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Notes On Python- Std 11Book Chapter 1 Computer Fundamentals

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  1. COMPUTER SCIENCE (Python Book - Std 11) [Chapter 1]
  2. Unit -1 COMPUTER FUNDAMENTALS 1. Name at least four early calculating devices? Abacus • Napier's Logs and Bones Pascaline Leibnitz's Calculator 2. Name the first operational general purpose computer? Mark 1 is the machine used to multiply two 10 digit numbers in 5 seconds. This is the first operational general purpose computer which is based on the concept of Babbage's Analytical engine. 3. Who first proposed the concept of 'Stored Program Computer'? In 1945, Dr. John Von Neumann proposed the concept of a stored program computer. 4. Define the IPO cycle? IPO Cycle needs certain input, processes that input and produces the desired output. The input unit takes the input, the central processing unit does the processing of data and the output unit produces the output. The memory unit holds the data and instructions during the processing. Every task given to a computer follows an Input- Process- Output Cycle (IPO cycle). 5. Differentiate between data and information? Data: Data is the term used for raw facts and figures. For example, 134, + 9, 'Raju', 'C' are data. Information: Data represented in useful and meaningful form is information. In simple words we can say that data is the raw material that is processed to give meaningful, ordered or structured information.
  3. For example, Raju is 9 years old. This is information about Raju and conveys some meaning. 6. Explain the Von Neumann Computer? In 1945, Dr. John Von Neumann proposed the concept of a stored program computer. As per this concept the program and data could be stored in the same memory unit. Communication Program + Data Channel Processor Storage (Memory) According to Von Neumann architecture, the processor executes instructions stored in the memory of the computer. The processor at a time can either fetch data or an instruction because there is only one communication channel. That is at one point of time either the data or an instruction can be picked (fetched) from the storage unit for execution by the processor. So the execution takes place in sequential manner. This limitation of Von Neumann Computer is known as Von Neumann bottleneck. EDVAC (Electronic Discrete Variable Automatic Computer) was the first stored program computer developed in 1952. After the invention of first electronic computer ENIAC(Electronic Numerical Integrator and Calculator) in 1 946, the computer technology improved tremendously and at very fast pace.
  4. 7. Compare the salient features of first and second generation computers? Features of First Generation Computers: Used vacuum tubes to control and amplify electronic signals Huge computers that occupied lot of space High electricity consumption and high heat generation Were unreliable since they were prone to frequent hardware failures Commercial production was difficult They were very costly and required constant maintenance Continuous air conditioning was required Programming was done in machine language although assembly language also started at the end of this generation Example : ENIAC , EDVAC UNIVAC 1 Features of Second Generation Computers: Use transistor based technology Were smaller and less expensive as compared to first generation Consumed less electricity and emitted less heat Magnetic core memories and magnetic disks were used as primary and secondary storage respectively First operating system developed Programming in assembly language and in the later part high level languages were used Wider commercial use but commercial production was still difficult They also required constant air-conditioning. Examples: IBM 1401, IBM 1620, UNIVAC 1108
  5. 8. Why is Charles Babbage known as the Father of Modern Computers? The great inventions of Charles Babbage earned him the title of 'Father of Modern Computers'. In 1822 Charles Babbage developed a machine called 'Difference Engine' which is used to calculate mathematical functions, polynomial evaluations and solve differential equations. In 1833 he designed Analytical engine which proved to be the basis of modern computer. This machine will perform all four arithmetic operations as well as comparison. It included the concept of central processor, memory storage and input-output devices. 9. Explain the functional components of a computer with the help of a block diagram. Functional Components of a Computer: Every task given to a computer follows an Input- Process- Output Cycle (IPO cycle). It needs certain input, processes that input and produces the desired output. The input unit takes the input, the central processing unit does the processing of data and the output unit produces the output. The memory unit holds the data and instructions during the processing. Block Diagram of Functional components of a computer Output Unit CPU Memory Input Unit Registers
  6. Input Unit The input unit consists of input devices that are attached to the computer. These devices take input and convert it into binary language that the computer understands. Some of the common input devices are keyboard, mouse, joystick, scanner etc. Central Processing Unit (CPU) Once the information is entered into the computer by the input device, the processor processes it. The CPU is called the brain of the computer because it is the control centre of the computer. As the CPU is located on a small chip, it is also called the microprocessor. It first fetches instructions from memory and then interprets them so as to know what is to be done. If required, data is fetched from memory or input device. Thereafter CPU executes or performs the required computation and then either stores the output or displays on the output device. The CPU has three main components which are responsible for different functions — Arithmetic Logic Unit (ALU) , Control Unit (CU) and Memory registers. Arithmetic and Logic Unit (ALU) The ALU performs mathematical calculations and takes logical decisions. Arithmetic calculations include addition, subtraction, multiplication and division. Logical decisions involve comparison of two data items to see which one is larger or smaller or equal. Control Unit The Control unit coordinates and controls the data flow in and out of CPU and also controls all the operations of ALU, memory registers and also input/output units. It is also responsible for carrying out all the instructions stored in the program.
