Computer System - Class 11 Computer Science - Chapter 1 - Notes, NCERT Solutions & AI Assistant
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Notes - Computer System | Class 11 NCERT | Computer Science
Comprehensive Class 11 Notes: Understanding the Computer System
Introduction
Computers have become an integral part of our lives, and understanding their functioning is crucial. This guide is tailored for Class 11 students to grasp the fundamentals of a computer system, its components, and their roles.
Components of a Computer System
Primary Components of a Computer System
Central Processing Unit (CPU)
Often referred to as the brain of the computer, the CPU is responsible for executing instructions. It consists of two main units:
- Arithmetic Logic Unit (ALU): Performs arithmetic and logical operations.
- Control Unit (CU): Directs the operations of the CPU and manages data flow within the computer.
Memory Types and Functions
Memory is essential for storing data and instructions. It is classified into:
-
Primary Memory:
- RAM (Random Access Memory): Volatile memory used for temporary storage.
- ROM (Read-Only Memory): Non-volatile memory used for permanent storage of critical data.
- Secondary Memory: Used for long-term storage, including hard drives and SSDs.
Input Devices
Input devices allow users to interact with the computer by providing data and instructions. Examples include the keyboard, mouse, scanner, and touch screen.
Output Devices
Output devices convert digital information into human-readable form. Common examples are monitors, printers, and speakers.
Data Transfer in a Computer System
How Data Transfers Between CPU and Memory
Data transfer in a computer system occurs through physical wires called buses. These buses are classified into:
- Data Bus: Transfers actual data.
- Address Bus: Carries memory addresses.
- Control Bus: Transmits control signals.
The collective term for these buses is the system bus.
Evolution and Microprocessors
Evolution of Computer Systems
Computing devices have evolved significantly over time, from mechanical calculators like the Pascaline to modern-day computers. This journey includes key milestones:
Microprocessors
A microprocessor is a CPU on a single chip, responsible for executing instructions. Modern microprocessors are highly efficient and can perform millions of instructions per second.
Memory in Detail
Computer Memory Explained
Memory in a computer system is used to store data temporarily or permanently.
Units of Memory
Memory is measured in bytes, and larger units include kilobytes (KB), megabytes (MB), gigabytes (GB), and so on.
Cache Memory
Cache memory is a high-speed memory located between the CPU and RAM to speed up data access.
Comparing RAM and ROM
- RAM: Volatile, used for temporary storage during processing.
- ROM: Non-volatile, used for permanent storage of essential data like the bootloader.
Software in a Computer System
Software Essentials
Software consists of instructions that make hardware functional.
System Software
System software provides basic functionality to operate the computer.
- Operating Systems: Manage hardware and software resources.
- System Utilities: Maintenance and configuration tools.
- Device Drivers: Interface between the operating system and hardware devices.
Programming Tools and Languages
Programming languages allow developers to write instructions for the computer. These languages are translated into machine code using translators like compilers and interpreters.
Application Software
Application software performs specific tasks for users, such as word processing, web browsing, and gaming.
Data and Information
Understanding Data and Information
Data can be classified into:
- Structured Data: Organised in a predefined format, like tables.
- Unstructured Data: Lacks a specific format, like text documents.
- Semi-structured Data: Contains tags to separate data elements, like HTML files.
Operating Systems and User Interfaces
Functions of an Operating System
An operating system manages computer resources, including process management, memory management, file management, and device management.
Types of User Interfaces
- Command-Based Interface: Requires typing commands.
- Graphical User Interface (GUI): Uses icons and menus.
- Touch-Based Interface: Allows interaction via touchscreens.
- Voice-Based Interface: Uses voice commands.
- Gesture-Based Interface: Interprets gestures for commands.
Security and Data Management
Security Concerns in Computer Systems
Data security is vital. Common concerns include data deletion, data recovery, and protection against unauthorised access. Measures such as encryption and access controls help safeguard data integrity.
