Fundamentals of Computer 20CS11T Chapter 4.pdf

Vidya Vikas Educational Trust (R),
Vidya Vikas Polytechnic
27-128, Mysore - Bannur Road Alanahally,Alanahally Post, Mysuru, Karnataka 570028
Prepared by: Mr Thanmay J.S, H.O.D Mechanical Engineering VVETP, Mysore 58
Chapter 04: INTRODUCTION TO COMPUTER ORGANIZATION & OPERATING SYSTEM
4.1 Introduction
"Computer Organization and Operating System" is a fundamental area of study in computer science and
information technology. It encompasses two major aspects:
1. Computer Organization:
Computer organization refers to the physical components and their arrangement in a computer system.
It deals with how hardware components work together to execute instructions and manage data. Key
concepts in computer organization include:
• Central Processing Unit (CPU): The CPU is the heart of a computer. It executes instructions
stored in memory, performs arithmetic and logic operations, and manages the flow of data
within the system.
• Memory Hierarchy: This includes primary memory (RAM) and secondary storage (hard
drives, SSDs). Understanding how data is stored, accessed, and managed in memory is crucial.
• Input and Output Systems: This covers how data is input into the computer (e.g., through
keyboards and mice) and how it's output (e.g., displayed on a monitor or printed on a printer).
• Peripheral Devices: These are hardware components like graphics cards, network adapters,
and sound cards that extend the computer's functionality.
• Bus Architecture: Buses are pathways that allow data to move between CPU, memory, and
peripheral devices. Understanding bus architecture is essential for optimizing data transfer.
• Assembly Language: Knowledge of assembly language programming is often included in
computer organization. It's a low-level programming language that directly communicates with
the CPU.
2. Operating System:
An operating system (OS) is system software that manages hardware resources and provides essential
services to software applications. Key concepts in operating systems include:
• Process Management: The OS manages multiple processes (programs) running on the
computer, scheduling CPU time, and ensuring they don't interfere with each other.
• Memory Management: This involves allocating and deallocating memory space for
processes, ensuring efficient memory usage.
• File System: Operating systems provide a file system for organizing and storing data on
storage devices. This includes file creation, deletion, and access.

• Device Management: The OS controls and coordinates access to peripheral devices like
printers, keyboards, and monitors.
• User Interface: It provides a user-friendly interface, either through a command-line interface
(CLI) or a graphical user interface (GUI), allowing users to interact with the computer.
• Security and Access Control: OSs implement security measures to protect data and resources,
including user authentication and permission management.
• Networking: Many modern operating systems support networking features, enabling
computers to connect and communicate over networks.
• File and Data Backup: Some operating systems include backup and recovery tools to prevent
data loss.
Understanding both computer organization and operating systems is essential for anyone working with
computers, from software developers to IT professionals. These concepts provide the foundation for building
and optimizing computer systems and developing software that runs on them.
Overview of functional units of a computer
A computer is composed of several functional units, each with a specific role in the overall operation of the
system. These functional units work together to execute instructions and perform tasks. Here's an overview of
the primary functional units of a computer:
1. Central Processing Unit (CPU):
• The CPU is often referred to as the brain of the computer.
• It executes instructions stored in memory.
• It performs arithmetic and logic operations on data.
• The CPU consists of several components, including the Arithmetic Logic Unit (ALU) and the
Control Unit (CU).
2. Memory Unit:
• Memory is where data and instructions are stored for processing.
• It includes two main types:
• RAM (Random Access Memory): Provides fast, volatile storage for data and
programs currently in use.
• ROM (Read-Only Memory): Contains firmware and BIOS instructions that are
essential for booting the computer.
3. Input Unit:
• The input unit is responsible for receiving data and instructions from external sources.

