Microsoft Word - CS XI 2015 PDF.docx

[Virtual Presenter] CHAPTER SIX CHAPTER SIX CHAPTER SIX CHAPTER SIX 6 SOFTWARE SOFTWARE SOFTWARE SOFTWARE OBJECTIVE: When you have completed this chapter, you will be able to know about the Short Answer Questions Q1. Define software. What are the two main categories of software? Q2. Define operating system. What are the famous Operating Systems used now a days? Q3. Define operating Systems. What are the key functions of an operating system? Q4. Write a short note on Microsoft Disk Operating System. Q5. Write a short note on Microsoft Windows Operating System. Q6. Write a short note on UNIX Operating System. Q7. Define user interface. How many types of operating systems are there regarding user interface? Q8. What do you know about boot up process? Q9. Define computer language. Why computer languages are used? Give example. Q10. Name the different generations of programming languages. Q11. Define Language Translators. How many types of language translators are there? Long Answer Questions Q1. Define Software. What are the major types of software? Mention software examples. Q2. Explain Operating Systems. What are the key functions of an operating system? Q3. Define Language Translators. How many types of language translators are there? Explain. Q4. What are operating system types? Explain in detail. Q5. Explain different generations of programming languages. Page 43 of 157 VER: 04.

[Audio] CHAPTER # 6 SOFTWARE ===========Short Questions and Answers========= Q1. Define software. What are the two main categories of software? Software Set of information stored as interconnected programs to perform a specific task is called Software. OR The instruction set that tell the computer what to do is called software. OR Set of instruction that perform particular task is called software. The following are the two major types.  System Software System Software is a set of programs which is designed by the manufacture of computer. These programs are developed for efficient management of hardware. They improve the functional capabilities of the computer and assist the user to solve their problems easily. Operating systems, antivirus, disk managers etc are the examples of system software.  Application Software Application Software is a collection of programs which are written by the users themselves to solve their problem. These programs are written in computer language such as FORTRAN, Basic, C Language and Pascal. MsWord, Ms-Power Point are the examples of application software. Q2. Define operating system. What are the famous Operating Systems used now a days? An Operating system is a master control program of a computer system which manages the overall performance of the computer system. A number of operating systems have been introduced by world famous software companies. Example The following are the operating systems which are being used worldwide. MS-DOS MS-Windows Red Hat-Linux Novel Netware Unix Q3. Define operating Systems. What are the key functions of an operating system? Operating System An operating system consists of master programs that manage the basic computer operations and resources. Explanation An operating system is system software. It contains a number of programs to manage system resources. A user cannot communicate to the microprocessor of computer system until an operating system is not installed. Windows XP, DOS, Linux, Unix are the examples of famous operating systems used today. Page 44 of 157 VER: 04.

[Audio] Operating System Functions An Operating system performs a number of functions. The major functions of an operating system are as follows:  Booting the Computer System  Managing Storage Media   Providing User Interface  Managing Files   Managing Computer Resources Q4. Write a short note on Microsoft Disk Operating System. DOS (Disk Operating System) is a command line operating system of the famous software company Microsoft. Explanation DOS has been a prominent and dominating operating system during 1980s and early 1990s. It is a single user, single tasking operating system used for micro computers. IBM's disk operating system is called PC-DOS. MS-DOS Commands DOS has a number of commands which are executed by typing at command prompt. The following are some basic commands. COMMANDS PURPOSE CLS To clear the screen. COPY To copy a file. DEL To delete a file. DISKCOPY To copy all files from one disk to another. MS-DOS was introduced by Microsoft and PC-DOS was introduced by IBM. MS-DOS is still being used for the administration of Local Area Networks. Q5. Write a short note on Microsoft Windows Operating System. MS-Windows is a GUI based multi-tasking operating system launched by Microsoft. Explanation Windows operating system was developed by Microsoft Corporation in 1985. It has a graphical user interface. In 1990 Microsoft introduced windows 3.0 as an improved version of previous windows. In 1995 Microsoft introduced Windows 95 with more features and enhanced capabilities. Advanced Versions of Windows Microsoft has evolved windows with more advancement with the passage of time. Windows 95 Windows NT ( Client and Server) Windows 2000 ( Client and Server) Windows 2003 (Client and Server) Q6. Write a short note on UNIX Operating System. UNIX operating system was first developed by Bell laboratories, USA in 1969. Page 45 of 157 VER: 04.

[Audio] Explanation UNIX was developed for the mini and micro computers. UNIX has a number of impressive features. It is a complete multi-tasking, multi-user, time sharing operating system written in mostly in C-language. It is also considered a better operating system for main frame computers. Q7. Define user interface. How many types of operating systems are there regarding user interface? An operating system user interface provides environment for the user to communicate with the computer system. Types of User Interfaces There are two major types of user interfaces provided by different operating systems.  Command Line Interface A command line interface is a text based user interface. User has to type the commands on command prompt. In this interface user has to memorize commands. DOS is an example of command line operating system.  Graphical User Interface Graphical user interface provides a window like and menu like environment as user interface. Unlike the command line interface there is no need to type command. Commands can be given by selecting different options from the GUI environment. Commands can be given not only using keyboard but also using pointing devices. Windows is an example of GUI environment. Q8. What do you know about boot up process? Definition The term booting refers to loading of operating system from secondary storage to main memory. Boating is done through a program called bootstrap loader. Boot-up process is performed on every startup of computer system. Explanation In computing, booting (also known as booting up) is a bootstrapping process that starts operating systems when the user turns on a computer system. A boot sequence is the initial set of operations that the computer performs when power is switched on. The boot loader typically loads the main operating system for the computer. A successful boot is dependent on 3 conditions - the hardware, BIOS and operating system files to function without errors. When an error occurs, you will be notified by error messages, beeping sounds or in the worst scenario, a blank screen. The boot up process is a list of detailed procedures that the system undergoes to perform all system checks and load all necessary files to bring the computer to an operable state. The Windows XP boot up process comprises of the following procedures. Q9. Define computer language. Why computer languages are used? Give example. A computer language is a programming tool to develop programs. A computer language provides instructions for coding program modules. Integrated programs develop an application or system software. Page 46 of 157 VER: 04.

[Audio] Explanation In order to facilitate the user, the computer programmer needs to develop software. For this purpose it necessary to have some programming tool. So the computer language is used to develop software. Example C, C++, Java, C#, VB are some examples of famous computer languages. Q10. Name the different generations of programming languages. Programming languages have been classified into several programming language generations. Historically, this classification was used to indicate increasing power of programming styles. Later writers have somewhat redefined the meanings as distinctions previously seen as important became less significant to current practice.  First Generation: -- Machine language  Second Generation: -- Assembly language   Third generation: -- High level language  Fourth generation: -- Very high level language   Fifth generation: -- Natural language Q11. Define Language Translators. How many types of language translators are there? Language Translators A program which translates the source code into machine language is called language translator. Example C-Language Compiler Visual Basic Interpreter Types of Language Translators There are mainly two types of language translators. These are as follows: Compiler A compiler is a language translator which translates all the program instructions at once and gives output. Example C-Language Compiler CPP Compiler Interpreter An interpreter is a language translator which translates the programs instructions line by line.  Example Visual Basic Interpreter Java Interpreter ===========Long Questions and Answers========= Q1. Define Software. What are the major types of software? Mention software examples. Software Software is a collection of integrated programs, which are installed on computer system and used for different purposes. Page 47 of 157 VER: 04.

[Audio] Explanation Computer software is defined as a set of programs and procedures that are intended to perform some tasks on a computer system. A software program is a set of instructions that are aimed at changing the state of computer hardware. At the lowest level software is in a form of an assembly language, a set of instructions in a machine-understandable form. At the highest level, software is in a form of high-level languages, which are compiled or interpreted into machine language code. Software is the logical components of computer system stored on storage media. These are developed using some computer languages. Software is used not only to control the computer system but also to perform the task required by the user. Examples Ms-Word ( A word processor ) Windows XP ( An Operating System ) Internet Explorer ( A Web Browser ) Norton Antivirus ( An Antivirus ) Software Application System Software Software User written Ready Made Language Operating Software Software Software Software Types of Software Software are divided into two main categories. These are as follows: 1-System Software The system software is defined as software which controls, manages, protects or directly related to the hardware. Explanation System software is computer software designed to operate the computer hardware and to provide a platform for.

