FUNDAMENTALS OF COMPUTER CHAPTER# 01 Short / Detailed Question Answers

 COMPUTER SCIENCE 9TH - Short / Detailed Question Answers

FUNDAMENTALS OF COMPUTER
CHAPTER# 01
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Q.1: What is Computer?
Ans: A computer is an electronic data processing machine or device that performs processes, calculations and operations based on instructions provided by a program.

Q.2: Discuss the use of computer in any two fields of life.
Ans: Computers are now used vastly in every field of life. The advancement in computer caused advancement in knowledge, science and technology. Today, computers are used in fields of business, industry, education, banking, transportation, research, explorations, media, entertainment, etc.

Use of Computers in Education:
Computer technology has had a deep impact on education. Because of computers, education has become easier and much more interesting than before.

The main uses of computer in education are as follows:

(i) Computer teaching plays a key role in the modern education system. Students find it easier to refer to the Internet than searching for information in fat books. The process of learning has gone beyond learning from prescribed textbooks. Internet is a much larger and easier-to-access storehouse of information.

(ii) When it comes to storing retrieved information, it is easier done on computers than maintaining hand-written notes.

(iii) Computer technology has made the dream of distance learning a reality. Education is no longer limited to classrooms. It has reached far and wide.

(iv) Computers facilitate effective presentation of information. Computers facilitate audio-visual representation of information, thus making the process of learning interactive and interesting. Computer-aided teaching adds a fun element to education.

(v) The Internet can be used to refer to information on different subjects. Both teachers and students benefit from the Internet. Teachers can refer to it for additional information and references on the topics to be taught.

(vi) Computers enable storage of data in electronic format, thereby saving paper. Memory capacities of computer storage devices enable them to store huge chunks of data.

Use of Computers in Medical Sector:

Computers are excellent means for storage of patient-related data. Big hospitals employ computer systems to maintain patient records. It is often necessary to maintain detailed records of the medical history of patients. Doctors often require the information about a patient's family history, physical ailments, already diagnosed diseases, and prescribed medicines.

Medical journals, research and diagnosis papers, important medical documents, and reference books can best be stored in an electronic format.

Many of the modern-day medical equipment have small, programmed computers. Many of the medical appliances of today work on pre-programmed instructions. The circuitry and logic in most of the medical equipment is basically a computer.

Computer software is used for diagnosis of diseases. It can be used for the examination of internal organs of the body. Advanced computer-based systems are used to examine delicate organs of the body. Some of the complex surgeries can be performed with the aid of computers. The different types of monitoring equipment in hospitals are often based on computer programming.

Medical imaging is a vast field that deals with techniques to create images of the human body for medical purposes. Many of the modern methods of scanning and imaging are largely based on computer technology. Magnetic resonance imaging and tomography employ computer software.

In the field of medicine, computers allow for faster communication between a patient and a doctor. Doctors can collaborate better over the Internet. Today, it is possible to obtain expert opinions within seconds by means of the Internet.

Medical practitioners can discuss medical issues in medical forums. They can exchange images and messages in seconds and derive conclusions speedily. They can seek advice and share knowledge in a convenient manner over the Internet. The importance of computers cannot be stressed enough as computer technology has revolutionized the field of medicine.

Q.3: Describe the mechanical era of computer evolution.
Ans: Mechanical Era (Dark Age):
Men have been trying to invent machines that can solve mathematical problems. In the mechanical era, humans became successful in making simple machines that could help perform simple arithmetic operations, in other words, computing. These machines were manually operated since electricity was not invented. Some of the important machines of this era are:

• (a) Abacus (3000 B.C.):
  Abacus was invented about 5000 years ago. It is also known as a counting frame. Abacus is still used to teach basic arithmetic operations to students. Abacus is considered the first computer prototype.

• (b) Napier's Bones (1612 A.D.):
  Scottish mathematician John Napier developed Napier's Bones in 1612. It is also called Napier's Rods. It was a small machine that contained ten rods. The rods were made up of bones, wood, or metal. Napier's Bones was used for multiplication and division.

• (c) Slide Rule (1622 A.D.):
  English mathematician William Oughtred invented the Slide Rule. This was basically a pair of two moveable rules placed side by side. They had a standardized set of markings called scales. These scales were used for mathematical computations. Slide Rule was used to multiply and divide numbers. The modern slide rules are still used in some countries.

• (d) Pascaline or Pascal’s Calculator (1642 A.D.):
  French mathematician Blaise Pascal invented a mechanical calculator known as Pascaline. He developed this machine to help his father, who was a tax collector. Pascaline can perform addition and subtraction by eight figures. The user had to adjust wheels to perform calculations.

• (e) Leibniz's Calculator (1694 AD.):
  Leibniz's Calculator was developed by the German mathematician Gottfried Wilhelm Leibniz. It was also called stepped reckoner. It was the first calculator that could perform all four basic arithmetic operations: addition, subtraction, multiplication, and division.

  (f) Babbage’s Difference and Analytical Engines (1822 and 1837 A.D.):
  Charles Babbage was an English mathematician and mechanical engineer. He is known as the Father of Computer because he developed the first complete computing machine. His first invention was the Difference Engine. It was an automatic mechanical calculator. The Difference Engine was a large machine, made of metal, and was powered by steam. The Difference Engine had storage (mechanical memory) that could hold data temporarily for processing and to store results. It was used to allow a user to enter calculations and get printed results. The Difference Engine worked on difference equations.

  Then, Charles Babbage designed but could not build a very big machine in 1837. This was named the Analytical Engine. The proposed design included an ALU as its basic computational flow control. It was programmed using punched metal cards and contained integrated memory. Historians consider it to be the first design concept of a general-purpose computer because of its comprehensive design.

  Images:

1. Babbage's Difference Engines
2. Analytical Engines

Q.4: Name the eras of evolution of computers.
Ans: Eras of Evolution of Computers:
The computers which we see today are modern shape of computers which have been evolved since centuries. The evolution of computers is generally divided in following three eras.

(i) Mechanical Era. (Dark Age)
(ii) Electro-Mechanical Era (Middle Age)
(iii) Electronic Era (Modern Age)

Q.5: Describe the electro-mechanical era of computer evolution.
Ans: Electro-Mechanical Era (Middle Age):
This era starts from the mid of 19th century. In this era scientists became able to develop faster and more accurate computing machines as they were powered by steam and electricity. One of such machines was Tabulating Machine.

Herman Hollerith’s Tabulating Machine (1890 A.D.):
It was invented by American inventor Herman Hollerith in 1890. Hollerith’s tabular first machine was used for the U.S. 1890 Census. Because of Hollerith’s tabulating machine census data took only six months to compile, which was very fast as compared to previous U.S. census in 1880 which took 7 years to be completed. Hollerith Tabulating Machine became very famous and used in many offices of U.S. Government. His tabulating machine could read and sorted out data from punched cards.

Q.6: Describe the electronic era of computer evolution.
Ans: Electronic Era (Modern Age):
The advancement in the vacuum or electron tube gave birth to the electronic era. In this era the true computers were invented which worked on the principle of input, store, process and output. Continuous advancement in electronic engineering increased deficiency and speed of computers considerably. The electronic era may be categorized in generations on the basis of core technology used to build computers.

• The First Generation of Computers (1940 to 1956)
• The Second Generation of Computers (1956 to 1963)
• The Third Generation of computers (1964 to 1971)
• The Fourth Generation of computers (1971 to Present)
• The Fifth Generation of Computers (Present and Beyond)

Q.7: Describe the characteristics of the first generation of computers and its main features.
Ans: First Generation of Computers (1940 to 1956):
Based on vacuum tubes, first generation computers were very large in size. This generation used machine language (i.e. 1’s and 0’s). Magnetic drums were used as primary internal storage medium and punched cards for input. In this generation mainly batch processing operating system was used. Computers of this generation were primarily used for scientist and research purposes. Electronic Numerical Integrator and Calculator (ENIAC), Universal Automatic Computer (UNIVAC) are examples of first generation computers.