• Input devices like keyboards, mice, scanners, and sensors are part of this unit.
4. Output Unit:
• The output unit is responsible for delivering processed data to external destinations.
• Output devices like monitors, printers, speakers, and display screens are part of this unit.
5. Control Unit (CU):
• The control unit manages and controls the operation of the CPU.
• It decodes instructions, coordinates data movement, and controls the flow of data between the
CPU and memory.
6. Arithmetic Logic Unit (ALU):
• The ALU performs arithmetic (addition, subtraction, multiplication, division) and logic
(comparison, AND, OR, NOT) operations.
• It is a critical component for data processing and calculation.
7. Cache Memory:
• Cache memory is a high-speed, small-sized memory located between the CPU and RAM.
• It stores frequently used data and instructions to improve processing speed.
8. Secondary Storage:
• Secondary storage devices, such as hard drives and solid-state drives, provide non-volatile
storage for long-term data retention.
9. I/O Controller:
• The I/O controller manages communication between the CPU and input/output devices.
• It ensures data is transferred between the CPU and peripherals efficiently.
10. Bus System:
• Buses are data pathways that allow communication between different functional units.
• There are various types of buses, including the data bus, address bus, and control bus.
11. Clock Unit:
• The clock unit generates clock signals that synchronize the operations of various components
in the computer.
12. Control Panel:
• In some computer systems, a control panel allows users to configure and manage hardware
settings.
These functional units work together in a coordinated manner to process data, execute programs, and perform
various computing tasks. Understanding how these units interact is essential for comprehending the inner
workings of a computer system and optimizing its performance.

Stored Program Concept
The Stored Program Concept is a fundamental concept in computer science and computer architecture.
It refers to the idea that both the instructions (program) and the data that the computer processes are stored in
the computer's memory in the same format. In other words, instructions for performing tasks and the data to
be processed are treated as the same type of information and can be manipulated by the central processing unit
(CPU) in a similar way. Key elements of the Stored Program Concept include:
1. Program Instructions: In a computer system, the instructions that define tasks to be executed are
stored in memory, just like any other data. These instructions are typically encoded in binary form or
a machine-readable format.
2. Data: Data that the program operates on, whether it's numbers, text, or any other form of information,
is also stored in memory. The CPU can read and manipulate this data based on the instructions
provided.
3. Uniformity: The Stored Program Concept treats program instructions and data as interchangeable
within the computer's memory. This uniformity allows for great flexibility and versatility in how the
computer processes information.
4. Sequential Execution: The CPU reads instructions from memory sequentially and executes them in
order. This sequential execution of instructions is the basis for the step-by-step processing that
computers perform.
5. Fetching and Executing: The CPU follows a fetch-decode-execute cycle, where it fetches an
instruction from memory, decodes it to determine the operation to be performed, executes the
operation, and then proceeds to the next instruction.
6. Program Control: The control unit of the CPU manages the flow of instructions, ensuring that the
program runs in the specified order.
7. Self-modifying Code: Since programs are stored in memory just like data, it's possible for a program
to modify its own instructions or the instructions of other programs. While this can be powerful, it can
also be a source of security vulnerabilities and errors.
The Stored Program Concept, often associated with the work of computer pioneers like John von Neumann,
is a fundamental principle that underlies the design of modern digital computers. It enables computers to be
programmable and versatile, as users can load different programs into memory to perform a wide range of
tasks without having to modify the hardware of the computer itself. This concept is a cornerstone of computer
architecture and has had a profound impact on the development and usability of computers.

Flynn's Classification of Computers
Flynn's Classification is a system used to categorize computer architectures based on the number of instruction
streams and data streams that can be processed concurrently. It was developed by Michael J. Flynn in 1966
and is often used to classify different types of computer systems, particularly in the context of parallel
computing. Flynn's Classification defines four basic categories:
1. Single Instruction, Single Data (SISD):
• In SISD computers, only one instruction stream (program) is executed at a time, and it operates
on a single data stream.
• This category is representative of traditional sequential or serial processing computers, where
one instruction is executed on one piece of data at a time.
• Examples of SISD computers include most conventional personal computers and workstations.
2. Single Instruction, Multiple Data (SIMD):
• SIMD computers execute a single instruction on multiple data streams concurrently.
• This is often associated with vector processing or array processing, where a single instruction
is applied to multiple elements of data simultaneously.
• SIMD architectures are common in graphics processing units (GPUs) and some specialized
scientific and engineering computing systems.
3. Multiple Instruction, Single Data (MISD):
• MISD computers are relatively rare and involve multiple instruction streams operating on a
single data stream.
• In practice, MISD architectures have limited applications and are not commonly used.
4. Multiple Instruction, Multiple Data (MIMD):
• MIMD computers have multiple instruction streams and multiple data streams, allowing for
the concurrent execution of different instructions on different data.
• MIMD architectures are typical of parallel computing systems, including multi-core
processors, cluster computing, and distributed computing.
• Each processing unit in a MIMD system can operate independently and execute its own set of
instructions on its own data.
Flynn's Classification provides a way to understand and categorize the parallelism and concurrency
capabilities of different computer architectures. It is particularly relevant in the field of high-performance
computing, where parallelism is used to tackle computationally intensive tasks. Depending on the application
and the nature of the problem to be solved, different categories within Flynn's Classification may be more
suitable for achieving optimal performance.