Conclusion
Understanding the components and functionalities of a computer system is essential for effectively utilising its capabilities. This guide provides a foundational knowledge that will aid in deeper exploration and learning in the field of computer science.
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Extra Questions - Computer System | NCERT | Computer Science | Class 11
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Name the software required to make a computer functional. Write down its two primary services.
The software required to make a computer functional is the Operating System (OS).
Two Primary Services:
Process Management:
Resource Allocation: Manages multiple processes and allocates CPU time to each process.
Process Coordination: Ensures processes are executed in the most efficient manner with minimum interference.
Memory Management:
Memory Allocation and Deallocation: Dynamically allocates memory to processes and reclaims it when not in use.
Memory Protection: Ensures that processes do not interfere with each other’s memory and provides secure access.
These services are essential for the optimal functioning and security of the computer system.
How does the computer understand a program written in high level language?
Computer programs written in high-level languages are not directly understood by computers, which process data in machine language (binary code - 0s and 1s). Therefore, a translation process is required to convert high-level language code into machine language. This is accomplished through language translators, which can be categorized into three main types:
Assembler: Converts code written in assembly language into machine language. Each assembler is specific to a particular microprocessor instruction set.
Compiler: Converts the entire source code (high-level language code) into machine code at once. If the code is error-free, it is then executed by the computer. After compilation, the compiler is not needed for the further execution of the program.
Interpreter: Translates one line at a time from high-level language to machine language and executes it immediately. This type of translator continuously converts each line every time the program is run.
Summary of steps:
Write the code in a high-level language (source code).
Use a translator (compiler or interpreter) to convert the source code to machine code (object code).
The computer executes the machine code instructions to perform the desired tasks.
This translation process is vital to make high-level programming languages usable, allowing developers to write complex programs efficiently without dealing directly with machine language.
Why is the execution time of the machine code less than that of source code?
The execution time of machine code is less than that of source code because:
No Translation Overhead: Machine code is already in a format that the CPU can directly execute, whereas source code needs to be translated into machine code through a process called compilation or interpretation every time it is run.
Optimized for Hardware: Machine code is optimized for the specific hardware it runs on, ensuring efficient execution. In contrast, source code needs additional processing to be understood by the hardware.
Reduced Complexity: Executing machine code involves straightforward, low-level operations that the CPU can perform rapidly without additional interpretation or compilation steps.
Source code, on the other hand, requires translation into machine code before it can be executed, which introduces additional execution time. This translation can occur either at compile-time (which involves a compiler) or at run-time (which involves an interpreter).
What is the need of RAM? How does it differ from ROM?
RAM (Random Access Memory) and ROM (Read Only Memory) are both crucial components of a computer's primary memory, but they serve different purposes and have distinct characteristics.
Need of RAM
RAM is needed for the following reasons:
Temporary Storage: It stores data and instructions temporarily while the computer is executing tasks.
High Speed: RAM is much faster compared to secondary storage devices, allowing for quick data accessibility for the CPU.
Volatile Storage: It can be written to and read from multiple times which is vital for processing tasks and running applications.
Differences between RAM and ROM
Here are the key differences between RAM and ROM:
Volatility:
RAM is volatile. This means all data is lost when the computer is turned off.
ROM is non-volatile, meaning it retains its data even when the power is turned off.
Mutability:
RAM can be read from and written to. This characteristic is crucial for general processing tasks.
ROM can be read-only (or less frequently written to in some cases), making it ideal for storing immutable data like firmware.
Usage:
RAM is used for temporary storage of data that the CPU accesses while performing tasks.
ROM is used for permanent storage of data that is needed for booting and basic system functions, such as the startup program (boot loader).
Speed:
RAM is typically faster than ROM because it needs to be accessed rapidly by the CPU while executing instructions.
ROM is generally slower compared to RAM.
Storage Capacity:
Modern RAM sizes can go up to multiple gigabytes (GB), facilitating the operation of complex and multiple applications.
ROM usually comes in smaller sizes compared to RAM as it's only meant to store essential and immutable data.