Main Features:

• Technology Used: Vacuum Tubes
• Size: Very large in size (Main frame)
• Language: Low level Machine language (i.e. 1's and 0's).
• Main memory (primary internal storage): Magnetic drums
• External storage: Punched card
• I/O Device: Punched cards and paper
• Operating system: Batch processing operating system (i.e. human operators to set system, no proper operating system)
• Use: Scientific and research purpose.
• Example: ENIAC, EDVAC, UNIVAC

Q.8: What do you know about the second generation of computers and its main features?
Ans: Second Generation of Computers (1956 to 1963):
Because of transistors computers became smaller, faster, cheaper and more efficient. Assembly language and a high-level language FORTRAN were introduced. Magnetic core was used as primary internal storage medium.

Punched Cards were used for input. Batch processing and Multiprogramming Operating systems were used. These computers were mainly used for commercial productions, scientific and engineering analysis and design. Examples are IBM 7094 and IBM 1401.

Main Features

• Technology Used: Transistors.
• Size: smaller and faster (main frame), cheaper and more efficient.
• Language: Assembly language and a high language FORTRAN
• Main memory (internal storage): Magnetic core (RAM and ROM)
• External storage: Magnetic tapes and magnetic disk

Q.9: Briefly describe the third generation of computers and its main features.
Ans: Third Generation of Computers (1964 to 1971):
Use of ICs further decreased size of computers and increased the speed and efficiency. Less expensive computers were introduced. High level programming languages such as Pascal and COBOL were used. Keyboard as input and monitor as output also eased the use of computer. Time sharing and Real-time Operating Systems were used. The use of computers was extended to database management and automatic industrial control. IBM 360 and IBM 370 are the examples of this generation’s computers.

Main Features

• Technology Used: Integrated Circuits (ICs).
• Size: Mini (decreased size and increased the speed and efficiency, less expensive)
• Language: High level programming languages such as Pascal and COBOL
• Main memory (internal storage): PROM and DRAM
• External storage: Floppy disk
• I/O Device: Keyboard (input), Monitor (output)
• Operating system: Time sharing and realtime (Unix operating system)
• Use: The use of computers was extended to database management and automatic industrial control
• Example: IBM 360 and IBM 370, TDC-316

Q.10: Describe the characteristics of the fourth generation of computers.
Ans: Fourth Generation of Computers (1971 to Present):
The invention of microprocessors was revolutionary which caused the development of faster, less expensive, smaller and more reliable computers. They used semi-conductor memories RAM and ROM and magnetic storage became popular. More high-level languages were introduced like C, C++, Java, etc. These computers are used in almost every field of life, like space applications, business and art work.

Time sharing, real time and distributed operating system are used. This generation also saw the development of graphics User Interfaces (GUTs). Examples are Apple Macintosh, IBM PC.

Main Features

• Technology Used: Microprocessors.
• Size: micro computer (faster, less expensive, smaller and more reliable)
• Language: More high languages like C, C++, Java etc.
• Main memory (internal storage): Semi-conductor memories RAM and ROM (EPROM and SRAM)
• External storage: Magnetic storage
• I/O Device: Monitor (output)
• Operating system: Time sharing, real time and distributed operating system, with development of Graphical User Interfaces (GUIs) (DOS and UNIX)
• Use: in every field of life like space applications, business and art work.
• Example: Apple Macintosh, IBM PC.

Q.11: What do you know about the fifth generation of computers?
Ans: Fifth Generation of Computers (Present and Beyond):
Fifth Generation computing devices are still being developed. In this generation, computers will be capable of self-learning, reasoning and generalization. These computers or controlled machines like robot will also be able to process human language. The branches of AI include: Machine Learning, Deep Learning, Natural Language Processing, Robotics and Expert Systems.

Main Features

• Technology Used: Artificial Intelligence Technology, still being developed
• Size: very tiny in size
• Language: AI (Artificial Intelligence) includes; Machine Learning, Deep Learning. Natural Language Processing, Robotics and Expert Systems. These computers or controlled machines like robot will also be able to process human languages.
• Main memory (internal storage): EEPROM, SIMM, DIMM
• External storage: Modified magnetic and optical disk etc
• I/O Device: Keyboard, pointing device, scanner (input) Monitor, printer (output) etc.
• Operating system: GUI based, Microsoft windows 95 and onward, Windows NT.
• Use: In all fields of life. Computers will be capable of self-learning, reasoning and generalization.
• Example: laptop, notebook, digital diary, Android, Pocket PC, Palm top, Humanoid Robots

Q.12: Describe artificial intelligence with examples.
Ans: Artificial Intelligence (AI):
Artificial intelligence (AI) is a wide-ranging branch of computer science concerned with building smart machines capable of performing tasks that typically require human intelligence. AI is an interdisciplinary science with multiple approaches, but advancements in machine learning and deep learning are creating a paradigm shift in virtually every sector of the tech industry. There are many different fields of AI, including 'robotics,' but one of the most commonly known forms is referred to as 'machine learning.' This involves a program applying known information to new experiences and 'learning' how to take this historical information and its experiences into account in future actions. Machine learning can find patterns in large amounts of data that humans might otherwise miss.

Examples of Artificial Intelligence:

(i) A Bedford, Mass. company made a smarter home robot, Roomba 980. The Roomba 980 model uses artificial intelligence to scan room size, identify obstacles and remember the most efficient routes for cleaning. The self-deploying Roomba can also determine how much vacuuming there is to do based on a room’s size, and it needs no human assistance to clean floors.

(ii) A Hong Kong-based company made a humanoid robot, Sophia. Sophia is an incredibly advanced social-learning robot. Through AI, Sophia can efficiently communicate with natural language and use facial expressions to convey human-like emotions.

(iii) A Boston-based company made an AI-powered machine for pathologists. The company’s machine learning algorithms help pathologists analyze tissue samples and make more accurate diagnoses. The aim is to not only improve diagnostic accuracy, but also treatment. Path AI’s technology can also identify optimal clinical trial participants. Path AI has worked with the Bill & Melinda Gates Foundation and Philips to develop high-volume prognostic test support tools and plans for sustainable access to their advanced diagnostic services.

Uses of Artificial Intelligence:

• A.I. is also used for Machine Learning. It learns from our daily routines and suggests us different options. Like Google Maps suggests the best ways for our daily commute.
• A.I. is vastly used in scientific experiment, healthcare, and space technologies.

Q.13: Write down the names of different ways of computer classification.
Ans: Classification of Computers:
Computers can be classified into differentials as shown below:

Classification of Computers

• Technology / Type of Data Handled

  • Analog
  • Digital
  • Hybrid

• Size

  • Super Computer
  • Mainframe Computer
  • Mini Computer
  • Micro Computer

• Purpose

  • General Purpose
  • Special Computer

Q.14: Describe the classification of computers according to technology.
Ans: Classification of Computers According to Technology
According to technology or type of data they handle, computers are classified into three types.

(a) Analog Computers:
Analog Computers are used to process analog data. Analog data are in the form of continuously varying physical quantities like pressure, temperature, voltage, speed, and weight.
Examples of Analog computer are speedometer of a car, voltmeter, etc.

(b) Digital Computers:
Digital Computers are the most commonly used type of computers. They are used to process information with quantities using the binary number system (0’s and 1’s). Digital Computers are used in home, educational institutes, offices, business, scientific fields, etc.

(c) Hybrid Computers:
Hybrid Computers are the combination of Analog and Digital Computer systems. These computers combine analog and digital features of computers in a single machine. A Hybrid Computer uses analog to digital and digital to analog conversion. It may input or output either digital or analog data.

Q.15: How can we classify computers according to their sizes?
Ans: Classification of Computers According to Size:
Computers are also divided into four groups according to their size.

(a) Super Computers:
Super Computers are the most powerful, fastest, and largest computers. They are extremely expensive. These computers are widely used in scientific applications such as aerodynamics, design simulations, processing of geological data, weather forecasting, and nuclear research.