4.2 Memory Hierarchy
Memory hierarchy is a concept in computer architecture that refers to the organization and arrangement of
various types of computer memory, each with different characteristics, speeds, and storage capacities. The
primary purpose of a memory hierarchy is to bridge the speed gap between the fast, but limited, CPU registers
and cache memory, and the larger, slower, and less expensive main memory (RAM) and auxiliary memory
(secondary storage). Here's a brief explanation of the key components of the memory hierarchy:
1. Main Memory (RAM - Random Access Memory):
• Main memory, or RAM, is the primary volatile memory used by a computer to store data and
program instructions that are currently being used or processed.
• It is directly accessible by the CPU and provides fast data access speeds, but it is relatively
limited in capacity compared to secondary storage (hard drives, SSDs).
• Data in RAM is loaded from auxiliary storage (usually a hard drive or SSD) when a program
is executed and is essential for the computer's immediate operation.
2. Auxiliary Memory (Secondary Storage):
• Auxiliary memory, also known as secondary storage, includes storage devices like hard disk
drives (HDDs), solid-state drives (SSDs), optical drives (e.g., DVDs), and other non-volatile
storage media.
• It is used for long-term storage of data and programs that are not currently in use by the CPU.
• Data in auxiliary memory is non-volatile, meaning it retains its contents even when the
computer is powered off.
• Accessing data from auxiliary memory is significantly slower than accessing data from RAM
due to the mechanical nature of HDDs or the flash memory technology in SSDs.
3. Cache Memory:
• Cache memory is a small, high-speed volatile memory located between the CPU and main
memory.
• Its purpose is to store frequently accessed data and instructions from main memory to accelerate
the CPU's access times.
• Cache memory operates on the principle of spatial and temporal locality, meaning it stores data
that is likely to be used again in the near future.
• There are typically multiple levels of cache, including L1, L2, and sometimes L3 caches, with
each level having different capacities and proximity to the CPU.
• The closer the cache is to the CPU, the faster it can provide data, but it is also smaller in size.
In summary, the memory hierarchy is designed to optimize the balance between speed, capacity, and cost.
CPU registers and cache memory offer fast access but have limited capacity. Main memory (RAM) provides

a larger storage area but is slower than cache. Auxiliary memory (secondary storage) offers the largest capacity
but is the slowest in terms of data access. The hierarchical organization allows the computer to efficiently
manage data movement between these different levels of memory to ensure that the CPU operates as
efficiently as possible.
4.3 Introduction to BIOS and UEFI
BIOS (Basic Input/Output System) and UEFI (Unified Extensible Firmware Interface) are two firmware
technologies used in computers to initialize hardware components and boot the operating system. They serve
as an essential bridge between the hardware and software of a computer system. Here's an introduction to both
BIOS and UEFI:
BIOS (Basic Input/Output System):
1. Introduction:
• BIOS is a legacy firmware technology that has been in use since the early days of personal
computing.
• It is stored in a read-only memory (ROM) chip on the computer's motherboard.
• The primary purpose of BIOS is to perform the initial hardware checks and initialization when
the computer is powered on or restarted. This process is known as the POST (Power-On Self-
Test).
• BIOS also provides a basic set of functions and routines for hardware interaction, such as
keyboard input, display output, and disk I/O.
2. Features:
• BIOS has a text-based user interface, typically accessed by pressing a specific key (e.g., Del,
F2) during startup. This interface allows users to configure hardware settings.
• It stores the boot process instructions in the Master Boot Record (MBR) of the boot device,
such as a hard drive.
• BIOS has limitations, including a 16-bit architecture, a limited ability to boot from modern
storage devices like SSDs, and a lack of advanced security features.
3. Legacy Considerations:
• BIOS is considered legacy technology and is gradually being replaced by UEFI in modern
computers.
• Legacy BIOS systems often have compatibility modes (Legacy mode) to support older
operating systems and software.
UEFI (Unified Extensible Firmware Interface):
1. Introduction:
• UEFI is a more modern and flexible firmware standard that aims to replace BIOS.