[Audio] Explanation Application software, also known as an application has been designed to help the user to perform singular or multiple related specific tasks. Examples include enterprise software, accounting software, office suites, graphics software and media players. Many application programs deal principally with documents. Apps may be bundled with the computer and its system software, or may be published separately. Some users are satisfied with the bundled apps and need never install one. Application software is developed to solve user problems. A user problem may be any general, business, scientific or technical problem. Example Corel Draw (A Graphics Designing Software) Peach Tree (An Accounting Software) Auto CAD (Civil Engineering Designing Software) Mozilla Firefox (A Web Browser) Types of Application Software The following are some types of application software.  Word Processing Software This software enables the users to create and edit documents. The most popular examples of this type of software are MS-Word, WordPad, Notepad and some other text editors.  Database Software Database is a structured collection of data. A computer database relies on database software to organize the data and enable the database users to achieve database operations. Database software allows the users to store and retrieve data from databases. Examples are Oracle, MS-Access, etc.  Spreadsheet Software Excel, Lotus 1-2-3 and Apple Numbers are some examples of spreadsheet software. Spreadsheet software allows users to perform calculations. They simulate paper worksheets by displaying multiple cells that make up a grid.  Multimedia Software They allow the users to create and play audio and video media. They are capable of playing media files. Audio converters, players, burners, video encoders and decoders are some forms of multimedia software. Examples of this type of software include Real Player and Media Player.  Presentation Software The software that is used to display information in the form of a slide show is known as presentation software. This type of software includes three functions, namely, editing that allows insertion and formatting of text, methods to include graphics in the text and a functionality of executing the slide shows. Microsoft PowerPoint is the best example of presentation software. Q2. Explain Operating Systems. What are the key functions of an operating system? Operating System An operating system consists of master programs that manage the basic computer operations and resources. Page 49 of 157 VER: 04.

[Audio] Explanation An operating system is system software. It contains a number of programs to manage system resources. A user cannot communicate to the microprocessor of computer system until an operating system is not installed. An operating system improves the performance and efficiency of a computer system. An operating system (OS) is software, consisting of programs and data, that runs on computers, manages computer hardware resources, and provides common services for execution of various application software. The operating system is the most important type of system software in a computer system. Without an operating system, a user cannot run an application program on their computer, unless the application program is self booting. Example Windows XP DOS Linux Unix Operating System Functions An Operating system performs a number of functions. The major functions of an operating system are as follows:  Booting the Computer System The term booting refers to loading of operating system from secondary storage to main memory. Boating is done through a program called bootstrap loader. Boot-up process is performed on every startup of computer system.  Managing Storage Media Storage devices like hard disks, CDs, floppy disks and other storage devices are formatted, initialized or prepared to read and write data by operating system. The file system on storage media is also managed by operating system.  Providing User Interface An Operating system provides a user interface to communicate user instructions to computer system. A user interface includes on-screen facilities for communication. A user interface may be a command like interface (CLI) like DOS and graphical user interface (GUI) like windows.  Managing Files An operating system provides commands to create and manage files on disks. The file operations like COPY, PASTE, DELETE, BACKUP, RENAME and etc are performed through operating system.  Managing Computer Resources An operating system manages all type of resources like CPU, Input and Output devices, memory units and all the peripheral devices connected to the computer system. Q3. Define Language Translators. How many types of language translators are there? Explain. Language Translators A program which translates the source code into machine language is called language translator. Page 50 of 157 VER: 04.

[Audio] Explanation In order to develop software, a programmer writes instructions in any computer language. The language code written by the programmer is called source code. It needs to be translated so that it can be understood by the CPU and this task is done by a program which is known as language translator. Example C-Language Compiler Visual Basic Interpreter Types of Language Translators There are mainly two types of language translators. These are as follows: Compiler A compiler is a language translator which translates all the program instructions at once and gives output. Explanation Some languages use the compiler to translate the source code program into machine language. The computer translates all the instructions at once and until and unless it does not print the result if there is no error found. Example C-Language Compiler CPP Compiler Interpreter An interpreter is a language translator which translates the programs instructions line by line.  Explanation Some languages use interpreter to translate the source code program into machine language. The interpreter translates the instructions one after another as these are written in the program. An instruction is executed if it does not contain any error and an instruction is not executed if it contains error.  Example Visual Basic Interpreter Java Interpreter Q4. What are operating system types? Explain in detail. (Each type can be asked as a short question) The operating systems contribute to the simplification of the human interaction with the computer hardware. They are responsible for linking application programs with the hardware, thus achieving an easy user access to the computers. An operating system consists of master programs that manage the basic computer operations and resources. The following are the major kinds of operating system. Real-time Operating System It is a multitasking operating system that aims at executing real-time applications. Real-time operating systems often use specialized scheduling algorithms so that they can achieve a deterministic nature of behavior. The main object of real-time operating systems is their quick and predictable response to events. They either have an event-driven or a time-sharing design. An event-driven system switches between tasks based of their priorities while time-sharing operating systems switch tasks based on clock interrupts. Page 51 of 157 VER: 04.

[Audio] Multi-user and Single-user Operating Systems The operating systems of this type allow a multiple users to access a computer system concurrently. Time-sharing system can be classified as multi-user systems as they enable a multiple user access to a computer through the sharing of time. Single-user operating systems, as opposed to a multi-user operating system, are usable by a single user at a time. Being able to have multiple accounts on a Windows operating system does not make it a multi-user system. Rather, only the network administrator is the real user. But for a Unix-like operating system, it is possible for two users to login at a time and this capability of the OS makes it a multi-user operating system. Multi-tasking and Single-tasking Operating Systems When a single program is allowed to run at a time, the system is grouped under a single-tasking system, while in case the operating system allows the execution of multiple tasks at one time, it is classified as a multitasking operating system. Multi-tasking can be of two types namely, preemptive or co-operative. In pre-emptive multitasking, the operating system slices the CPU time and dedicates one slot to each of the programs. Unix-like operating systems such as Solaris and Linux support pre-emptive multitasking. If you are aware of the multi-threading terminology, you can consider this type of multi-tasking as similar to interleaved multi-threading. Cooperative multitasking is achieved by relying on each process to give time to the other processes in a defined manner. This kind og multi-tasking is similar to the idea of block multithreading in which one thread runs till it is blocked by some other event. MS Windows prior to Windows 95 used to support cooperative multitasking. Distributed Operating System An operating system that manages a group of independent computers and makes them appear to be a single computer is known as a distributed operating system. The development of networked computers that could be linked and communicate with each other, gave rise to distributed computing. Distributed computations are carried out on more than one machine. When computers in a group work in cooperation, they make a distributed system. Embedded System The operating systems designed for being used in embedded computer systems are known as embedded operating systems. They are designed to operate on small machines like PDAs with less autonomy. They are able to operate with a limited number of resources. They are very compact and extremely efficient by design. Windows CE, FreeBSD and Minix 3 are some examples of embedded operating systems. Q5. Explain different generations of programming languages. Programming languages have been classified into several programming language generations. Historically, this classification was used to indicate increasing power of programming styles. Later writers have somewhat redefined the meanings as distinctions previously seen as important became less significant to current practice.  First Generation: -- Machine language   Second Generation: -- Assembly language  Third generation: -- High level language Page 52 of 157 VER: 04.

[Audio]  Fourth generation: -- Very high level language  Fifth generation: -- Natural language  1. First Generation: Machine Language A first-generation programming language is a machine-level programming language. It consists of 1s and 0s. Originally, no translator was used to compile or assemble the firstgeneration language. The first-generation programming instructions were entered through the front panel switches of the computer system. The main benefit of programming in a first-generation programming language is that the code a user writes can run very fast and efficiently, since it is directly executed by the CPU. However, machine language is somewhat more difficult to learn than higher generational programming languages, and it is far more difficult to edit if errors occur. 2. Second Generation: Assembly Language Assembly Language is also Known as second generation language. Assembly language is the low level languages. Assembly language is less complex to use than a machine language. Assembly language uses English word and symbols as abbreviation code to replace the 0s and 1s of machine language (A for "add" C for "compare", and MP for "Multiply"). A translator is required to convert the assembly language program into machine language that can executed by the computer. This translating program is called assembler. The assembler converted the assembly language into machine language. 3. Third generation: -- High level language High level language is also known as third generation high level language. There languages use English text and mathematical formulas. The essential feature of third generation language is machine independence, meaning that the language can be used on different computers with little or change in performance or functionality. High level language is also knows as problem oriented language because the programming instructions are especially picked to be useful for solving particular type of problem. A language translator is required to convert a high level language program into machine language. Most common high level programming languages are: (BASIC, C-Language, COBOL, Pascal, and FORTRAN) 4. Fourth generation: -- Very high level language Fourth generation language is a programming language designed with a specific purpose in mind, such as the development of commercial business software. These programming language are more powerful and specialized than existing high level language. Third generation language development method can be slow and error prone. All fourth generation language designed to reduce programming effort. Most common high level programming languages are: (FoxPro, C++, C#, JAVA and SQL (Structure Query Language). 5. Fifth generation: Natural Language Fifth generation language is also called natural language. The natural language is similar to human language. These languages are designed to make the computer "smarter". Natural languages are part of the field of study known as artificial intelligence. Artificial intelligence (AI) is a group of related technologies that attempt to develop machine to emulate human-like qualities, such as learning, reasoning, communicating, seeing, and hearing. Page 53 of 157 VER: 04.