(b) Mainframe:
Mainframe Computers are powerful multi-user and multi-processor computers. They can process a huge amount of calculations at a very high speed. Mainframes are also very expensive and require a lot of technical expertise to be installed and operated. They are used in banks and many large business organizations where several users work simultaneously.

(c) Minicomputer:
These are smaller than mainframe computers, but they are more powerful than microcomputers. Minicomputers usually use a multi-user operating system. Multiple users can use the minicomputers through terminals. Minicomputers may be used as network servers and internet servers. DEC VAX and IBM AS/400 are good examples of minicomputers.

(d) Microcomputers:
Microcomputers are also called Personal Computers (PCs). The use of microprocessors has made computers cheaper yet faster and more reliable. These are the smallest computers designed to be used by individuals. PCs can be used for a variety of tasks like documentation, calculations, illustration, and entertainment. The power of network and internet has also made it more useful. Now computers are also used for communication and socialization.

Q.16: Describe the classification of computers according to purpose.
Ans: Classification of Computers According to Purpose:
According to purpose, computers are either general purpose or special purpose.

(a) General Purpose Computers:
Most computers in use today are General Purpose Computers. These computers can process a variety of tasks. These computers can store and execute different programs in their memory. Therefore, various tasks like word processing (typing & editing), payrolls, accounts, inventory control, manipulating facts in a database, making scientific calculations and statistical data analysis, and controlling the security system of an organization are achieved by these computers. Desktops, laptops, tablets, and smartphones are examples of General Purpose Computers.

(b) Special Purpose Computers:
As the name states, Special Purpose Computers are designed to perform specific tasks. Special Purpose Computers repeatedly perform a single job more efficiently. They are also known as Dedicated Computers. These computers are useful in traffic lights control systems, gravitational systems, aviation, weather forecasting, satellite tracking, and ATMs.

Q.17: Explain the uses of computers in different fields of life.
Ans: Role and Uses of Computers:
The role of computers in our lives is increasing day by day. Different aspects of the changing role of computers are as follows:

Computers in Different Fields of Life:
We are living today in the information era, and information has become one of the most valuable assets. To process this information, we make use of computers in various fields in our daily life. Computers have been integrated into our life in different shapes and sizes like desktops, laptops, mobile phones, gaming consoles, and smart devices. Our lives have become so dependent on computers that we cannot work even a single day without the help of it. We have automated many of the repetitive tasks with the help of more advanced, faster, and accurate computers and brought our routine tasks, office work, businesses, research, and industrial applications to a new level.

Computers are largely used in every field of life. Manufacturing, e-commerce, education, medical, banking, communication, entertainment, engineering, agriculture, architecture, business, defense, and sports are highly influenced by computers. 

Computers in Today's World:
21st century is the era of technological revolution. In the past technology was only used to access and share information. However, with the passage of time, the rapid change in technology has made it nearly impossible to perform any human activity without its use. Computers are playing an important part in our daily life. News, weather updates, travelling information and bookings, money transfer and even taxi bookings are done with the help of mobile phone apps. Many managerial tasks are also done by computer software. School, library and hospital management are some examples. Online shopping is becoming a trend in our society too.

Computers are also providing a variety of choices for entertainment like online games in which players from different parts of the world can participate simultaneously. 3D graphical software has given a new look to movies in which different comic characters can act with human actors. Photo, sound and video editor software not only help artists and singers to produce extraordinary creations but also inexperienced people can enjoy their productivity with ease of use.

Q.18: Discuss the emerging computer technology for tomorrow's world.
Ans: The emerging technologies are also getting better day by day and we can imagine how computer will be used in future. Artificial intelligence, robotics, wireless communication and virtual realities are some areas which are shaping the modern world.

Artificial Intelligence:
Artificial Intelligence is based on simulating human intelligence in machines that can easily mimic and execute tasks from simple to more complex operations. The term AI may also be referred to any machine that displays qualities associated with a human brain such as learning, reasoning, and problem solving. AI is also used for machine learning. It learns from our daily routines and suggests us different options. Like Google maps suggest the best ways for our daily commute. AI is vastly used in scientific experiment, healthcare and space technologies.

Robots:
Robots are the machines that can be controlled by a computer and are capable of carrying out a complex series of actions automatically. Robots can be controlled by an external control device or through programming. Robotics deals with designing, creating and programming of the robot and enhancing it by taking sensory feedback and processing information. Robots are commonly used in manufacturing, industry, science, medicine and education.

Wireless Communication:
Wireless Communication has become an integral part of our lives. Wireless communication technology transmits information using electromagnetic waves like IR (Infrared), RF (Radio Frequency), satellite, etc. Global Positioning System (GPS) is now used to find real-time location of people and objects. Smart phones that include 3G, 4G and 5G networks have transformed the conventional use of telephones. These phones not only provide better coverage but also fast mobile internet experience. Wireless Communication is also giving new meaning to socialization and human interactivity.

Virtual Reality:
Virtual Reality is an artificial environment that is created with software and presented to the user in a way that the user feels it as a real environment. Virtual reality can be used for the simulation of a real environment for training and education. It is also used for the development of an imagined environment for a game or interactive story.

Q.19: Discuss the scope of the different careers in IT sector.
Ans: Careers in IT Field:
Today Computer Science plays a key role in all fields of life. Computer Science (CS) jobs are ranked as having some of the highest salaries in the world. It’s no surprise that computer science and information technology (IT) are changing tomorrow’s job market. Let’s look at different careers that are present in the IT sector.

(i) Software Engineer:
A Software Engineer is a person who uses different programming languages to develop software products like games, learning management system (LMS), business applications, educational and entertainment software.

(ii) Network Administrator:
A Network Administrator is an IT expert who manages an organization’s network. He or She is responsible for installing, maintaining and upgrading any software or hardware required to efficiently run a computer network.

(iii) Database Administrator:
A Database Administrator (also known as DBA) is a skilled professional who maintains a secure database environment in an office, business or organization.

iv) Web Designer:
Web is short for World Wide Web or www. This is another name for internet. Web designers are people who build websites. They prepare a site’s content with eye-catching designs, attractive images and strong text. They rely on many web designing tools to ensure an interactive website. How the site works and how it looks is the responsibility of web designers. They are also responsible for maintaining and updating an existing site.

(v) Graphic Designer:
Graphic is another word for image. Graphics Designers develop overall layouts of brochures, magazines and other types of published advertisements and documents. They do this by using various computer graphics software. This task is usually accomplished by combining art and technology, conveying ideas through images, layout of websites and printed matter.

(vi) Information Security Analyst:
These people protect networks... They plan and carry out security measures to ensure that no loss of data (or information) occurs. We can call them the police force of the internet. Computer hackers are always on the lookout for customer account details that they can use to steal money. Information Security Analysts ensure that no such theft occurs.

(vii) Computer Science or IT Teacher:
Another very rewarding career for Computer Science graduates and post-graduates is teaching in schools, colleges and universities. These instructors instill in their students the importance of computers in today’s world, and the impact these machines will have in their later lives.

Q.20: Describe computer hardware and their functions.
Ans: Computer Hardware:
Computers consist of software and hardware. Software is the programs and applications that run on computer. Hardware is the physical parts of the computer that run programs and applications. Hardware can be seen and touched while software cannot. Computer hardware is a collection of all the physical parts or components of a computer.

It includes the computer casing, the CPU or Central Processing Unit, computer memory, VGA graphics card, sound card, and the motherboard.

System Unit:
A System Unit is the part of a computer that contains the primary devices. The system unit performs operations and produces results for complex calculations. It includes the motherboard, CPU, RAM and other components, as well as the case in which these devices are enclosed.