• It is also stored in firmware chips on the motherboard but uses a different architecture and
approach compared to BIOS.
• UEFI is designed to provide a richer and more capable pre-boot environment for modern
computing needs.
2. Features:
• UEFI offers a graphical user interface (GUI) and a more user-friendly interface for configuring
hardware settings and diagnostics.
• It supports 64-bit architecture, enabling compatibility with modern hardware and storage
devices.
• UEFI can boot from larger and more complex storage systems, including GPT (GUID Partition
Table) disks, which BIOS cannot natively handle.
• Security features like Secure Boot are integral to UEFI, helping prevent the loading of
unauthorized or malicious code during the boot process.
• UEFI supports network booting, which allows computers to boot over a network connection.
3. Compatibility:
• UEFI systems often include a Compatibility Support Module (CSM) to run legacy BIOS-based
software, ensuring backward compatibility.
• Some operating systems, especially older ones, may require UEFI settings to be configured
appropriately for compatibility.
In summary, BIOS is the older and simpler firmware technology that has been widely used in traditional PCs.
UEFI is a more advanced and versatile replacement that offers improved functionality, better security, and
compatibility with modern hardware and storage devices. Most new computers come with UEFI firmware,
but many include backward compatibility with BIOS to support legacy systems and software.
4.4 OS Concepts
Operating System (OS) concepts are fundamental principles and components that form the basis of how an
operating system functions and interacts with computer hardware and software. Understanding these concepts
is essential for anyone working with or studying operating systems. Here are some key OS concepts:
1. Process Management:
• A process is a program in execution. The OS manages processes, scheduling CPU time,
creating and terminating processes, and ensuring they don't interfere with each other.
• Concepts include process states (e.g., running, ready, blocked), context switching, and inter-
process communication (IPC).

2. Memory Management:
• Memory management involves allocating and deallocating memory space for processes,
ensuring efficient memory usage, and preventing memory leaks.
• Concepts include virtual memory, paging, segmentation, and memory protection.
3. File System:
• The OS provides a file system for organizing and storing data on storage devices. It includes
file creation, deletion, access, and protection.
• Concepts include directories, file attributes, file permissions, and file systems (e.g., FAT,
NTFS, ext4).
4. Device Management:
• The OS controls and coordinates access to peripheral devices like printers, keyboards, and
network adapters.
• Concepts include device drivers, device I/O, and interrupt handling.
5. User Interface:
• The OS provides a user-friendly interface for users to interact with the computer. This can be
a command-line interface (CLI) or a graphical user interface (GUI).
• Concepts include shells (CLI), desktop environments (GUI), and user authentication.
6. Concurrency and Parallelism:
• OSes manage multiple processes and threads concurrently. Concepts include synchronization,
deadlock prevention, and parallel processing.
7. Networking:
• Many modern OSes support networking features, allowing computers to connect and
communicate over networks.
• Concepts include network protocols (e.g., TCP/IP), sockets, and network stack.
8. Security and Access Control:
• OSes implement security measures to protect data and resources, including user authentication,
access control lists (ACLs), and encryption.
9. File and Data Backup:
• Some OSes include backup and recovery tools to prevent data loss and ensure data integrity.
10. System Calls:
• System calls are functions provided by the OS that allow programs to request services from the
kernel. These include functions like file operations, process management, and I/O operations.
11. Shell and Command Line Interface (CLI):
• The shell is a program that provides a text-based interface for interacting with the OS. Users
can execute commands and scripts through the CLI.