[Audio] CHAPTER SEVEN CHAPTER SEVEN CHAPTER SEVEN CHAPTER SEVEN 7 COMPUTER COMPUTER COMPUTER COMPUTER ARCHITECTURE ARCHITECTURE ARCHITECTURE ARCHITECTURE OBJECTIVE: When you have completed this chapter, you will be able to know about the Short Answer Questions Q1. What are the major components of digital computers? Q2. Define registers. Write names for various registers of CPU. Q3. Define instruction cycle. Q4. Define Bus. How many types of buses are there? Explain in detail. Long Answer Questions Q1. Describe the major components of digital computers? Q2. Define registers? Explain various registers of CPU. Q3. Define Bus. How many types of buses are there? Explain in detail. Q4. Describe fetch cycle or execute cycle inside the CPU. Q5. Describe the procedure of execution of an instruction with diagram. Page 54 of 157 VER: 04.

[Audio] CHAPTER # 7 COMPUTER ARCHITECTURE ===========Long Questions and Answers========= Q1. What are the major components of digital computers? The computer system is a complex computing device. It involves some major components for the processing of data. There are the primary components and without these components the processing cycle cannot be completed. Components Of Digital Computer: The following are the components of a digital computer: Input Unit Output Unit Central Processing Unit Memory Unit Q2. Define registers. Write names for various registers of CPU. Registers Registers are the temporary storage device which holds data and instructions until it is being processed or manipulated. Explanation Each register within the CPU performs a specific role. The registers help in the processing of data. The register's size and operations that take place in the register reflects the specific function that the register performs in the computer. Types of Registers Following are some types of registers: General Purpose Registers Accumulator Status Registers Memory Buffer Registers Memory Address Registers Instruction Registers Program Counter Stack Pointer Q3. Define instruction cycle. Instruction Cycle The processing required for a single instruction is called Instruction cycle. Here instruction cycle has been represented with diagram. It involves the following two steps.  Fetch Cycle The fetch cycle is that duration of time in which an instruction stored in the memory is brought to an appropriate register. All this happens under the commands from control unit of the CPU. The process of bringing an instruction from memory to a register is called a fetch cycle. It has to be completed in specified duration of time. Page 55 of 157 VER: 04.

[Audio]  Execute Cycle The process of execution of an instruction by the CPU in a specified interval of time is called execute cycle. The instruction fetched from memory is placed in a register where it is decoded and executed by ALU in the execute cycle. The CPU when fetching an instruction is set to be in fetch stage and while executing an instruction is in execute stage. These two stages appear alternately. Q4. Define Bus. How many types of buses are there? Explain in detail. A bus is defined as the physical pathway for transmission of data and instructions in the central processing unit. Types of Buses The following are three types of buses: Address Buses The address bus is used by the microprocessor to transmit the address of the memory location which it wants to access for reading and writing purpose. Data Bus The data bus is used to transmit data from the memory to microprocessor and from microprocessor to memory. The data bus is also used to transmit data to other devices such as output units. The data bus is bidirectional because data has to pass from microprocessor to memory as well as from memory to the microprocessor. So the data is transmitted in both the directions. Control Bus The control bus controls the transmission of data. The control bus supervises the reading and writing of data. It transmits signals to all the devices at the proper time. It keeps informed the control unit about the status of a particular job or task. =============Long Questions and Answers========== Q1. Describe the major components of digital computers? The computer system is a complex computing device. It involves some major components for the processing of data. There are the primary components and without these components the processing cycle cannot be completed. Components Of Digital Computer: The following are the components of a digital computer: Input Unit Output Unit Central Processing Unit Memory Unit Input Unit Data and commands can be entered into computer system through input unit. The input unit provides an interface between the user and the machine. Page 56 of 157 VER: 04.

[Audio] Example Keyboard is the most common example for the input unit. But data can be entered using various input devices and in many forms like audio, video and graphical. Output Unit The output unit receives information and data from the central processing unit for the user. It also provides an interface between machine and user. Digital data is converted into audio, visual and graphical form by the output device for the user. Example Monitor is the most common example for the output unit. Various devices are used for audio, video and graphical output. Central Processing Unit The Central Processing Unit is the brain of the computer system. It has two major sections, an ALU and Control Unit. It also contains several registers and a network of buses connecting various components. The CPU works with the co-ordination of memory unit to carry out the processing tasks. Example Now-a-days, a PGA shape processor is inserted into the ZIF socket on the motherboard. Memory Unit A volatile memory unit plays an important role for the processing of data. Memory unit is also called main memory. The following are the tasks assigned to the memory unit: To hold programs and data passed to the computer system for processing To hold the intermediate processing results To pass the process data and to hold output for the output unit. Example SIMM, DIMM and DDR chips of RAM are the examples of Memory unit. Page 57 of 157 VER: 04.

[Audio] Q2. Define registers? Explain various registers of CPU. Registers Registers are the temporary storage device which holds data and instructions until it is being processed or manipulated. Explanation Each register within the CPU performs a specific role. The registers help in the processing of data. The register's size and operations that take place in the register reflects the specific function that the register performs in the computer. Types Of Registers Following are some types of registers: General Purpose Registers Accumulator Status Registers Memory Buffer Registers Memory Address Registers Instruction Registers Program Counter Stack Pointer General Purpose Registers The general purpose registers may be used for temporarily storing data. These registers may be combined to form registers pairs in order to handle larger size data. These are also known as programmable registers as it may be programmed by the user with the help of instructions. Page 58 of 157 VER: 04.

[Audio] Accumulator The register is generally referred to as register AC. It is used for storing data for doing arithmetic and logic operations. The result of arithmetic and logical operations is automatically stored in this register. Status Register The status register is also called flag register, holds 1 bit flag to indicate certain conditions that arise during arithmetic and logical operations. The important conditions shown by flag or status registers are: CARRY : Indicates whether there is overflow or not ZERO : Indicates whether the result is zero or non zero SIGN: Indicates whether the result is plus or minus PARITY: Indicates whether the result contains odd number of 1s or even number of 1s. Memory Buffer Registers This register is also known as the Memory Data Register(MDR). It is used to hold a word that is being stored to or retrieved from the memory location currently addressed by the memory address register. Memory Address Registers This register holds the address of a memory location of the word to be written from or read into the MBR. Instruction Register This is very important register. It holds the actual instructions being executed currently by the computer system. Program Counter This is a register which deals with the order for execution of instructions. This acts like a pointer which indicates the subsequent memory locations where instruction is stored. After one instruction is executed the program counter gets incremented by one to indicate the location of the next instruction in the serial order. Stack Pointer Stack may be defined as a set of memory locations and the stack pointer may be defined as the indicator to these memory locations. Stack memory locations are used by a microprocessor for storing data temporarily for execution of a program. Q3. Define Bus. How many types of buses are there? Explain in detail. A bus is defined as the physical pathway for transmission of data and instructions in the central processing unit. Explanation The microprocessor contains various buses to locate memory location to read and write data. The buses inside the microprocessor are called Internal Buses. A bus is a communication pathway connecting two or more devices. A bus is a shared transmission medium. Physically a bus is a wire through which electronic signals can be transmitted. Types of Buses The following are three types of buses:  Address Buses The address bus is used by the microprocessor to transmit the address of the memory location which it wants to access for reading and writing purpose. Page 59 of 157 VER: 04.

[Audio] Example The microprocessor wants to read the contents of a memory location at the address 2012. This address coded in binary form is transmitted to all the devices connected to the microprocessor by the address bus only and microprocessor locates the particular memory location. An address bus is unidirectional, means electronic signals are transmitted in one direction only from microprocessor to other devices.  Data Bus The data bus is used to transmit data from the memory to microprocessor and from microprocessor to memory. The data bus is also used to transmit data to other devices such as output units. The data bus is bidirectional because data has to pass from microprocessor to memory as well as from memory to the microprocessor. So the data is transmitted in both the directions.  Control Bus The control bus controls the transmission of data. The control bus supervises the reading and writing of data. It transmits signals to all the devices at the proper time. It keeps informed the control unit about the status of a particular job or task. Q4. Explain internal working of CPU? OR Describe fetch cycle or execute cycle inside the CPU. The microprocessor is a complex computing device. It is the heart of the computer. Functions of CPU The CPU is the main processing device inside the computer system. It accepts data and instructions, process the data according to the instructions and delivers the output to the output unit. The CPU controls and co-ordinates the activities of all the units of computer system. Components of CPU: The central processing unit contains the following components: Control Unit ALU Cache Memory CPU Registers Math Co-processors All the above components work together for the processing of data. Features of a Digital Computer To understand the internal working of a computer system following features must be considered. The computer word is 16 bit long It accepts and executes one address instruction The instruction word is divided into two parts namely the operation code (Opcode) and address field which gives the address of the operant. The Opcode is 4 bit long and address field is 12 bit long The computer system has memory size of 4k words which means it has 4*1024=4096 memory locations which can be addressed. Page 60 of 157 VER: 04.