(i) Motherboard:
The motherboard is the main board which connects different parts of the computer. It includes the following general components: Microprocessor (CPU), Slots, Ports, Buses, RAM, ROM and other electronic components for example resistors, capacitors, diodes, transistors, jumpers etc. Just like nervous system it allows communication between all parts of the computer. We can find CPU, memory slots, expansion slots and a number of chipsets on motherboard. Motherboards are made of layered fiberglass. These layers contain copper lines that form the circuitry by which electrical signals are provided to all parts of computer. Various components of computer may be attached, detached and upgraded on motherboard according to need of the user. Motherboards also have connectors called ports. These ports are used to connect input, output and other peripheral devices.

(Image labels for motherboard components):

• Northbridge (with heatsink)
• Southbridge
• IDE Connector (x2)
• AGP Slot
• DRAM Memory Slot (x2)
• PCI Slot (x5)
• CMOS Backup Battery
• 20-pin ATX Power Connector
• Connectors for Integrated Peripherals (PS/2 Keyboard and Mouse, Serial Port, Parallel Port, USB (x8), Ethernet, audio (x2))
• CPU Fan & Heatsink Mounting Points
• CPU Socket

(ii) Microprocessor (CPU):
CPU or microprocessor is the brain of the computer. The microprocessor is a chip containing millions of tiny transistors. These transistors manipulate data. Microprocessor performs all the calculations necessary to make the computer work. These calculations are performed at very high speed and accuracy. Microprocessor is made up of silicon. The microprocessor fetches, decodes, executes and stores all the instructions given by the user or any other device. The speed of the computer mainly depends upon the speed of the microprocessor. A microprocessor that has faster clock speed (measured in GHz) and more cores and cache works faster.

Q.21: Describe the components of a microprocessor.
Ans: There are typically five components of a microprocessor.

(a) Arithmetic Logic Unit (ALU):
ALU performs all the actual calculations like arithmetic operations and logical comparisons. Arithmetic operations include addition, subtraction, multiplication, and division while logical comparisons include comparing, selecting, and matching of data.

(b) Control Unit (CU):
Control Unit is responsible for controlling the transfer of data and instructions among other units of a computer. This unit controls the operations of all parts of the computer but does not carry out any actual data processing operations. CU functions just like a traffic policeman. It manages and coordinates all the units of the computer.

(c) Clock:
Clock generates pulses, and instructions are executed on the basis of pulses. Clock speed is measured in MHz and GHz.

(d) Registers:
It is a temporary storage area that holds the data that is being processed. It is also known as a programming model which may be of 8 bits, 16 bits, 32 bits, or 64 bits.

(e) Cache:
Cache is an intermediate storage area, which is available inside the microprocessor. The immediate processed information is stored in cache. The cache inside the microprocessor is called internal cache and outside is called external cache.

Q.22: List any five components present on motherboard.
Ans: List of Components Present on Motherboard:
Microprocessor (CPU), Slots, Ports, Buses, RAM, ROM, and other electronic components, for example, resistors, capacitors, diodes, transistors, jumpers, etc.

Q.23: Write a note on input devices.
Ans: Input Devices:
Input devices are used to enter data into computers. These devices can be categorized into Text Entering, Pointing, and Image Scanning Devices.

(i) Text Entering Devices:
Keyboard:
It is the most common text entering device and is used to enter data usually in text format or to perform other controlling functions. When a key is pressed, the keyboard controller chip sends its corresponding code in a keyboard buffer called scan code, which is processed by the CPU.

(ii) Pointing Devices (Mouse and its Variants):
They are used for the quick movement of the cursor on the screen needed usually in graphic mode. It includes mouse, joystick, trackball, and trackpad.

(iii) Image Scanners:
Scanners convert images into electronic format understandable by computers through light sensing. They also work on Optical Recognition which occurs when a device scans a clear printed surface and translates the image into machine-readable formats that a computer understands. Image scanners include Optical Mark Recognition (OMR), Optical Barcode Reader (OBR), and Optical Character Recognition (OCR).

(iv) Other Types of Input Devices:
There are also other input devices. For example, microphones are used to accept sound input and convert it into a digital audio format. Microphones are also used for voice recognition, which can convert voice input into text files. Touch Screen is also used for input. It accepts input directly on the monitor by touching a finger or any object on the screen. Magnetic Ink Character Recognition (MICR) and Magnetic Strip Reader are also used for input.

Q.24: What do you know about output devices?
Ans: Output Devices:
A hardware device that sends data from a computer (CPU) to another device or user is called an output device. The most common output devices of a computer are monitor and printer. There are two types of output devices.

(i) Soft Copy Output Devices:
It is screen display or voice output. It is volatile output and lost when other output is shown or computer is turned off. Following are some of the devices used to give output in soft form.

(a) Monitors:
It is TV-like device that displays data by small bright dots called pixels. Monitors are of two types:

• Cathode Ray Tube (CRT)
• Flat Panel Display (FDP)

(b) Data Projectors:
Data projectors are used to show colorful slides and images directly from a computer disk on a wall or large screen through an optical lens. They are also called digital light projectors and video projectors.

(c) Speakers:
Speakers give output in the form of sound. They are good for people with visual disabilities or where display is not easy.

(ii) Hard Copy Output Devices:
It is output on paper. It is nonvolatile output that is relatively stable and permanent form. Hard Copy Output Devices are:

(a) Printers:
They usually give output on paper and can print both text and graphics. There are two types of printers:

• Impact
• Non-impact

(b) Plotters:
Like printers, it gives images on paper but is typically used to print large-format images such as maps, construction drawings, advertising hoardings, etc.

Q.25: What are buses in computer? Define the types of buses.
Ans: Buses:
In computer, Buses are the electric paths on which data is sent and received by different components. They are just like roads. As roads connect different places, buses connect all the parts of the computer to each other. They also connect all internal components on the motherboard. There are three types of buses:

(i) Control bus
(ii) Data bus
(iii) Address bus

(i) Control Bus:
Control Bus carries command between different components to control all activities in a computer.

(ii) Data Bus:
It carries data between the processor, memory unit and other components.

(iii) Address Bus:
It carries the address of the data (but not the data). The address bus is used to specify memory location to be used by micro-process for specific operation.

Q.26: Which monitor will you prefer in your school: CRT or FPD? Why?
Ans: I prefer FPD (Flat Panel Display) because

(i) they take up less desk space and their prices continue to drop.
(ii) FPDs are more susceptible to accidental or deliberate damage
(iii) FPDs have more lifetime than CRT.
(iv) FPDs are, on average, brighter than CRTs.
(v) An inexpensive FPD may have a better contrast ratio than an excellent CRT monitor.
(vi) Those big CRT monitors also produce a lot of heat, which wastes energy.
(vii) FPDs consume less power and this can lead to a considerable reduction in the power bill.

Q.27: Define computer software. Write the names of its types.
Ans: Computer Software:
Software is a set of instructions that a computer uses to perform a task. It is a general term for a computer program. There are two main types of software:

(i) System Software
(ii) Application Software

Q.28: Discuss Impact and Non-impact Printers with examples.
Ans: Impact and Non-Impact Printers are two categories of the printer. Impact printers involve mechanical components for conducting printing. While in Non-Impact printers, no mechanical moving component is used.

Impact Printers:
It is a type of printer that works by direct contact of an ink ribbon with paper. These printers are typically loud but remain in use today because of their unique ability to function with multi-part forms. An impact printer has mechanisms resembling those of a typewriter.

Examples of Impact Printers:
Dot-matrix printers, Daisy-wheel printers, and line printers.

Non-Impact Printers:
It is a type of printer that does not hit or impact a ribbon to print. They used laser, xerographic, electrostatic, chemical, and inkjet technologies. Non-impact printers are generally much quieter. They are less likely to need maintenance or repairs than earlier impact printers.

Example of Non-Impact Printers:
Inkjet printers and Laser printers.