12. Virtualization:
• OS virtualization allows multiple operating systems or instances to run on a single physical
machine. This is essential for server consolidation and cloud computing.
13. Fault Tolerance and Recovery:
• OSes may have mechanisms to detect and recover from hardware or software failures to ensure
system reliability.
14. Real-Time Operating Systems (RTOS):
• RTOSes are specialized OSes designed for systems with strict timing and response
requirements, such as embedded systems and industrial control.
15. Distributed Systems:
• Some OS concepts extend to distributed systems, where multiple computers work together to
perform a task, often connected over a network.
These OS concepts provide a foundation for understanding how operating systems manage hardware and
software resources, provide a user-friendly interface, and ensure the efficient and secure operation of computer
systems. They are applicable in various computing environments, from personal computers to servers and
embedded systems.
Types of OS (Batch Operating System, Multitasking/Time Sharing OS, Multiprocessing OS, Real Time
OS, Distributed OS, Network OS, Mobile OS)
Operating systems (OS) come in various types, each designed for specific purposes and computing
environments. Here is an overview of different types of operating systems:
1. Batch Operating System:
• Purpose: Batch operating systems are designed for batch processing, where a series of jobs
(programs) are submitted to the system to be executed without user intervention.
• Characteristic: They process jobs in batches, one after the other, without real-time interaction.
2. Multitasking/Time Sharing OS:
• Purpose: These OSes allow multiple tasks or processes to run concurrently, sharing the CPU's
time. Users can interact with the computer in a time-shared manner.
• Characteristic: They provide the illusion of parallel execution by rapidly switching between
tasks, making it appear as if multiple programs are running simultaneously.
3. Multiprocessing OS:
• Purpose: Multiprocessing OSes are designed to take advantage of multiple CPUs or processor
cores to execute tasks in parallel.

• Characteristic: They distribute tasks across multiple processors to improve performance and
throughput.
4. Real-Time OS (RTOS):
• Purpose: RTOSes are designed for systems with strict timing requirements, where tasks must
be completed within predefined time constraints. Common in embedded systems and control
systems.
• Characteristic: They provide deterministic response times, ensuring that critical tasks are
executed without delay.
5. Distributed OS:
• Purpose: Distributed OSes manage and coordinate the execution of tasks across multiple
interconnected computers or nodes in a network.
• Characteristic: They enable distributed computing, where resources and tasks are distributed
across the network for improved scalability and fault tolerance.
6. Network OS:
• Purpose: Network OSes provide network-specific functionalities and services for managing
network resources, sharing files, and enabling communication between devices.
• Characteristic: They facilitate network operations and ensure efficient data transfer and
access.
7. Mobile OS:
• Purpose: Mobile OSes are designed for smartphones, tablets, and other mobile devices. They
provide a user-friendly interface and manage hardware and software resources efficiently.
• Characteristic: Mobile OSes are optimized for touchscreens, support app ecosystems, and
offer features like power management and connectivity.
8. Single-User OS:
• Purpose: Single-user OSes are designed for personal computers and workstations, where a
single user interacts with the system at a time.
• Characteristic: They provide a user-friendly interface and manage hardware and software
resources for individual users.
9. Multi-User OS:
• Purpose: Multi-user OSes are designed for servers and mainframes, allowing multiple users
to simultaneously access and use the system's resources.
• Characteristic: They provide user authentication, access control, and resource sharing among
multiple users.