[Audio] Procedure of Instruction Processing The execution of an instruction stored in memory involves two steps. The processor reads instructions from memory on at a time and executes each instruction. Instruction Cycle The processing required for a single instruction is called Instruction cycle. Here instruction cycle has been represented with diagram. It involves the following two steps.  Fetch Cycle The fetch cycle is that duration of time in which an instruction stored in the memory is brought to an appropriate register. All this happens under the commands from control unit of the CPU. The process of bringing an instruction from memory to a register is called a fetch cycle. It has to be completed in specified duration of time.  Execute Cycle The process of execution of an instruction by the CPU in a specified interval of time is called execute cycle. The instruction fetched from memory is placed in a register where it is decoded and executed by ALU in the execute cycle. The CPU when fetching an instruction is set to be in fetch stage and while executing an instruction is in execute stage. These two stages appear alternately. Q5. Describe the procedure of execution of an instruction with diagram. An instruction cycle (sometimes called fetch-and-execute cycle) is the basic operation cycle of a computer. It is the process by which a computer retrieves a program instruction from its memory, determines what actions the instruction requires, and carries out those actions. This cycle is repeated continuously by the central processing unit (CPU), from bootup to when the computer is shut down. Explanation The fetch cycle brings the instruction to the instruction register, which holds this instruction temporarily as long as it is being interrupted and executed. Circuits used The circuits used in the CPU during the cycle are:  Program Counter (PC) - an incrementing counter that keeps track of the memory address of which instruction is to be executed next.  Memory Address Register (MAR) - holds the address in memory of the next instruction to be executed.  Memory Data Register (MDR) - a two-way register that holds data fetched from memory (and ready for the CPU to process) or data waiting to be stored in memory.  Instruction register (IR) - a temporary holding ground for the instruction that has just been fetched from memory.  Control Unit (CU) - decodes the program instruction, selecting machine resources such as a data source register and a particular arithmetic operation, and coordinates activation of those resources.   Page 61 of 157 VER: 04 .

[Audio]  Arithmetic logic unit (ALU) - performs mathematical and logical operations. Instruction cycle Each computer's CPU can have different cycles based on different instruction sets, but will be similar to the following cycle: 1. Fetch the instruction The next instruction is fetched from the memory address that is currently stored in the Program Counter (PC), and stored in the Instruction register (IR). At the end of the fetch operation, the PC points to the next instruction that will be read at the next cycle. 2. Decode the instruction The decoder interprets the instruction. During this cycle the instruction inside the IR (instruction register) gets decoded. 3. Read the effective address In case of a memory instruction (direct or indirect) the execution phase will be in the next clock pulse. If the instruction has an indirect address, the effective address is read from main memory, and any required data is fetched from main memory to be processed and then placed into data registers. If the instruction is direct, nothing is done at this clock pulse. If this is an I/O instruction or a Register instruction, the operation is performed (executed) at clock Pulse. 4. Execute the instruction The CU passes the decoded information as a sequence of control signals to the relevant function units of the CPU to perform the actions required by the instruction such as reading values from registers, passing them to the ALU to perform mathematical or logic functions on them, and writing the result back to a register. If the ALU is involved, it sends a condition signal back to the CU. The result generated by the operation is stored in the main memory, or sent to an output device. Based on the condition of any feedback from the ALU, Program Counter may be updated to a different address from which the next instruction will be fetched. Page 62 of 157 VER: 04.

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[Audio] CHAPTER EIGHT CHAPTER EIGHT CHAPTER EIGHT CHAPTER EIGHT 8 COMPUTER COMPUTER COMPUTER COMPUTER NETWORKS NETWORKS NETWORKS NETWORKS OBJECTIVE: When you have completed this chapter, you will be able to know about the Short Answer Questions Q1. Define the term computer network. Q2. What is a LAN structure? Describe famous LAN models. Q3. Define topology? What are various topologies used for networks? Q4. What do you know about hybrid topology? Q5. Define protocol. Why protocols are used describe with examples. Q6. What is the (www) world wide web? Q7. What is a web browser? Describe with example. Q8. What do you know about extranet? Q9. What do you know about intranet? Long Answer Questions Q1. Define network. Why network are used? Q2. How many types of networks are there? Explain each of them? Q3. Define LAN. Write down important characters of LAN. Q4. What is network operating system describe with example? Q5. What is a LAN structure? Describe features of famous LAN models. Q6. What is star topology? What are its advantages and disadvantages? Q7. What is a ring topology? What are its advantages and weakness? Q8. What is a bus topology? What are its advantages or disadvantages? Q9. What are different network components of a LAN? Explain in detail. Q10. Describe the purpose of various network devices like NICs, Repeaters, Hubs, Switches, Bridges, Routers and Firewalls. Q11. Define internet. Write down major advantages of internet. Q12. Define email. Write down its advantages and disadvantages. Page 64 of 157 VER: 04.

[Audio] CHAPTER # 8 COMPUTER NETWORKS =============Short Questions and Answers========== Q1. Define the term computer network. Computer Network When two or more computers are connected to each other by cables or wirelessly to share resources, it is called a computer network. Explanation Computers are connected to each other mainly for the sack of communication and resources sharing. A resource may be a hardware or software. Example  LAN of an office   WAN of a bank  GAN the internet Q2. What is a LAN structure? Describe famous LAN models. LAN Structure / LAN Models A LAN structure defines what type of role has been provided to the nodes of the LAN. The LAN model is apart from the physical layout of the LAN. The following are the two major types.  Peer To Peer Network In this network model all the nodes have equal rights and can directly communicate with one another. A peer to peer network is also called work group.  Client Server Network In a client server network one or more computers are installed as server and all the other nodes are called clients. A sever is a high capacity, high speed machine which provides services to the nodes. Q3. Define topology? What are various topologies used for networks? A topology is the physical layout of computer system, cables and network devices in a LAN. OR The physical arrangement of nodes in a network is called topology. Explanation The networks can be developed using various methods. Apart from the network models the topology defines the physical connection among the nodes. Types Of LAN Topology The following are the four basic topology used for LAN.  Star Topology   Ring Topology  Bus Topology   Hybrid Topology Page 65 of 157 VER: 04.

[Audio] Q4. What do you know about hybrid topology? Hybrid Network Topology Hybrid network topology is a combination of two or more topologies. Explanation In hybrid network topology there may be a combination of two or more topologies like star topology, ring topology and bus topology. When two LANs (local area network) of star topology are connected through a cable from the central unit. It becomes star bus topology. Q5. Define protocol. Why protocols are used describe with examples. Rules and regulations applied for effective communication over the network are called protocols. Explanation A protocol defines the proper method of communication among the computers of a networks. The protocol provides error free, secure, fast and effective communication. A number of protocols have been defined for different purposes. Examples FTP: file transfer protocol SMTP: simple mail transfer protocol. TCP/IP: transmission control protocol/ internet protocol. Q6. What is the (www) world wide web? World wide web is the collection of hyper text documents. Explanation Over the internet the hyper text documents called web pages can be accessed. These web pages are published by companies or individuals containing information about different topics. A web browser felicitates to open web pages. Example www.google.com www.hotmail.com www.yahoo.com Page 66 of 157 VER: 04.

[Audio] Q7. What is a web browser? Describe with example. A web browser is an application software which provides the facility to interact with the web pages. Explanation: A web browser is sent to open web sites. It displays text, images and other information one web page over the world wide web or in a local area network. A web browser enables a user easily and quickly accesses a web page. Examples Internet explorer Netscape navigator Google chrome Q8. What do you know about extranet? An extranet is a computer network that allows controlled access from the outside, for specific business or educational purposes. An extranet can be viewed as an extension of a company's intranet that is extended to users outside the company, usually partners, vendors, and suppliers. It has also been described as a "state of mind" in which the Internet is perceived as a way to do business with a selected set of other companies (business-tobusiness, B2B), in isolation from all other Internet users. In contrast, business-to-consumer (B2C) models involve known servers of one or more companies, communicating with previously unknown consumer users. Q9. What do you know about intranet? An intranet is a set of networks, using the Internet Protocol and IP-based tools such as web browsers and file transfer applications, that is under the control of a single administrative entity. That administrative entity closes the intranet to all but specific, authorized users. Most commonly, an intranet is the internal network of an organization. A large intranet will typically have at least one web server to provide users with organizational information. ===========Long Questions and Answers========= Q1. Define network. Why network are used? Computer Network When two or more computers are connected to each other by cables or wirelessly to share resources, it is called a computer network. Explanation Computers are connected to each other mainly for the sake of communication and resources sharing. A resource may be a hardware or software. Page 67 of 157 VER: 04.