Diagram:
Impact and Non-Impact Printer

Q.29: What is the difference between impact and non-impact printers?
Ans: Difference between Impact and Non-Impact Printers:

Impact Printer	Non-Impact Printer
Produces characters and graphics on a piece of paper by striking it is called impact printer	A type of printer that produces characters and graphics on a piece of paper without striking.
It prints by hammering a set of metal pin or character set.	Printing is done by depositing ink in any form.
Electromechanical devices are used	No electromechanical device is used.
Faster speeds around 250 words per second.	Slower speeds around 1 page per 30 seconds.
Have banging noise of needle on paper	Works silently
Dot-matrix printer, Daisy wheel printers, line Inkjet printers, photo printers, laser printers are examples.	Inkjet printers, photo printers, laser printers are examples.

Q.30: Describe storage devices and its types.
Ans: Storage Devices:

A storage device refers to a hardware used to store information. There are two types of storage devices: Primary and Secondary.

(i) Primary Storage Devices:
Primary storage devices are used by computer during processing. They are quite smaller in storage capacity. Most primary storage devices are found inside the computer, and they have the fastest access to data. Primary data include RAM and ROM.

• ROM: ROM is the Read Only Memory. It is permanent memory. ROM is quite small in capacity. It stores the major setting of computer permanently.
• RAM: RAM is Random Access Memory. RAM is volatile means it loses its content as the power supply is disconnected. This is used to store data and instructions temporarily.

(ii) Secondary Storage Devices:
Secondary storage devices have a larger storage capacity and can store data permanently. Users save their data on secondary storage devices. Hard Disk, CD and DVD, SD Card and USB flash disk are examples of secondary storage devices.

Example: Hard Disc, Secure Digital Card, Pen Drive, DVD, CD.

Q.31: Describe the basic operations of a computer.
Ans: Basic Operations of a Computer:

A computer is a machine that acts according to the instructions given by the user. A computer performs four basic operations: input, processing, output and storage.

(i) Input:
Computer input has many forms. It can be from a command entered using a keyboard or a mouse. It can be data sent from another computer on a network.

(ii) Processing:
Processing is done inside the computer by CPU. Processing is the conversion of input into output. After processing, data is turned into meaningful information. This is carried out with the help of arithmetic and logical operations.

(iii) Storage:
Storage refers to the holding or saving data. RAM, ROM and Hard Disk are the devices that are used for storage.

(iv) Output:
Output is the result of a computer processing. Output may be viewed on a monitor screen, heard through speakers or printed on paper. Here, monitor screen, speakers and printer are called output devices.

Diagram:

The diagram shows the flow of data and control signals in a computer system, involving the CPU, Control Unit, ALU (Arithmetic Logic Unit), Memory Unit, and Input/Output units.

• Flow of data & instructions (data Signal): Represented by solid lines.
• Control Signal: Represented by dashed lines.

Q.32: Define and explain system software and its types.
Ans: System Software:

System software is a computer program that coordinates all activities and functions of a computer. It also controls all the operations of the computer hardware. It includes operating systems, device drivers’ utility programs and language translators.

(i) Operating System:
Operating system is the master control program that manages all the system resources. It creates an interface between computer system and user. Windows and Linux are commonly operating systems.

(ii) Device Drivers:
Device drivers are computer programs that control a particular device when it is connected to a computer. Any hardware that we have in our computer must have a device driver to communicate with operating system. A device driver is a translator between the operating system and the hardware device. For many devices, operating system has drivers pre-installed in them. This gave rise to the concept of plug and play, where the device would be attached to the computer and the operating system will instantly recognize it. A non-plug-and-play device would require you to go through several steps of installing drivers and setting up the device before it would work.

(iii) Utility Programs:
Utility means being useful. Utility programs are useful computer programs that help to manage, maintain and control computer resources. Operating systems usually have pre-installed programs that can serve the purpose, but utility software provides further functionality. One example of utility program is an antivirus software. This computer program helps to protect a computer from viruses and other harmful files.
Hard Disk tools are also part of utility programs. They manage hard disk drives and other storage devices. This includes utilities to scan the hard disks for any potential problems. Disk cleaner utility is used to remove any unnecessary files while disk defragmenter is used to re-organize file on a hard disk drive to increase performance of disk.

(iv) Language Translators:
Language Translators are used to translate human readable instructions into machine language. Computer can only understand machine language which is composed of 0’s and 1’s. The computer languages are used to make computer programs (software). Generally, software is written in high-level languages, using natural language words. Language translator are of three types: assembler, compiler and interpreter.
(a) Assembler:
The assembler translates the program written in assembly language into machine language instructions for execution.

(b) Compiler:
It translates the entire high-level language program at once into machine language before it is executed.

(c) Interpreter:
It translates the high-level language program line by line into machine language.

Q.33: Difference System and Application Software.
Ans. Difference Between System and Application Software

S No	Key	System Software	Application Software
1.	Definition	System Software is the type of software which is the interface between application software and system.	On the other hand application software is the type of software which runs as per user request. It runs on the platform which is provided by system software.
2.	Development language	In general System software are developed in low level language which is more compatible with the system hardware in order to interact with.	While in case of Application software high level language is used for their development as they are developed as some specific purpose software.
3.	Usage	System software is used for operating computer hardware.	On the other hand application software is used by user to perform specific task.
4.	Installation	System software are installed on the computer when operating system is installed.	On other hand application software are installed according to user’s requirements.
5.	User interaction	As mentioned in above points system hardware so less or no user interaction available in case of system software.	On other hand in application software user can interacts with it as user interface is available in this case.
6.	Dependency	System software can run independently. It provides platform for running application software.	On other hand in application software can’t run independently. They can’t run without the presence of system software.
7.	Example	Some examples of system software’s are compiler, assembler, debugger, driver, etc.	On other hand some examples of application software’s are word processor, web browser, media player, etc.

Q.34: Differentiate compiler and assembler?
Ans. Difference between Compiler and Assembler

S No	Key	Compiler	Assembler
1.	Operation	Compiler translates high-level programming language code to machine level code.	Assembler converts the assembly level language to machine level code.
2.	Input	Source code in high-level programming language.	Assembly level code as input.
3.	Conversion type	Compiler checks and converts the complete code at one time.	Assembler generally does not convert complete code at one time.
4.	Components	Lexical analyzer, Syntax analyzer, Semantic analyzer, Code optimizer, Code generator, and Error handler	Assembler does work in two passes.
5.	Output	Mnemonic version of machine code.	Binary version of machine code.
6.	Examples	C, C++, Java compilers.	GAS, GNU assemblers.

Q.35: Write the use of these storage devices: Hard Disk, USB Flash Disk, SD Card.
Ans: Uses of Hard Disk:

• Desktop computers
• Laptop computers
• TV and satellite recorders
• Servers and mainframes
• Portable (external) drives are sometimes used to backup home computers or transfer large files

Uses of USB Flash Disk:

• USB memory sticks — saving and transferring documents etc.
• They’re lightweight and small, so we can bring a thumb drive anywhere we go.

Uses of SD Card:

• SD and microSD memory cards are often used to record and store photos, music, videos, apps, and files. Both card types can store data taken directly from a device while users are on the go, such as photos or videos of a party, increasing their value because they allow users to store their memories as they occur. They are mostly used in smartphones to enhance their storage capacity.

Q.36: Describe application software.
Ans: Application Software:

Application Software is used to complete specific tasks, such as creating documents, databases, spreadsheets, and presentations. Computer games, media players, and web browsers are also examples of application software. Users need to install application software to accomplish specific tasks. Application software is not pre-installed on operating systems. They are installed separately. For example, making spreadsheets is not possible with Windows. For that, application software such as MS Excel is used. There are different types of application software.

(i) Productivity Software:
This kind of application software is used to produce things such as documents, spreadsheets, databases, and presentations. Many of the productivity software are intended to be used in businesses and offices. MS Office for Windows is an example of productivity software.

(ii) Business Software:
Business software are used to manage business activities efficiently. It is used to provide many business functions such as billing, database management, and inventory management.

(iii) Entertainment Software:
This type of software provides amusement and fulfills a user’s hobby. The most common entertainment software are video games.