10. Embedded OS:
• Purpose: Embedded OSes are tailored for specific embedded systems and devices, such as
automotive systems, medical devices, and IoT devices.
• Characteristic: They are often lightweight, real-time, and optimized for the specific hardware
they run on.
These different types of operating systems cater to a wide range of computing needs, from personal computing
to industrial control systems, mobile devices, and large-scale distributed networks. The choice of an OS
depends on the specific requirements of the application or environment in which it will be used.
Services of OS
Operating systems (OS) provide a wide range of services to manage hardware and software resources,
facilitate user interaction, and ensure the efficient operation of a computer system. These services help abstract
hardware complexities and provide a consistent environment for running applications. Here are some of the
essential services provided by an operating system:
1. Program Execution:
- The OS loads programs into memory and schedules them for execution on the CPU. It manages the
execution of multiple programs concurrently through process management.
2. I/O Operations:
- The OS handles input and output operations, allowing programs to read from and write to devices like
keyboards, disks, displays, and network interfaces.
3. File System Manipulation:
- It provides file-related services, including file creation, deletion, reading, writing, and organization within
directories.
4. Error Handling:
- The OS detects and manages hardware and software errors, providing error messages, logging errors, and
taking appropriate actions to prevent system crashes.
5. Security and Access Control:
- It enforces user authentication and access control to protect data and system resources from unauthorized
access. This includes user account management and permission systems.

6. Resource Allocation:
- The OS allocates system resources (CPU time, memory, devices) to different processes or tasks to ensure
fair and efficient resource utilization.
7. Task Scheduling:
- The OS schedules processes and threads to execute on the CPU, employing various scheduling algorithms
to optimize system performance and responsiveness.
8. Memory Management:
- It manages physical and virtual memory, including allocation, deallocation, and protection, to ensure
efficient use of available memory resources.
9. Networking:
- In networked environments, the OS provides networking services, including protocol implementation,
socket management, and network device control.
10. User Interface:
- For interactive systems, the OS provides a user interface (either command-line or graphical) for user
interaction, including the management of windows, icons, and menus.
11. Time and Date Management:
- The OS maintains system time and date, and it can synchronize with external time servers for accurate
timekeeping.
12. Device Management:
- It manages and controls peripheral devices such as printers, scanners, and external storage devices,
ensuring proper communication and resource allocation.
13. Backup and Recovery:
- Some OSes include backup and recovery utilities to safeguard data and restore the system to a previous
state in case of failures.
14. Power Management:
- Modern OSes support power-saving features to optimize energy consumption in portable devices and
desktop computers.

15. Virtualization:
- In virtualized environments, the OS provides services for creating, managing, and running virtual
machines (VMs) on physical hardware.
16. Distributed Computing:
- In distributed systems, the OS offers services for communication, process coordination, and resource
sharing among networked nodes.
These services collectively enable users to run applications, manage data, interact with hardware, and ensure
the stable and secure operation of the computer system. The specific services offered by an OS may vary
depending on the OS type and its intended use.

Previous Year Question Papers
April / May 2021
SECTION-IV
7. (a) Explain Computer network categories. 05
(b) Describe online data processing method. 05
(c) Explain the functional units of computer with diagram. 10
8. (a) Discuss Auxiliary memory. 05
(b) Explain Cache memory. 05
(c) Classify Computers based on Flynn's classification. 05
(d) Explain BIOS. 05
April / May 2022
SECTION-IV
7. (a) In distribution data processing, how data is arranged & processed? 05
(b) Explain functional units of computer with neat block diagram. 10
(c) Classify the following memory as Primary/Secondary: 05
(i) ROM
(ii) SRAM
(iii) DRAM
(iv) HDD
(v) CD-R
(vi) DVD
8. (a) Explain any 2 cyber securities threats. 05
(b) Draw the memory hierarchy and label it. 05
(c) List and explain the services of OS (Operating System). 10
Oct / Nov 2021
SECTION-IV
7. (a) Explain the following: 10
(i) Single user programming
(ii) Multi programming
(b) List and explain Flynn's classification of computers. 05
(c) Briefly explain BIOS. 05
8. (a) Explain memory hierarchy with a diagram. 4+6
(b) Describe the functions of
(i)Real time operating system 05
(ii) Mobile operating system 05
June /July 2023
SECTION-IV
7. (a) Define Computer Network. Explain categories of network. 10
(b) Explain the functional units of computer with a neat diagram. 10
8. (a) Write a note on: 10
(i) Primary Memory
(ii) Cache Memory
(b) Define Operating System. Explain any two types of Operating System. 10

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