In summary, while RAM is essential for temporary, high-speed data storage and frequent access during computer operations, ROM is crucial for permanently storing firmware and essential programs that are critical for system boot and basic functionality.
What is the need for secondary memory?
The need for secondary memory in a computer system arises due to several important factors:
Permanent Storage: Unlike primary memory (RAM), secondary memory is non-volatile, meaning it retains data even when the computer is turned off. This is crucial for storing data and programs permanently.
Larger Capacity: Secondary memory generally offers a much larger storage capacity compared to primary memory, allowing for the storage of extensive amounts of data, programs, and files.
Cost Effectiveness: Secondary storage devices, such as hard disk drives (HDDs) and solid-state drives (SSDs), are cheaper per unit of storage compared to RAM. This makes it economically viable to store large amounts of data.
Backup and Archiving: Secondary memory is essential for backing up important data and for archiving information that may not be needed frequently but must be preserved.
Indirect Access: While secondary memory is slower than primary memory, it provides a way to access data that does not need to be constantly moved in and out of the primary memory, thus optimizing the performance of the computer system.
Overall, secondary memory is indispensable for ensuring data persistence, providing ample storage space, and maintaining cost efficiency in computer systems.
How do different components of the computer communicate with each other?
Different components of the computer communicate with each other using physical wires called a bus. Here is a breakdown of how the communication occurs:
Types of Buses:
Data Bus: Transfers data between different components.
Address Bus: Transfers addresses between CPU and main memory. The CPU specifies the address of the memory location it wants to read or write from.
Control Bus: Communicates control signals between different components of a computer.
System Bus: All the above three buses collectively make the system bus, which facilitates data transfer between components such as the CPU, memory, and I/O devices.
In summary, data is transferred between the CPU and primary memory as well as between primary and secondary memory using the system bus. The CPU places the address on the address bus, data on the data bus, and the control signals on the control bus to perform read and write operations efficiently.
Draw the block diagram of a computer system. Briefly write about the functionality of each component.
Block Diagram of a Computer System
graph TD
A(Input Device) --> B["Central Processing Unit (CPU)"]
B --> C["Control Unit (CU)"]
B --> D["Arithmetic Logic Unit (ALU)"]
B --> E[Primary Memory]
E --> F[Secondary Storage Devices]
C <--> E
D <--> E
Components and their functionality:
Central Processing Unit (CPU):
Functionality:
Acts as the brain of the computer.
Executes instructions from programs by fetching data from memory.
Performs arithmetic and logic operations.
Stores interim data in registers within the CPU.
Contains key components like the Arithmetic Logic Unit (ALU), which handles all arithmetic and logical operations, and the Control Unit (CU), which manages the execution sequence and data flow.
Memory:
Functionality:
Stores data and program instructions temporarily.
RAM (Random Access Memory) is volatile and provides temporary storage.
ROM (Read-Only Memory) is non-volatile and holds critical non-changing data, like the boot loader.
Input Devices:
Functionality:
Allow data and control signals to be input into the computer.
Examples include keyboard, mouse, scanner, and touch screen.
Output Devices:
Functionality:
Convert digital data from the computer into human-understandable form.
Examples include monitor, printer, projector, and speakers.
Storage Devices:
Functionality:
Provide permanent storage for data and instructions.
Examples include Hard Disk Drive (HDD), Solid State Drive (SSD), DVDs, and USB flash drives.
In summary, each component of a computer system has a specific role that interconnects with others to process, store, and display data efficiently.
What is the primary role of system bus? Why is data bus is bidirectional while address bus is unidirectional?
The primary role of the system bus is to transfer data, addresses, and control signals between the components of a computer system. It acts as a communication pathway for data exchange among the CPU, memory, and I/O devices.
Data Bus and Address Bus:
Data Bus:
The data bus is bidirectional because data must flow in both directions:
From the CPU to memory or I/O devices (e.g., storing data).
From memory or I/O devices to the CPU (e.g., reading data).