(iv) Educational Software:
Educational software is used for teaching and learning. This kind of software is used in many schools to enhance the knowledge of students in learning different subjects.

GASEOUS EXCHANGE THEORY & QUESTION ANSWERS Chapter # 13

GASEOUS EXCHANGE

All living organisms require energy to perform various activities. They obtain energy by ATP. The continuous supply of ATP is made possible through respiration. Thus living organisms are always in need of gaseous exchange.

GASEOUS EXCHANGE IN PLANT:
Plants perform gaseous exchange during two processes.

• Photosynthesis
• Respiration

In plants, photosynthesis takes place during the day, where plants absorb CO₂ and release O₂. Respiration, however, takes place constantly, both day and night.

Gaseous Exchange in Unicellular Plants:
In unicellular and lower plants, gaseous exchange occurs through the cell membrane and moist body surface by diffusion.

Gaseous Exchange in Multi-cellular Plants:
In multicellular and higher plants, gaseous exchange occurs throughout the structure of leaves and stems. These plants have two types of respiratory structures:

• Stomata
• Lenticels

Gaseous Exchange through Stomata:
Stomata are microscopic pores located on both surfaces of leaves. Each stoma is surrounded by two bean-shaped cells called guard cells. Each guard cell has chloroplasts, with outer thinner and inner thicker walls. Guard cells control the opening and closing of stomata, allowing gaseous exchange to occur via diffusion.

Gaseous Exchange through Lenticels:
Woody stems have localized regions of loosely arranged cells with intercellular air spaces called lenticels. Through lenticels, respiratory gases can move freely in and out of the stem by diffusion.

Photorespiration:

Photorespiration is a process in which plants utilize oxygen and release carbon dioxide during daylight. Plants that perform photorespiration are biochemically classified as C₃ plants, examples of which include wheat, rice, maize, and sugarcane. 

MECHANISM:
During hot and dry days in summer, stomata are close in order to conserve water, and the rate of transpiration becomes reduced. The concentration of oxygen increases, then the carbon dioxide. In this condition, Ribulose biphosphate (RuBP) is combining with the oxygen instead of carbon dioxide in the presence of an enzyme ribulose biphosphate carboxylase / oxygenase or rubisco. It breaks into two compounds: phospho glyceric acid and phosphoglycolate.

$\text{RuBP} + \text{O}_2 \rightarrow \text{PGA} + \text{Phosphoglycolate}$

Phosphoglycolate is broken down to release $\text{CO}_2$.

$\text{Phosphoglycolate} \rightarrow \text{Serine} + \text{CO}_2$

Photorespiration is a useless process because there is no energy produced like in the process of respiration.

GASEOUS EXCHANGE IN ANIMALS:
Animals exchange gases during respiration. They take in oxygen and give out carbon dioxide constantly. Respiratory gases move across most respiratory surfaces by diffusion.

GASEOUS EXCHANGE IN HYDRA:
Hydra is a simple multicellular animal. It belongs to the Phylum Coelenterata. Hydra has a diploblastic body, i.e., the body consists of two cell layers.

• Ectoderm
• Endoderm

Respiratory organs are absent in hydra. It has aerobic respiration.

• Respiration Surface of Hydra:
  The ectoderm acts as the respiratory surface. The gaseous exchange in hydra takes place through this surface.

• Mechanism of Gaseous Exchange:
  In hydra, gaseous exchange takes place by diffusion. The ectoderm of hydra is permeable for oxygen and $\text{CO}_2$. During respiration, $\text{O}_2$ is diffused inside the body through ectoderm. Then $\text{CO}_2$ is also diffused throughout body cells by continuous diffusion. The resultant $\text{CO}_2$ exits out through ectoderm by diffusion.

GASEOUS EXCHANGE IN EARTHWORM:
The earthworm is a complex multicellular animal. It belongs to phylum Annelida. It has a cylindrical segmented body. The earthworm has aerobic respiration. The respiratory system is absent in the earthworm. The blood circulatory system of the earthworm helps in the transportation of gases in the body.

• Respiratory Surface of Earthworm:
  The outer skin of the earthworm acts as the respiratory surface. It is permeable and provides a greater surface area for respiration. The skin of the earthworm has goblet glands, which secrete mucus. Mucous keeps the skin moist. Beneath the skin, the network of blood vessels is also present.

Mechanism of Gaseous Exchange:
In earthworm, gaseous exchange takes place through moist skin. During respiration, $\text{O}_2$ enters by diffusion inside the body through skin. Blood absorbs the $\text{O}_2$ and transports it throughout body cells by circulation. The resultant $\text{CO}_2$ exits through skin by a similar procedure.

GASEOUS EXCHANGE IN COCKROACH:
Cockroach is a complex multicellular animal. It belongs to the Phylum Arthropoda. It has externally segmented body and jointed legs. Cockroach has aerobic respiration. It has evolved a special type of system which is termed as tracheal system.

Respiratory System of Cockroach:
The tracheal system of cockroach consists of two organs.

• Spiracles
• Trachea

Cockroach has an open-type blood circulatory system, but the blood of cockroach does not help in the transportation of gases because hemoglobin is absent in blood.

• Spiracles:
  They are small openings which are present on both lateral sides of the body. Cockroach has 10 pairs of spiracles. According to the position, they are divided into two types:

  • Thoracic spiracles

  • Abdominal spiracles

  • Thoracic Spiracles:
    Those spiracles which are present at the thorax region are called thoracic spiracles. There are two pairs in number. Thoracic spiracles are present at the junction of thoracic segments. They have outward opening valves and help in expiration.

  • Abdominal Spiracles:
    Those spiracles which are present at the abdominal region are called abdominal spiracles. There are 8 pairs in number and are present at the 8 segments of the abdomen. They have inward opening valves and help in inspiration.

• Trachea:
  Trachea are tube-like structures in which spiracles are open. The wall of the trachea is composed of a single layer of epithelial cells. The wall also contains cartilaginous rings. The fine branches of trachea, called tracheoles, are filled with a fluid called tracheal fluid. Tracheoles are present near cells or tissues, and they are blind from the anterior end.

Mechanism of Gaseous Exchange:
The mechanism of gaseous exchange in cockroach is completed in two continuous steps.

• Inspiration
• Expiration

• Inspiration:
  The rushing of air inside the body is called inspiration. In cockroach, during inspiration, air enters through abdominal spiracles and finally reaches into tracheoles by trachea. Air is dissolved in tracheal fluid; then $\text{O}_2$ of air is diffused inside the cell by diffusion.

• Expiration:

        The outward movement of air from the body is called expiration. During expiration, the resultant  

${\text{ CO}}_2$CO2​ is diffused in air from cells by diffusion. By inward movement of sternum and tergum,            pressure is exerted on the trachea, and air is expelled out through thoracic spiracles.

GASEOUS EXCHANGE IN FISH:
Respirator organs in fish and other aquatic animals are gills.

• Structure of Gills:
  They are formed as an outgrowth of the pharynx and lie within the body. Each gill is a highly vascularized structure consisting of two rows of hundreds of filaments, which are arranged in a V-shape, supported by the cartilage called gill arc or gill bar. Each filament is folded into numerous plate-like structures called lamellae that give the gills a greater surface area and are provided with a network of blood capillaries. Each gill is covered by an operculum, and the cover either opens through gill slits.

• Mechanism of Gaseous Exchange:
  Water enters into the mouth, passes over the gill through the pharynx, and exits back through the opercula. Since the concentration of oxygen in water is low and water is denser than air, fish must use considerable energy to ventilate its gills.

• Counter Current Flow:
  Gaseous exchange in gills is also facilitated due to the counter-current flow of water and blood. The blood flows in a direction opposite to the movement of water in capillaries of lamellae across the gills. Thus, the most highly oxygenated blood is brought close to the water, just entering the gills, and that has even higher oxygen content than the blood. As the water flows over the lamellae, it gradually loses its oxygen to the blood; it encounters the blood, i.e., also increasingly in oxygen. In this way, the gradient encouraging oxygen to move from water into the blood is maintained across the lamellae. Counter-current flow of water is effective as it enables the fish to extract up to 80% - 90% of oxygen from the water that flows over the gills.