[Audio] Reasons to Develop Network 1. The very first objective to develop a network is to get communication. Two computers can communicate each other. 2. Hardware resources like printers, scanners and digital cameras can be sheared over the network. 3. Data files can be shared over the network. 4. The software can also be shared among different computers of the network. 5. Because of the resources sharing cost of devices can be saved and performance can be increase. Q2. How many types of networks are there? Explain each of them? The computer networks may be of the following three types. 1. LAN (local area network) 2. WAN (wide area network) 3. GAN (global area network) LAN (Local Area Network) A group of computers connected to each other in a small geographic area like home or office is called LAN. Explanation A local area network is normally owned privately. The systems are connected wirelessly or through cables. Special network software are installed to run the whole setup. Example 1. A LAN (in any business office) 2. A computer lab (in an educational institute) WAN (Wide Area Network) A WAN is a computer network developed over a wide geographical area which can cover cities, states or countries. Explanation WANs are normally used in large corporations to facilitate the exchange and on time update of data. It also enables LANs to communicate with each other. Examples A country wide WAN of a bank. GAN (Global Area Network) A GAN is a worldwide interconnection of computer networks. Explanation A GAN is the network of the networks through out the world. We also referred to it as internet. A GAN follows specific standard called protocols for communication. It is a public network. Examples Internet Q3. Define LAN. Write down important characters of LAN. A LAN is a privately owned computer network in a small geographic location. Explanation A LAN is developed normally inside an office or home. The computer systems are connected by wirelessly or with wired media. Page 68 of 157 VER: 04.

[Audio] Characteristics of a LAN The following are some major characteristics of a LAN.  Small Geographic Location LANs are developed in a building, house or office. It means that it is developed in a small geographic area.  LAN Machines The computer systems connected in a LAN are called nodes. A node which provide services is called server machine and a node which receives services is called client machine or work station.  Network Software In a LAN special operating systems are installed on the nodes. There are different client and server operating systems.  Resources Sharing The computer systems connected in a LAN can share the resources like data files, hardware and software.  Policy Based Management In a LAN all the systems in an organization can share a uniform policy and policy based management. A person who controls, implements and manages a LAN is called LAN administrator. Q4. What is network operating system describe with example? An operating system which is particularly designed for a network is called network operating system. Explanation A network operating system contains special features applied on a network. A network operating system is more advanced then an individual operating system. Network Operating System Types There are mainly two types of network operating systems these are as follows:  Server Operating System An operating system which manages all the client machines and provides services is called server operating system. It implements policies, user rights, restrictions and permission for work stations. Examples Windows 2003 server Windows 2008 server  Client Operating System An operating system installed on a work station to get services from the server is called client operating system. Example Windows XP 2003 Windows NT workstation Q5. What is a LAN structure? Describe features of famous LAN models. LAN Structure / LAN Models A LAN structure defines what type of role has been provided to the nodes of the LAN. The LAN model is apart from the physical layout of the LAN. The following are the two major LAN models. 1. Peer To Peer Network. (Work Group) 2. Client Server Network (Domain) Page 69 of 157 VER: 04.

[Audio] 1. Peer To Peer Network In this network model all the nodes have equal rights and can directly communicate with one another. A peer to peer network is also called work group. Features 1. There are equal rights and authorities among the nodes. 2. There is not any node as server. 3. Peer to peer network is less expensive. 4. Peer to peer network can work effectively up to 25 nodes. 5. Peer to peer network is useful for small organizations. Examples o AppleShare used for networking connecting Apple products. o Windows for Workgroups used for networking peer-to-peer windows computers. Advantages  Ease of setup  Less hardware needed, no server needs to be purchased. Disadvantages  No central location for storage.  Lack of security that a client/server type offers. 2. Client Server Network In a client server network one or more computers are installed as server and all the other nodes are called clients. A sever is a high capacity, high speed machine which provides services to the nodes. Page 70 of 157 VER: 04.

[Audio] Features 1. All the nodes depend on a computer system called server. 2. The computer which gets services from the servers are called client. 3. For all the nodes the policies, user rights and permissions are imposed from the server. 4. Centralized control of the network is manages easily. 5. Centralized storage of data provides easy backup management. 6. In client server model a network of thousands of computers can be developed and manage easily. Examples  Novell Netware  Windows Server  Advantages   Centralized servers are more stable.  Security is provided through the server.  New technology and hardware can be easily integrated into the system.   Servers are able to be accessed remotely from different locations and types of systems. Disadvantages  Cost of buying and running a server are high.   Dependence on a central location for operation.  Requires regular maintenance and updates.   Q6. What is star topology? What are its advantages and disadvantages?  In a star topology the nodes are connected to a central unit which may be devices like hub, switch or it may be a computer system having multiple network interfaces. The central unit is responsible for the communication among the nodes of the network.     Page 71 of 157 VER: 04 .

[Audio] Advantages Of Star Topology The star topology is a most commonly used topology for a network and it has a number of advantages.  Easy Installation Of Nodes In a star network nodes can be added and removed easily, and the physical management of the network is quite comfortable.  No Chance Of Data Collision While using a star topology in a network there is no chance of data collision because central unit presents the collision of data.  No Influence Of Any Connection Failure If any node is failed to work or any connection is broken from any node or device the whole network is not affected and work continuously.  No Transmission Delay If the number of nodes are increased it does not affect the speed of the network because all the traffic passes through the central unit. Disadvantages Of Star Topology The star topology contains some weaknesses which are as follows:  Total Dependency On The Central Unit A star network is particularly dependent on the central unit like hub or switch. If the switch fails to work the whole network will be stopped.  Expensive Hardware Since a separate cable for each computer is required so it becomes comparatively expensive. Similarly, the central unit is also compulsory which increases cost. Page 72 of 157 VER: 04.

[Audio] Q7. What is a ring topology? What are its advantages and weakness? Ring Topology In a ring topology the nodes are connected with each other in such a way that the structure look likes a ring. Explanation In ring topology all the nodes are connected in a ring like structure. The communications between the nodes follow a clockwise or anticlockwise pattern. The data passes through node to node to reach the desired destination. The ring topology does not contain a central unit. Advantages Of A Ring Network The ring network contains the following advantages.  No Danger Of Data Collision The data flows in a single direction so there is no chance of collision of data.  No Dependence On Central Unit Unlike the star network the communication is not dependent on the central unit, so a ring network is more reliable in this regard. Disadvantages Of Ring Network The following are the disadvantages of the ring network.  Communication Delay: There is a direct proportion between the number of nodes and communication delay. So as the number of nodes increase, it results in more communication delay.  Difficult Network Extension In a ring network it is not so easy to add or remove the new terminals.  Difficult Trouble Shooting As compare to the star network it is difficult to trouble shoot any communication problem in a ring network.  Total Dependency On The Ring If the ring is broken the whole network stops working. Page 73 of 157 VER: 04.

[Audio] Q8. What is a bus topology? What are its advantages or disadvantages? Bus Topology In a bus topology the nodes are connected in a series on a network cable. Explanation In a bus topology all the computers and devices are connected on a network cable. Usually a circuit board or card is used to connect one of the expansion slot. The card contains the hardware and software required to access the network. All the communication take place on a common network cable. In a bus network there is no central unit. Advantages Of Bus Network The bus network contains the following advantages.  Easy Extension Of Networks The new terminals can be added or removed easily in a bus network.  Easy Network Management A bus network is simple and it is easy to administrate.  No Influence Of Any Node Failure In a bus network if one of the terminal become defective it does not effect on other computers of the networks. Disadvantages Of Bus Network A bus network contains the following weaknesses.  Extra Hardware And Software Requirement In a bus network extra circuitry and software are required to avoid collision of data.  Difficult Error Detection If any error is produced in a network it is not easy to detect.  Total Dependency On Main Cable If a connection in the bus network is broken the entire network may stop working. Q9. What are different network components of a LAN? Explain in detail. A local area network is developed using several standard components. These components can be categorized mainly as. 1. Software Components 2. Hardware Components Software Components When a computer network is developed special softwares are required to run a network effectively. Network Operating System A network operating system is an special operating system designed specifically to install on the nodes of the network. It manages all the activities of the computer system and communication. Special Purpose Network Software In computer network special purpose network software are also installed to get advantages like communication and network Page 74 of 157 VER: 04.