Address Bus:
The address bus is unidirectional because it only needs to carry addresses from the CPU to memory or I/O devices:
The CPU places the address of the data it wishes to read or write on the address bus, specifying the location to access.
Differentiate between proprietary software and freeware software. Name two software for each type.
Proprietary Software
Proprietary software is software that is owned by an individual or a company (usually the one that developed it). The owner retains exclusive rights to the use, modification, and distribution of the software. Users must purchase a license to use it.
Examples: Microsoft Windows, Tally
Freeware Software
Freeware software is software that is available free of charge. Users can download, install, and use the software without paying any fees. However, the source code is usually not available, and users cannot modify or redistribute it.
Examples: Skype, Adobe Reader
Write the main difference between microcontroller and microprocessor. Why do smart home appliances have a microcontroller instead of microprocessor embedded in them?
The main difference between a microcontroller and a microprocessor is:
Microprocessor:
It contains only a CPU on a single chip.
It needs external components like RAM, ROM, and other peripherals for functioning.
It is designed for general purpose tasks where the operations might change dynamically.
Microcontroller:
It has a CPU, RAM, ROM, and other peripherals embedded on a single chip.
It is designed for specific tasks and has low power consumption.
Why Smart Home Appliances Use Microcontrollers Instead of Microprocessors:
Specific Tasks: Smart home appliances typically perform specific and predefined tasks, such as controlling temperature, humidity, or lights. Microcontrollers are ideal for these focused, repetitive activities.
Cost and Size: Microcontrollers are generally smaller and less expensive compared to microprocessors. This makes them suitable for embedding in various appliances without increasing the cost or size significantly.
Integrated Peripherals: Microcontrollers come with integrated peripherals (like ADC, timers, GPIOs) which are essential for direct control and management of sensors and actuators in smart appliances.
Power Efficiency: Microcontrollers are designed to be power-efficient, which is critical for smart home devices that need to operate continually on low power.
Thus, a microcontroller is a better fit for smart home appliances due to the integration, efficiency, and specificity of their tasks.
Mention the different types of data that you deal with while browsing the Internet.
While browsing the Internet, you typically deal with three different types of data:
Structured Data: This includes data that is highly organized and easily searchable in databases. Examples are transactions, user profiles, or form submissions.
Unstructured Data: This data lacks a specific format or structure. Examples include emails, social media posts, videos, images, and web pages.
Semi-structured Data: This data does not have a formal structure but includes tags or markers to separate elements. Examples are JSON or XML documents, and HTML web pages.
Each of these data types plays a crucial role in how information is processed and presented on the Internet.
Categorise the following data as structured, semi structured and unstructured:
Newspaper
Cricket Match Score
HTML Page
Patient records in a hospital
Here is the categorisation of the given data:
Newspaper: Unstructured Data
Cricket Match Score: Structured Data
HTML Page: Semi-structured Data
Patient records in a hospital: Structured Data
In summary, newspaper data contains text and images without a pre-defined format making it unstructured. Cricket match scores and patient records are well-organized in a tabular format which makes them structured data. HTML pages use tags to define elements, making them semi-structured data.
Name the input or output device used to do the following:
a) To output audio
b) To enter textual data
c) To make hard copy of a text file
d) To display the data or information
e) To enter audio-based command
f) To build 3D models
g) To assist a visually-impaired individual in entering data
a) To output audio: Speaker or Headphone
b) To enter textual data: Keyboard
c) To make hard copy of a text file: Printer
d) To display the data or information: Monitor or Projector
e) To enter audio-based command: Microphone
f) To build 3D models: 3D Printer
g) To assist a visually-impaired individual in entering data: Braille Keyboard
Each device plays a crucial role in interacting with the computer system effectively.
Identify the category (system, application, programming tool) of the following software:
a) Compiler
b) Assembler
c) Ubuntu
d) Text editor
Based on the information provided in the chapter:
a) Compiler
Category: Programming tool
b) Assembler
Category: Programming tool
c) Ubuntu
Category: System software (specifically, an operating system)
d) Text editor
Category: Programming tool
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