GASEOUS EXCHANGE IN FROG:
The frog is a complex multicellular animal. It belongs to phylum Chordate. Frog belongs to class Amphibia because it is found in both water and land. The frog has aerobic respiration. It has three types of respiration:

• Cutaneous respiration
• Buccal respiration
• Pulmonary respiration

• Cutaneous Respiration:
  Respiration takes place through the skin, called cutaneous respiration. This type of respiration is found in frogs when they are present inside the mud during the hibernation season.

• Buccal Respiration:
  Respiration takes place through the buccal cavity, called buccal respiration. This type of respiration is found in frogs when they are in water.

• Pulmonary Respiration:
  Respiration takes place through the lungs, called pulmonary respiration. This type of respiration is found in frogs when they are on land.

Pulmonary Respiratory System of Frog:
The pulmonary respiratory system of frogs consists of the following organs:

• Nostrils

• Bucco-pharyngeal Cavity

• Glottis

• Larynx

• Bronchus

• Lungs

• Nostrils:
  They are small openings. There are two pairs in number. One pair is present outside, while the other pair is present inside. Nostrils help as a passage of air.

• Bucco-pharyngeal Cavity:
  Buccal cavity and Pharynx are collectively called the bucco-pharyngeal cavity. The floor of this cavity is movable. It also helps as a passage of air.

• Glottis:
  It is a small opening. The respiratory system and digestive system are separated through the glottis. The opening of the glottis is guarded by a flap called the epiglottis.

• Larynx:
  It is a chamber-like structure. It is also known as the voice box. The walls of the larynx are composed of cartilage.

• Bronchus:
  They are hollow tube-like structures that open into the lungs. The passage of air takes place through the bronchus.

• Lungs:
  The lungs are balloon-shaped structures. A single pair of lungs is present. Lungs have a pinkish-reddish color. The outer surface of the lungs is smooth, while the inner surface is folded. Both the lungs are composed of thin-walled small chambers called alveoli or air sacs. At the upper surface of alveoli, blood capillaries are present. Alveoli help in the exchange of gases.

Mechanism of Gaseous Exchange:
During inspiration, air enters through nostrils into the bucco-pharyngeal cavity. At that time, the glottis is closed. Due to the air, the floor of the bucco-pharyngeal cavity moves downward. After that, the nostril is closed, and the glottis is open. Then the floor of the bucco-pharyngeal cavity moves upward, due to which air rushes into the lungs. Inside the lungs, $\text{O}_2$ is absorbed in the blood, and $\text{CO}_2$ comes out of the lungs from the blood. Due to the contraction of the lungs, air is expelled out with $\text{CO}_2$. Frogs have incomplete ventilation because lungs are not completely empty with air.

GASEOUS EXCHANGE IN BIRDS:
Birds are complex multicellular animals. They belong to Phylum Chordata. Birds have aerobic respiration. They have complete ventilation. The ventilation of air takes place in a unidirectional manner. Birds have evolved the most efficient respiratory system.

Respiratory System of Birds:
Birds have developed a complex respiratory system. The respiratory system consists of two organs.

• Lungs:
  Lungs are balloon-shaped structures. A pair of lungs is present inside the abdominal cavity at both sides of the vertebral column.

  Lungs are muscularized and vascularized structures because they consist of muscles and a large number of blood vessels. The outer surface of the lungs is smooth, while the inner surface is divided into numerous small, highly vascularized, thin membranous channels known as parabronchi.

• Air Sacs:
  Birds have 8–9 non-vascularized structures called air sacs. Air sacs are present around the lungs, and they also connect with parabronchi. Some air sacs are also found inside the bone.

Mechanism of Gaseous Exchange:
Birds have complete ventilation or unidirectional flow of air. During exchange, birds first inspire air; inspiratic air passes through lungs and stores inside air sacs, then birds perform second inspiration. In the second inspiration, air pushes the first inspiratic air into the lungs, where gaseous exchange takes place through parabronchi. After expired air is removed, the one-way flow of air enables a bird to fly at very high altitudes without any storage of oxygen.

GASEOUS EXCHANGE IN MAN:
Man is a complex multicellular and social living organism. It belongs to Phylum Chordata. Man has developed a complex respiratory system that helps in gaseous exchange. It has aerobic respiration. Man has complete ventilation in two directions.

Respiratory System of Man:
Man has developed a complex respiratory system. The respiratory system of man consists of nine organs.

• External Nares or Nostrils

• Nasal Cavity

• Internal Nares

• Pharynx

• Glottis and Epiglottis

• Larynx

• Trachea

• Bronchus

• Lungs

• External Nares or Nostrils:
  These are small openings present at the terminal part of the face just above the mouth and are one pair in number. The wall of external nares is composed of elastic cartilage.

  • Function:
    During inspiration and expiration, the passage of air takes place through external nares.

• Nasal Cavity:
  Each external nare opens behind into a cavity called the nasal cavity. The nasal cavity and buccal cavity are separated by a plate called the palate. The wall of the nasal cavity is also composed of elastic cartilage. The inner wall is lined with ciliated epithelial cells, which secrete mucus. Inside the nasal cavity, small hairs are also present.

  • Function:
    The mucus of the nasal cavity keeps the nose moist. Small hairs filter the air of germs and dust particles. The nasal cavity also helps in the passage of air during inspiration and expiration.

• Internal Nares:
  These are one pair of small openings present just above the junction of the buccal cavity and pharynx. The wall of internal nares is composed of elastic cartilage.

  • Function:
    Passage of air takes place during inspiration and expiration through internal nares.

• Pharynx:
  It is a small tubular structure with muscular walls. The buccal cavity and nasal cavity both open into it. The pharynx is present inside the neck region.

• Function:
  The pharynx performs two functions:
• Passage of air during respiration
• Passage of food during digestion

• Glottis and Epiglottis:
  Glottis is a small opening present in the wall of the pharynx. The respiratory and digestive tracts are separated through the glottis. The opening of the glottis is guarded by a flap called the epiglottis. Movement of the epiglottis is involuntary.

  • Function:
    Passage of air takes place through the glottis.

• Larynx:
  It is a small chamber-like structure. The larynx is also present inside the neck. The wall of the larynx is composed of cartilage. The larynx is also known as the sound box. Inside the larynx, one pair of cartilaginous structures is present, called vocal cords.

  • Function:
    The larynx performs two functions:
    • Passage of air takes place through the larynx.
    • It helps in producing sound through vocal cords.

• Trachea:
  The trachea is a long, straight tube-like structure. It is also known as the windpipe. The trachea is present inside the chest cavity. The wall of the trachea is composed of ciliated epithelial cells. The wall also contains C-shaped cartilaginous rings that prevent it from collapsing during air drawing. The wall of the trachea also contains goblet cells that secrete mucus. Mucus keeps the wall of the trachea moist.

  • Function:
    Passage of air takes place during inspiration and expiration.

• Bronchus:
  Near the lungs, the trachea is divided into two branches; each branch is known as a bronchus. Each bronchus enters into the lungs and divides into fine and small branches called bronchioles. The walls of the bronchi and bronchioles are composed of ciliated epithelial cells.

  • Function:
    Passage of air takes place during inspiration and expiration through the bronchi.

• Lungs:
  Lungs are the main respiratory organs. They help in gas exchange.

• Shape:
  Man has sac-like or balloon-shaped lungs.

• Number:
  Man has one pair of lungs.

• Colour:
  Both lungs have a pinkish-red colour. This colour appears due to the presence of blood capillaries on the lungs.

• Location:
  Lungs are located inside the thoracic or chest cavity.