[Audio] protection. Anti-viruses, emailing and file transferring softwares are the examples. Hardware Components In order to develop a computer network besides the computer system some hardware are also required. These are as follows:  Connection Cables To develop a LAN special cables are required to connect the computer systems. Twisted pair cables, ca-axial cable or fiber-optic cables can be used to connect computer systems. The connection among the computer systems can also be wireless connection using infra-red, radio-ware, Bluetooth or wifi.  Network Interface Card Network interface card is a small circuit board which is inserted in any expansion slot. It is abbreviated as NIC. It provides the processing features for communication among the computers in a network. 3com, zoltrix and smartlink are the examples of NIC.  Special Purpose Network Devices: For proper management, control and administration some special purpose network devices are used. These devices perform the task like regenerating of signals, boosting of the information packets and providing error free communication. The examples include routers, bridges and gateways.  Shared Devices Some peripheral devices are also installed in a network to get the advantage of sharing. These devices can be shared by all the computer systems connected with the network. Examples include printers, scanners, fax machines and storage devices etc. Q10. Describe the purpose of various network devices like NICs, Repeaters, Hubs, Switches, Bridges, Routers and Firewalls. Apart from the physical communications media themselves as described above, networks comprise additional basic hardware building blocks interconnecting their terminals, such as network interface cards (NICs), hubs, bridges, switches, and routers. Network Interface Cards A network card, network adapter, or NIC (network interface card) is a piece of computer hardware designed to allow computers to physically access a networking medium. It provides a low-level addressing system through the use of MAC (Media Access Control) addresses. Each Ethernet network interface has a unique MAC address which is usually stored in a small memory device on the card, allowing any device to connect to the network without creating an address conflict. Ethernet MAC addresses are composed of six octets. Uniqueness is maintained by the IEEE. Repeaters and Hubs A repeater is an electronic device that receives a signal, cleans it of unnecessary noise, regenerates it, and retransmits it at a higher power level, or to the other side of an obstruction, so that the signal can cover longer distances without degradation. In most twisted pair Ethernet configurations, repeaters are required for cable that runs longer than 100 meters. A repeater with multiple ports is known as a hub. Repeaters work on the physical layer of the OSI model. Repeaters require a small amount of time to regenerate the signal. Page 75 of 157 VER: 04.

[Audio] This can cause a propagation delay which can affect network communication when there are several repeaters in a row. Today, repeaters and hubs have been made mostly obsolete by switches. Bridges A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. Bridges broadcast to all ports except the port on which the broadcast was received. However, bridges do not promiscuously copy traffic to all ports, as hubs do, but learn which MAC addresses are reachable through specific ports. Once the bridge associates a port and an address, it will send traffic for that address to that port only. The first time that a previously unknown destination address is seen, the bridge will forward the frame to all ports other than the one on which the frame arrived. Bridges come in three basic types:  Local bridges: Directly connect local area networks (LANs)   Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced with routers.   Wireless bridges: Can be used to join LANs or connect remote stations to LANs. Switches A network switch is a device that forwards and filters OSI layer 2 datagrams (chunks of data communication) between ports (connected cables) based on the MAC addresses in the packets. A switch is distinct from a hub in that it only forwards the frames to the ports involved in the communication rather than all ports connected. A switch breaks the collision domain but represents itself as a broadcast domain. Switches make forwarding decisions of frames on the basis of MAC addresses. A switch normally has numerous ports, facilitating a star topology for devices, and cascading additional switches. Some switches are capable of routing based on Layer 3 addressing or additional logical levels; these are called multi-layer switches. Routers A router is an internetworking device that forwards packets between networks by processing information found in the datagram or packet (Internet protocol information from Layer 3 of the OSI Model). In many situations, this information is processed in conjunction with the routing table (also known as forwarding table). Routers use routing tables to determine what interface to forward packets (this can include the "null" also known as the "black hole" interface because data can go into it, however, no further processing is done for said data). Firewalls A firewall is an important aspect of a network with respect to security. It typically rejects access requests from unsafe sources while allowing actions from recognized ones. The vital role firewalls play in network security grows in parallel with the constant increase in 'cyber' attacks for the purpose of stealing/corrupting data, planting viruses, etc. Gateways A gateway is an interface which enables dissimilar networks to communicate each other. A gateway may be a device or software configured on a computer system. Page 76 of 157 VER: 04.

[Audio] Dissimilar network means networks having different topologies or operating system. For example Microsoft configured gateway. Q11. Define internet. Write down major advantages of internet. Internet The internet is a global area network. It is the network of the networks. Explanation The internet was evolved from a network called "ARPANET". It was developed in 1969 by US department of defense. With the passage of time the protocols were established for communication. In 1983 a standard protocol with the name of TCP/IP was developed and in 1990 ARPANET was commercially introduced as internet. Advantages Of Internet Internet provides a number of benefits, these are as as follows:  Easy Method Of Communication Internet provides easy methods for communication which are assembled by all kinds of communities.  Cheap Method For Communication Internet provides fast and inexpensive methods for communication.  Sharing Of Information Using internet public information can be shared using World Wide Web.  On Time Transmission Data can be shared on time using various methods of internet. There no chance of delay.  Online Data Processing Online data processing for business like banks, utility bills etc are performed easily through internet.  Online Sales And Purchase Online sales and purchase is an advanced feature of internet.  Voice And Video Communication Besides the PSTN (public switch telephone network). Internet provides inexpensive and fast voice communication and video conferencing facility. Q12. Define email. Write down its advantages and disadvantages. Transformation of text messages over the internet is called e-male. Page 77 of 157 VER: 04.

[Audio] Explanation The most of the websites allow users popular allows users to send and receive messages to each other using e-mail. The electronic file can also be sent and received using email. An e-mail address is developed on a website called domain. It contains the user name and the domain name. The user name identifies the person who originates or receives the mail. The domain name identifies the computer system on which the user has on account. The e-mail address' parts are separated be @ and .sign. Example [email protected] Advantages Of E-Mail The following are some advantages of e-mail.  Speedy Transmission An email is delivered at the moment when it is sent. There is not any other such kind of fast mail delivery system.  Inexpensive Transmission Electronic files and letters can be sent and received on a very less cost.  Availability The facility is available normally every time and everywhere.  Flexible Management It is easy to send and receive mail a number of features are provided by the email service providers. Disadvantages Of E-Mail The following are some disadvantages of e-mail.  Email facility is generally available to everyone.  Any email send to wrong address cannot be recalled back .   It is not completely private or confidential due to hacking.  It can be misused because it is free of cost.   An email may contain any virus or file that can affect the computer system. Page 78 of 157 VER: 04.

[Audio] CHAPTER NINE CHAPTER NINE CHAPTER NINE CHAPTER NINE 9 DATA DATA DATA DATA COMMUNICATION COMMUNICATION COMMUNICATION COMMUNICATION OBJECTIVE: When you have completed this chapter, you will be able to know about the Short Answer Questions Q1. Define Data Communication? Describe communication Model. Q2. How many types of signals are there in data communication? Q3. What do you know about bandwidth? Also describe the types of the bandwidth. Q4. Define communication medium? Explain various communication medium? Q5. What is wireless communication? Long Answer Questions Q1. Define Data Communication? Describe communication Model. Q2. How many types of transmissions are there regarding direction of transmission? Q3. What do you know about bandwidth? Also describe the types of the bandwidth. Q4. Describe the various transmission modes in detail. Q5. What is wired communication media? Explain the structure and features of twisted pair cables. Q6. What is wired communication media? Explain the structure and features of co-axial cable. Q7. What is wired communication media? Explain the structure and features of fiber optic cable. Q8. What is wireless communication? Explain microwave transmission. Q9. What is wireless communication? Explain satellite transmission. Q10. What is OSI model? Explain different layers of OSI model. Q11. Explain various communication hardware. Q12. What are the various communication software? Explain in detail. Page 79 of 157 VER: 04.

[Audio] CHAPTER # 9 DATA COMMUNICATION ===========Short Questions and Answers========= Q1. Define Data Communication? Describe communication Model. Data Communication Data Communication or Telecommunication is a process of transmitting and receiving data using technology across a distance. Explanation In Data Communication, the data is sent from a source to destination. The data may be in the form of text, images, voices or videos. The data communication is a study of data transmission using computer system Data Communication Model The data communication model includes the following elements for complete and effective communications.  Source  Transmitter   Medium  Message   Receiver  Destination Q2. How many types of signals are there in data communication? The following are the two types of signals used in communication technology. Analog Signal An analog signal is continuous electrical signal in the form of a wave. Explanation An analog signal contains the characteristics of a wave. The wave is in the form of crust and trough. The height of wave from its mean position to extreme position is called amplitude. The number of cycles completed in one second is called frequency of analog signal. Digital Signal A digital signal is represented by a discrete number 0s and 1s. Explanation 0 1 0 1 0 1 0 1 0 1 0 10 A digital signal is not in the form of a wave. It is generated by electric pulses in the form of represent low and very low voltages of current. Page 80 of 157 VER: 04.