  7. It decodes the fetched instruction, interprets (understands) it and sends control signals to input/output devices until the required operation is done properly by ALU and memory. Memory Registers A register is a temporary unit of memory in the CPU. These receive data/information and then this data/information is held in them as per the requirement. Registers can be of different sizes(16 bit , 32 bit , 64 bit and so on) and each register inside the CPU has a 14 specific function like storing data, storing an instruction, storing address of a location in memory etc. The user registers can be used by an assembly language programmer for storing operands, intermediate results etc. Accumulator (ACC) is the main register in the ALU and contains one of the operands of an operation to be performed in the ALI-J. Memory Memory attached to the CPU is used for storage of data and instructions and is called internal memory. During processing, it is the internal memory that holds the data. The internal memory is divided into many storage locations, each of which can store data or instructions. Each memory location is of the same size and has an address. With the help of the address, the computer can find any data easily without having to search the entire memory. The internal memory is also called the Primary memory or Main memory. When the task is performed, the CU makes the space available for storing data and instructions, thereafter the memory is cleared and the memory space is then available for the next task. The time of access of data is independent of its location in the memory therefore this memory is also called Random Access memory (RAM). Primary memory is volatile in nature. That means when the power is switched off, the data stored in this memory is permanently erased. That is why secondary memory is needed to store data and information permanently for later use.
  8. Some of the examples of secondary storage devices are hard disk, compact disks, pen drives etc. Output Unit The output unit consists of output devices that are attached with the computer. It converts the binary data coming from CPU to human understandable from. The common output devices are monitor, printer, plotter etc. 10. What are the functions of the control unit? The functions of the control unit are The Control unit coordinates and controls the data flow in and out of CPU and also controls all the operations of ALU, memory registers and also input/output units. It is also responsible for carrying out all the instructions stored in the program. It decodes the fetched instruction, interprets (understands) it and sends control signals to input/output devices until the required operation is done properly by ALU and memory. 11. Where are the instructions needed to start a computer stored? The instructions are needed in the memory of computer and the processor executes it according to the Von New Mann Computer which is based on the concept of stored program computer. There is only one communication channel, the processor at a time can either fetch data or an instruction. That means at one point of time either the data or an instruction can be picked (fetched) from the storage unit for execution by the processor. Hence execution takes place in sequential manner EDVAC(Electronic Discrete Variable Automatic Computer) was the first stored program computer developed in 1952.
  9. Instructions stored in a computer: The computer does its primary work in a part of the machine we cannot see, a control center that converts data input to information output. This control center, called the central processing unit (CPU), is a highly complex, extensive set of electronic circuitry that executes stored program instructions. 12. Explain booting process and its types. When the computer is switched on, a copy of boot program is brought from ROM into the main memory. This process is called booting The CPU first runs a jump instruction that transfers to BIOS (Basic Input output System) and it starts executing. The BIOS conducts a series of self diagnostic tests called POST (Power On Self Test). These tests include memory tests, configuring and starting video circuitry, configuring the system's hardware and checking other devices that help to function the computer properly. Thereafter the BIOS locates a bootable drive to load the boot sector The execution is then transferred to the Boot Strap Loader program on the boot sector which loads and executes the operating system. If the boot sector is on the hard drive then it will have a Master Boot record (MBR) which checks the partition table for active partition. If found, the MBR loads that partition's boot sector and executes it. Booting Process is of two types — Warm and Cold Cold Booting and Warm booting Cold Booting: When the system starts from initial state i.e. it is switched on, we call it cold booting or Hard Booting. When the user presses the Power button, the instructions are read from the ROM to initiate the booting process. Warm Booting: When the system restarts or when Reset button is pressed, we call it Warm Booting or Soft Booting. The system does not start from initial state and so all diagnostic tests need not be carried out in this case. There are chances of data loss and system damage as the data might not have been stored properly.
  10. 13. Differentiate between : Digital computers and Analog computers Microcomputers and Mini Computers Digital computers and Analog computers Digital Computers: Digital computers are capable of processing information in discrete form. In digital technology data which can be in the form of letters, symbols or numbers is represented in binary form i.e. Os and Is. Binary digits are easily expressed in a digital computer by the presence (1) or absence (0) of current or voltage. It computes by counting and adding operations. The digital computers are used in industrial, business and scientific applications. They are quite suitable for large volume data processing. Analog Computers: An analog computer works on continuously changeable aspects of physical phenomenon such as fluid pressure, mechanical motion and electrical quantities. These computers measure changes in continuous physical quantities say current and voltage. These computers are used to process data generated by ongoing physical processes. A thermometer is an example of an analog computer since it measures the change in mercury level continuously. Although the accuracy of an analog computer is less as compared to digital computers, yet it is used to process data generated by changing physical quantities especially when the response to change is fast. Most present day analog computers are well suited to simulating systems. A simulator helps to conduct experiments repeatedly in real time environment. Some of the common examples are simulations in aircrafts, nuclear power plants, hydraulic and electronic networks. Micro computers and Mini computers Micro Computers: These are also known as Personal Computers. These type of digital computer uses a microprocessor (a CPU on a single chip) and include both desktops and laptops.
  11. These computers can work on small volume of data, are very versatile and can handle variety of applications. These computers are being used as work stations, CAD, multimedia and advertising applications. Small portable computers such as PDAs (Personal Digital Assistants) and tablets with wireless computing technology are increasingly becoming popular. Mini Computers: These computers can support multiple users working simultaneously on the same machine. These are mainly used in an organization where computers installed in various departments are interconnected. These computers are useful for small business organizations.

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