Form5     SalesReport   Remember while saving that all Visual Basic forms have the extension .frm. After saving, change the Name property for each form in the properties window to start withfrm e.g. frmCanteenManagementSystem for Form 1. Change the captions for each form as you proceed through the project. At the end of this activity, the forms in your project should look as shown in Figure 6.1 in the Project Explorer window. NB: Simply click the Project explorer icon to view this window. Alternatively, click View project Explorer on the menu. It is now time to start placing objects on the forms and entering the code associated to each of the objects. Creating the user-interface form Double click UserInterface.frm in the project explorer window and design it as shown in Figure 6.2. NB: Change both the Name and caption properties of the command buttons as shown below: The File menu on the form has only one command namely: Exit used to close the program when clicked. To add this menu clicks the Menu Editor icon on the toolbar. Alternatively click, Tools then select: Menu Editor Command. Create the menu as shown in Figure 6.3 of the menu editor window: To place the command buttons on the form, simply double click their icons on the toolbar. Since this is the first form that the user will see when the project is run, the various controls are meant to help the user access other forms in the project.   Adding code the “Canteen management system” form This is the main form that has commands that enable the user to access other forms. Click the File menu then command Exit. Notice that the code window for the Exit command opens on the screen. Type the word “End” in the body of the event procedure as shown below: Private Sub mnuExit – click() End End Sub This means that when the Exit command is clicked, the program will stop executing. Save and close this code window. Double click the “Add New Stock Record” button and add the code below in the body of the event procedure as shown: Private Sub cmdAddNewStock- Click() Load frmAddNewStock frmAddNewStock Show End Sub This code loads frmAddNewStock form and display it on the screen when the user clicks Add New Stock record command button. Double click the “Sell Item” button and add the following code in the body of the event procedure as shown: Private Sub cmdSellltem – Click() Load frmSellltem frmSellltem.Show End Sub Double click the

Before  we  attempt  to  define  a  Computer,  there  are  a  number  of associated terminologies that the learner needs to know beforehand. These are: Data, Information, and Programs.   Data is the name given to facts. For example, in a school, the number of students in a class, the number of teachers, names of students, the name of customers in a business. Information is result from processed data. For example adding some numerical values like the numbers 14 and 17 into the computer will give you the result of 31. The later is information you required. Information can be defined as data computed into a more useful form than raw form.   Program is a series of instructions written in the language of the computer for them to obey and perform specific tasks as outlined by the instructions.   A Computer can therefore be defined as “an electronic machine that takes in data (facts) in the raw form, processes the data to give out in another form called information”.   When a computer is fed with data, it passes through four basic steps before the data can be displaced; Input Process – the user will type the data from say the keyboard (to be introduced later in the chapter) and the computer will accept the dame and store within Storage Process – the data that is fed into the computer at the same time is held, even during the time of processing and after processing; it can further be stored for further These data are held in computer memory. Processing – the computer will manipulate the data held within it to a more useful form – results (information). Output Process – the user is given the information he   The four basic processes can be summarized in the following way by looking at the same terms of information processing cycle. Organizing data for processing – to get quality results (information) you must have quality data to start with. Unreliable original data generates unreliable  results. If  you  give  a computer  garbage,  you  get  garbage  in return. Its called GIGO – Garbage In – Garbage Out.   Information Processing Cycle – Information Processing Cycle includes a series of steps for transforming data into meaningful information for people.   A cycle is defined as a sequence of activities performed in an order that it produces expected and meaningful results.   A Processing Cycle is repeated, it means, if the same resources are used in the same way, the same outcome will result. The standard cycle followed to process data and deliver information comprises of 4 major functions: Input Function – the input function gathers and collects stored data items and enter them into the system for Input can come from many sources, for example from files kept in the office, banking institutions and accounts. Storage Function – this function allows the user to store data being processed in the memory of the computer as well as to store the information for future Processing Function – the desired operation by the user is carried out on the data keyed in and stored in the memory so as to turn it into meaningful Output Function – the data stored is processed and then output into files, printed as hard copies or displayed on the screen for the user.   Note: For any information processing system to run smoothly on a day-to- day basis, the processing activities must be organized. A system has little work if it provides helpful information on one day and useless information the next day. Output should be useful the first time and every time for the system.