[Audio] Q3. What do you know about bandwidth? Also describe the types of the bandwidth. Bandwidth is defined as the capacity of a media for transmission and handling of data. Explanation The Bandwidth defines the capacity of data transmission for the cables used in a network. Bandwidth is the range of frequencies that is available for the transmission of data. Types of Bandwidth The following are the three major types of Bandwidth  Narrow Band  Voice Band   Broadband Q4. Define communication medium? Explain various communication medium? The communication medium is the thin through which the data is transferred from source to destination. Types of Communication Media The following are the major types of communication media. Wired Communication Media In wired communication special purpose cables are used for the transmission of data Example  Twisted Pair Cable   Co-Axils Cable  Fiber Optic Cable Wireless Communication media In wireless communication special purpose equipment are used to send and receive data. Data is sent wirelessly in the form of a signal depending on the technology being used. Example 1. Microwave 2. Satellite Q5. What is wireless communication? Wireless communication media In wireless communication special purpose equipment are used to send and receive data without using wires. Data is sent wirelessly in the form of a signal depending on the technology used. Types of transmission The following are the most commonly used communication media for wireless communication. Microwave Transmission Satellite Transmission Page 81 of 157 VER: 04.

[Audio] =============long Questions and Answers=========== Q1. Define Data Communication? Describe communication Model. Data Communication Data Communication or Telecommunication is a process of transmitting and receiving data using technology across a distance. Explanation In Data Communication, the data is sent from a source to destination. The data may be in the form of text, images, voices or videos. The data communication is a study of data transmission using computer system Data Communication Model The data communication model includes the following elements for complete and effective communications. Source The entity which wants to sent data is called source. When a person is speaking to someone he is the source. Diagrammatic Representation of Communication Model Transmitter Transmitter is a device which sends the data from the sender or source it means that it performs the task of encoding. For example, when a person speaks his tongue is transmitter. Medium The medium is the thing through which data is transmitted. For example, when a person speaks, the air is the medium through which sound wave is passed. Message The data which is sent by the source is called message. For example, when a person speaks, the spoken words contain the message. Receiver The Receiver is a device which receives the data and decodes it in the form which is readable by the destination. For example, when a person is speaking to another person, the other person's ear is the receiver. Destination The entity which receives the data through receiver is called destination. For example, when a person speaking to another person, the other person is the destination. Q2. How many types of transmissions are there regarding direction of transmission? The Data direction in a transmission can be unidirectional or bidirectional. There are following three types of transmission on the basis of direction. Page 82 of 157 VER: 04.

[Audio] o Simplex Transmission o Half Duplex Transmission o Full Duplex Transmission Simplex Transmission The simplex transmission contains the transmission of data in only one direction.  Explanation It is a one way or unidirectional transmission. A device connected in such transmission is either a sent only or received only device.  Example Transmission of Television Transmission of Radio Half Duplex Transmission The half duplex transmission contains the transmission of data in two way direction.  Explanation Although the data is transmitted in two ways direction, but one direction at a time. So, half duplex communication is bidirectional but device connected to such transmission can be either a sending device of receiving device at a time.  Example Wireless Transmission system CB Radio System Full Duplex Transmission In full duplex Transmission the data is transmitted in both the directions simultaneously.  Explanation The Full duplex transmission is faster than simplex and half duplex. It is also more expensive. Full duplex transmission is commonly used today and easily available.  Example Cell Phones Transmission Micro Computer Transmission Q3. What do you know about bandwidth? Also describe the types of the bandwidth. Bandwidth is defined as the capacity of a media for transmission and handling of data. Explanation The Bandwidth defines the capacity of data transmission for the cables used in a network. Bandwidth is the range of frequencies that is available for the transmission of data. Types of Bandwidth The following are the three major types of Bandwidth  Narrow Band The Narrowband communication media contains relatively slow speed for transmission of data. The telegraph lines are the example of narrowband.  Voice Band The Voice band communication media is faster than the narrowband. Most telephone lines used today have the voice band communication media. It can be used for microcomputer transmission of data. Page 83 of 157 VER: 04.

[Audio]  Broadband This communication media can transmit huge amount of data at very high speed Co-Axial Cable, Fiber Optic and Satellite are the example of broadband communication. Q4. Describe the various transmission modes in detail. Transmission Mode The Transmission mode defines that in which form the data is transmitted from source to destination in a computer network. Types of Transmission Modes The following are the two types of transmission modes. Asynchronous Transmission In this transmission mode data is sent one byte at a time.  Explanation In asynchronous transmission data is transmitted byte by byte means 1 byte at a time. Each byte consists of 8 bits and it is preceded by a 'start' bit and 'stop' bit. This transmission mode is inexpensive but relatively slow. It is widely used in micro-computers. Synchronous Transmission In this transmission mode data is transmitted in the form of blocks or packets.  Explanation In synchronous transmission data is transmitted in the form of packets. A packet may contain several bytes but there is no 'start' or 'stop' bit. Synchronous transmission is used by large computers. It is used to transmit great volume of data. Synchronous transmission is expensive but contains very high speed. Complex and expensive timing devices are used in this transmission mode. Q5. What is wired communication media? Explain the structure and features of twisted pair cables. Wired Communication Media In wired communication special purpose cables are used for communication. Types Of Data Cables The following are the most commonly used cables for communication. Twisted Pair Cables Co-axial Cables Fiber Optic Cables. Twisted Pair Cable The twisted pair cable is a communication media which provide relatively slow but error free communication. Structure Twisted Pair Cables consists of two wires individually insulated in plastic then twisted around each other and bound together in another lair of plastic insulation. Page 84 of 157 VER: 04.

[Audio] Advantages and characteristics Effective Communication In short ranges the twisted pair cables provides effective communication.  Error Free Communication In short distance it provides error free communication.  Easy Installation Twisted pair cables are very easy to install.  Inexpensive Twisted pair cables are comparatively inexpensive and easily affordable.  Use It can be used not only for voice but also in computer networks. Disadvantages  It does not perfectly control the noise interference which can disturb the signals.   In order to use twisted pair cables for long distance, needs a signal regenerating device called repeater.   The data communications through twisted pair cables are relatively slow. Q6. What is wired communication media? Explain the structure and features of co-axial cable. In wired communication special purpose cables are used for communication. Types Of Data Cables The following are the most commonly used cables for communication. Twisted Pair Cables Co-axial Cables Fiber Optic Cables. Co-axial cables The co-axial cable is a communication media which provide relatively fast communication in television and computer networks. Structure The co-axial cable consists of insulated copper wire wrapped in a wire mesh shield, then in an external cover. The wire mesh shield Is in between the insulator and plastic cover. Page 85 of 157 VER: 04.

[Audio] Advantages and Characteristics  Higher Bandwidth The co-axial cable provides higher bandwidth for communication.  Support Transmission  It supports transmission speed up to 10 megabits per second.  Protection Against Noise Interference  Co-axial cable is best known for its protection against noise interference.   Data Carrying  It can carry more data than older types of twisted pair cables. Disadvantages  Co-axial cable is expensive as compare to twisted pair cables.   It is used in a limited geographical area. Q7. What is wired communication media? Explain the structure and features of fiber optic cable. In wired communication special purpose cables are used for communication. Types Of Data Cables The following are the most commonly used cables for communication. Twisted Pair Cables Co-axial Cables Fiber Optic Cables. Fiber optic cables The fiber optic cable is a communication media that transmits digital data in the form of modulated pulses of light. Structure The optical fiber consists of an inner cylinder of glass which is called core. The core is actually propagating path for the light. It is surrounded by a cylindrical shell of glass or plastic of lower refractive index which is called cladding. Data transmission The transmission of light through a fiber is based on total internal reflection, which occurs when light is incident at an interface between two mediums of different refractive indexes at an angle greater than critical angle. Page 86 of 157 VER: 04.

[Audio] Advantages and Characteristics  Transmission Of Data The fiber optic cables transmit data faster than some other technologies.   Main Ingredient The main ingredient is glass which is prepared by sand and it is easily available in the world. So its material is comparatively inexpensive and light.   Form Of Transmission  Since, the data is transmitted in the form of light through the fiber optics, so it s safer because there is no chance of spark and electrical shock.   Low Rate Of Errors  Since, the fiber optic carry light pulses, it is not affected by random electromagnetic interference in the environment. So there is lower rate of errors than other media.   Low Rate Of Transmission Loss The transmission loses in fiber optics are much lower than that of the twisted pair wires and co-axial cables.   Durable It is more durable than twisted pair and co-axial cables because it is immune to oxide degradation.   Security Of Data  It is more reliable for data security. Data cannot be tapped or stolen. Disadvantages  All fiber optic cables are limited to fixed point to point ground installation. They cannot leave the ground nor be associated with a mobile communication station.   Popular light emitting sources are restricted to very low power devices. There are high power devices available but they are very expensive.   The ways in which the light source can be modulated are limited because of low power sources. The distance between repeater/amplifier must be relatively short for high data rates demanded in some systems. Q8. What is wireless communication? Explain microwave transmission. Wireless Communication Media In wireless communication special purpose equipment are used to send and receive data without using wires. Data is sent wirelessly in the form of a signal depending on the technology used. Types Of Transmission The following are the most commonly used communication media for wireless communication. Microwave Transmission Satellite Transmission Microwave Transmission Microwave system transmits voice and data through the atmosphere at high frequency radio waves. Page 87 of 157 VER: 04.