• Protection:
  Both lungs are protected inside the bony cage. The bony cage is produced by the sternum bone at the ventral surface, ribs at both lateral surfaces, and the vertebral column at the dorsal surface. At the lower surface, both lungs are supported by the diaphragm.

• Covering:
  Both lungs are covered by a double-layered membrane called the pleural membrane. Between both layers, a fluid is present called pleural fluid. Pleural fluid develops pressure called pleural pressure, which helps in inspiration and expiration. Pleural fluid also keeps the lungs moist.

MORPHOLOGY OF LUNGS:
Externally, lungs have a smooth surface. Lungs have a large number of blood capillaries on their surface. Externally, lungs are divided into lobes. The right lung consists of three lobes, while the left lung consists of two lobes.

Anatomy of Lungs:
Internally, lungs are folded in structure; they are spongy in nature. Lungs are muscularized and vascularized structures. Each lung consists of small sac-like structures called air sacs or alveoli.

Structure of Alveoli:
Alveoli are small sac-like structures; both lungs contain 700 million alveoli. The wall of the alveoli is composed of a thin layer of epithelial cells. Each alveolus has a branch of bronchiole. On the surface of the alveoli, a network of blood capillaries is also present, which helps in gaseous exchange.

Function of Lungs:
Lungs help in gaseous exchange between alveoli and blood.

• Mechanism of Gaseous Exchange:
  During inspiration, air enters inside the lungs. The oxygen of air is absorbed in the blood, which is present on the alveoli surface through diffusion. Absorption of oxygen takes place by the binding of Hemoglobin with oxygen. Similarly, carbon dioxide is released into the air of alveoli from blood by diffusion.

• Mechanism of Breathing:
  The process of breathing takes place as a result of two continuous processes.

  • Inspiration (Inhalation)

  • Expiration (Exhalation)

  • Inspiration (Inhalation):
    "The process in which air enters into the lungs from the environment through the respiratory tract called inspiration."

    Mechanism:
    During inspiration, the outer layer of intercostals and diaphragm muscles both contract, due to which ribs move in an upward direction while at the same time, the diaphragm moves in a downward direction. An area is produced inside the chest cavity to expand the lungs during inspiration. At the same time, pleural pressure is reduced on the lungs. Air enters inside the lungs through the respiratory tract, and the process of inspiration takes place.

  • Expiration (Exhalation):
    "The movement of air from lungs to the environment called expiration."

    Mechanism:
    Expiration is the process opposite to inspiration. During expiration, the inner layer of intercostal muscles contract, and diaphragm muscles are relaxed. Due to this, ribs move in an inward direction, and the diaphragm moves in an upward direction. At the same time, pleural pressure is increased on the lungs, resulting in air being expelled into the environment, and expiration takes place.

• Rate of Breathing:
  The process of breathing is voluntary and involuntary. Deep breathing, slow breathing, and the stoppage of breathing is under voluntary control, while continuous breathing is involuntary control. The rate of breathing is influenced by the concentration of CO₂ and H₄ in the blood. Concentration of CO₂ and H⁴ is controlled by Carotid and Aortic bodies, which are present in carotid and aortic arteries. The whole process is controlled by the last part of the brain called Medulla Oblongata.

• Lung Capacity:
  Both the lungs of man have a 5-liter air capacity, equivalent to 5000 cm³. There are three types of air volume found in human lungs.

• Tidal Volume:
  During normal breathing, air occupies 10% of total capacity, which is equal to 450-500 cm³. This capacity of the lung is called tidal volume.

• Vital Volume:
  During deep breathing, air enters the lungs and occupies a 4-liter capacity of the lungs. This capacity of the lungs is called vital volume.

• Residual Volume:
  The remaining one liter of air is already present inside the lungs. This capacity of the lungs is called residual volume. Residual volume prevents the lungs from collapsing during expiration.

RESPIRATORY TRACT DISORDERS:

• Tuberculosis (T.B):
  It is an infectious disease caused by a bacterium, Mycobacterium tuberculosis. It is a contagious disease that is transferred from one person to another by coughing, sneezing, or by using patient personal things. It is common in unhygienic areas. Its main symptoms are prolonged coughing, fever, loss of weight, loss of appetite, chest pain, difficulty in breathing, and spitting with blood.

• Asthma (Deficiency in Breathing):
  It is a serious respiratory tract disorder. It is simply called an attack of breathlessness. It is characterized by wheezing when breathing out. It may be due to allergic reactions because of pollen grain, dust, or fur. In some conditions, it may be hereditary. Serious attacks of asthma may lead to fatal consequences.

• Lung Cancer (Abnormal Cell Division):
  It is a condition of rapid division of cells.

  • Cause: Smoking (active or passive)
  • Toxics: Nicotine, SO₂, etc.
  • Damage: Due to the damage of cilia of epithelial cells of the respiratory tract.
  • Effect: Dust and germs settle down inside the lungs.
  • Abnormality: Abnormal nuclei are developed and penetrate other tissues (disturbing normal cell division and causing cancer).

• Emphysema (Burst Alveoli):
  It is the condition of enlargement of alveoli of lungs.

  • Cause: NO₂, SO₂, CO inhaled by air.
  • Damage: Elasticity of lungs decreases.
  • Abnormality: Alveoli are ruptured and lungs become harder.
  • Symptoms: Supply of oxygen to brain and tissues disturbed, problem in breathing, sluggishness.

TRANSPORT OF GASSES:
During respiration, transportation of oxygen and carbon dioxide takes place. The transportation of O₂ and CO₂ takes place by means of a fluid called blood. So blood is the vehicle for the transportation of gases.

• Transportation Of Oxygen:

  • Role of Hemoglobin:
    Hemoglobin is an iron-containing protein found in the blood. Each hemoglobin has four molecules of iron, known as Heme part. Hemoglobin has a tendency to combine with oxygen at the surface of the lung. Oxygen of air is bound with the Hemoglobin of blood and produces an unstable compound called oxyhemoglobin.

    $$Hb + 4O_2 \rightarrow Hb (O_2)_4$$

    This unstable compound is transported towards the cells and tissues through blood circulation. Near the cells and tissues, oxyhemoglobin dissociates, and oxygen and Hemoglobin are separated. Then oxygen is diffused inside the cell by diffusion. Inside the cell, oxidation of food takes place as a result of which CO₂, H₂O, and energy are produced.

  • Role of Myoglobin:
    Myoglobin is also an iron-containing protein found in the muscles. They are smaller than Hemoglobin. Myoglobin tightly binds with oxygen, due to which the red color of muscles appears.

• Transportation Of Carbon Dioxide:
  Carbon dioxide is a respiratory by-product produced as a result of the oxidation of food in tissues to the lungs. All the CO₂ produced in body tissues reaches the lungs by three means.

• Transportation Of 35% CO₂:
  35% CO₂ is transported through Hemoglobin of blood. It combines with the amino group of Hemoglobin and produces an unstable compound called Carbaminohemoglobin. At the surface of the lung, this compound dissociates into Hemoglobin and CO₂. So in this way, 35% CO₂ reaches the lungs from tissue.

• Transportation Of 60% CO₂:
  60% CO₂ reaches the lungs through water of R.B.C. The following reactions take place during the transportation of this CO₂.

  $$CO₂ + H₂O(R.B.C) \leftrightarrow H₂CO₃$$ $$H₂CO₃ \leftrightarrow H⁺ + HCO₃⁻$$ $$K⁺ + HCO₃⁻ \leftrightarrow KHCO₃$$

• Transportation Of 5% CO₂:
  The remaining 5% CO₂ is transported through the water of plasma. The following reactions take place during the transportation of this CO₂.

  $$CO₂ + H₂O(plasma) \leftrightarrow H₂CO₃$$ $$H₂CO₃ \leftrightarrow H⁺ + HCO₃⁻$$ $$Na⁺ + HCO₃⁻ \leftrightarrow NaHCO₃$$

These all reactions take place in the presence of various enzymes such as Carbonic anhydrase present in Red Blood Cells.