[Audio]  Explanation Microwaves are the electromagnetic waves that vibrate at one gigahertz per second or higher. These frequencies are used to transmit messages between ground based earth stations and satellite communication systems since the microwave signals cannot bent so the microwave transmission is in a straight line, means in a line-ofsight. Moreover as the waves cannot bend, these are relayed by means of dishes or antennas installed on high buildings, towers and hilltops.  Ranges Microwave station needs to play within 40-50 kilometers of each other with no obstructions in between.  Example Nowadays most of the telephone system used dish microwave transmission. Q9. What is wireless communication? Explain satellite transmission. Wireless Communication Media In wireless communication special purpose equipment are used to send and receive data without using wires. Data is sent wirelessly in the form of a signal depending on the technology used. Types Of Transmission The following are the most commonly used communication media for wireless communication. Microwave Transmission Satellite Transmission Satellite Transmission Satellite transmission systems contain microwave relay stations in the orbit around the earth for communication. Explanation The satellite communication overcomes the major problem of microwave communication that is obstruction of signals. The obstruction of signals is caused by the curvature of earth, mountains and other structures that lock the line of sight. The microwave relay stations in the orbit of the earth are called SKY STATIONS. Which contain a component called TRANSPONDER. The transponder receives the transmission form earth station, amplifies the signals, and retransmits them to another earth station. The satellite contains many communication channels and receives both analog and digital signals from earth station. Ranges The satellite is launched by rockets and normally the orbit is 36,000 kilometers above the equator. If the satellites revolving speed is equal to earth rotation. It seems to be stationary in the space; hence the satellite is called GEOSTATIONARY. Example Hundreds of satellites are now in orbits to handle international and domestic data, voice, video communication needs. BADAR-1 and BADAR-2 are Pakistan's famous satellites. Page 88 of 157 VER: 04.

[Audio] Q10. What is OSI model? Explain different layers of OSI model. OSI model An international standard for communication defined by ISO (International Standard Organization) is called OSI (Open System Interconnection). Explanation This standard has been defined by ISO that simulates the communication process using seven layers, each with its own set of protocols. Purpose of OSI Model The purpose of OSI model is to enable any vender's computer system to share data with any other vender's computer system in an open networking environment. Structure of OSI Model The OSI model contains seven layers having there specified purposes. These layers are as follows; LAYER-1: Physical Layer LAYER-2: Data-Link Layer LAYER-3: Network Layer LAYER-4: Transport Layer LAYER-5: Session Layer LAYER-6: Presentation Layer LAYER-7: Application Layer Layer-1:- Physical Layer The physical layer controls the electrical, mechanical and functional transmission of bits over the data circuits.  Layer-2:- Data-Link Layer The data-link layer detects and compensates for transmission error and ensures that information sent by high speed transmitters is properly received by slow receivers.   Layer-3:- Network Layer The network layer determines how information is routed between computers and within and between individual networks. It also handles software interfaces between networks, including networks with different protocols.  Layer-4:- Transport Layer The transport layer specifies the rule for information exchange and manages end-to-end delivery if information within and between networks including error recovery. It also controls information flow. For example: - Multiple data streams on a single channel. Page 89 of 157 VER: 04.

[Audio]  Layer-5:- Session Layer The session layer controls the dialog between two computers, managing file transfer and putting checkpoints into a data stream to allow portions of files to be retransmitted as needed.  Layer-6:- Presentation Layer The presentation layer supplies transparent communication by masking difference in unlike data formats such as the ASCII and EBCDIC character codes, and performs data compression and encryption.  Layer-7:- Application Layer The Application layer supplies functions for particular applications such as file transfer, remote access, and virtual terminals. Q11. Explain various communication hardware. When two or more computer systems communicate each other, they need to have a communication hardware that is a device which control the flow of data. The following are some commonly used communication hardware. Modem Ethernet Fast Ethernet Token Ring Modem When the computer system communicates over the telephone line a device is required to control the flow of data which is called MODEM.  Explanation Since the computer systems communicate digitally it needs to have a device which can convert the digital signal into analog signal so that the signal can be transmitted on analog telephone lines.  Functions Of Modem The modem converts the digital signal into analog signal, this process is called MODULATION. Similarly analog signal into digital signal and this process is called DEMODULATION. The device had got the name MODEM (short for MODULATION/DEMODULATION).  Types Of Modem A modem may be internal or external. An external modem is a separate box and it is externally connected to the computer. An internal modem is a circuit board which is plugged in any expansion slot on the motherboard.  Transmission Speed The transmission speed of a modem is expressed in kilobits. A 128kbps and 256kbps are the commonly used speeds for the modem. Ethernet The Ethernet is the most common network technology used to connect two or more computers in a small geographic area. Page 90 of 157 VER: 04.

[Audio]  Explanation Ethernet was basically design for a bus topology and co-axial cable, but nowadays it is also available on star topology with twisted pair or fiber optic cables. With Ethernet, if two nodes transmit data simultaneously, the collision is detected; they retransmit one at a time. This approach to network communication is called CSMA/CD (Carrier Sense Multiple Access/Collision Detection).  Transmission Speed The original implementation of Ethernet which uses co-axial cable was called 10base-5 and 10base-2. The most popular implementation if Ethernet is 10bas-T that used star topology and twisted pair cables and can achieve transmission speed up to 10 mbps. Fast Ethernet An advanced form of Ethernet which can be used as different network interface cards is called FAST ETHERNET.  Explanation The fast Ethernet uses different types of media and topology as Ethernet. But it can be used for different network interface cards.  Transmission Speed It is normally available in a 10mbps speed and called 100based-T. Token Ring Token ring is a network technology introduced by IBM. It provides controlling hardware in a token ring network that transmits an electronic token for the nodes.  Explanation The controlling hardware in a token ring network transmits an electronic token (a small set of data) that travels around a ring of nodes in the form of the header. The reader contains control signals, including one specifying whether the token is free of carrying a message. A sender node captures a free token as it travels from node to node, changes it to "busy", add the message and set the address where the data should be sent. The token ring then contain around the ring and each computer along the way looks at the address until the token reaches the computer with the address that was recorded in the token. The receiving computer copies the contents of the token and sends an acknowledgement to the sending computer. When the sending computer receives the acknowledgement from the receiving computer, it resets the token state to "empty" and transmits it to the next computer in the ring. Page 91 of 157 VER: 04.

[Audio] Q12. What are the various communication software? Explain in detail. Communication Software Communication software consists of the programs that enable the host computer to establish, co-ordinate, monitor and control the flow of data through data communication system. Here are some of the tasks accomplished by such programs.  Data Sequencing It refers to breaking a long transmission into smaller blocks and maintaining control i.e. a long message is split up in to smaller packets. This technique is widely used in conjunction with error control techniques to reduce the amount of data that must be retransmitted in case of a detected error.  Data Routing Routing algorithms are designed to find the most efficient paths between sources and destinations. They can handle varying degrees of traffic on the present network configuration with optimal time utilization. Normally, they are dynamic enough to accommodate network changes and growth.  Flow Control Communication software also prevent a fast sender from overwhelming a slow receiver. It ensures resource sharing and protection against congestion by regulating the flow of data on the communication lines.  Error Control Data may be garbled or bits may be lost during transmission. It is essential to have programs that can determine if errors have occurred and cause the data to be retransmitted if necessary.  Co-Ordination Multiple Use Of Communication Lines When several terminals share communications channels to a computer, programs that co-ordinates data transmissions are needed. Posting is one technique for maintaining smooth flow of data to send. With another similar technique, called contention, "asked" if it has data to send. With another similar technique called contention, each terminal is instructed to "see" if any other terminal is transmitting and, if so, to wait.  Connection Establishment When two stations of a network want to communicate with each other, the communication software establishes and verifies a connection between the two.  Data Security Providing data security and privacy is called built into most communications software packages. It prevents access of data by unauthorized users because it is relatively easy to tap a data communications line.  Log Information Data communication software can also develop log information which consists of all jobs and data communication tasks that have taken place. Such information is normally used for financial purposes and the various users of the network are charged accordingly. Page 92 of 157 VER: 04.