Operating System Concepts by Ekta Walia: Why You Should Read this Book and How to Get it for Free
Operating System Concepts by Ekta Walia Free: A Comprehensive Guide
If you are interested in learning about the fundamentals and applications of operating systems, you might have come across the book Operating System Concepts by Ekta Walia. This book is one of the most popular and comprehensive textbooks on the subject, covering topics such as process management, memory management, file system management, device management, security and protection, types and examples of operating systems, and future trends and developments in operating systems. In this article, we will provide you with a comprehensive guide on what this book is about, why it is important, and how you can download it for free.
operating system concepts by ekta walia free
What is an operating system?
An operating system (OS) is a software program that manages the hardware and software resources of a computer system. It acts as an interface between the user and the computer, providing services such as executing applications, managing files and directories, controlling input and output devices, allocating memory and CPU time, handling errors and exceptions, enforcing security policies, and facilitating communication among processes. An operating system also provides a platform for developing and running other software programs.
What are the main concepts of operating systems?
Operating systems are complex and dynamic systems that involve many concepts and principles. Some of the main concepts of operating systems are:
Process: A process is a program in execution. It consists of a set of instructions, data, registers, stack, heap, and other resources. A process can be in one of several states: new, ready, running, waiting, or terminated. A process can also create other processes (called child processes) or communicate with other processes (using interprocess communication mechanisms).
Memory: Memory is the storage area where programs and data are loaded for execution. Memory can be divided into different segments or regions, such as code segment (where the instructions are stored), data segment (where the variables are stored), stack segment (where the function calls and local variables are stored), heap segment (where the dynamic memory allocation takes place), etc. Memory can also be organized into different levels or hierarchies, such as cache memory (which is faster but smaller than main memory), main memory (which is larger but slower than cache memory), secondary memory (which is even larger but slower than main memory), etc.
File: A file is a collection of related data that is stored on a secondary storage device (such as a disk or a tape). A file can have different attributes, such as name, type, size, location, permission, etc. A file can also have different operations, such as create, open, read, write, close, delete, rename, etc. A file can be organized into different structures or formats, such as sequential file (where the records are stored one after another), indexed file (where the records are stored in a sorted order and accessed by an index), direct file (where the records are stored in a fixed location and accessed by a hash function), etc.
Device: A device is a hardware component that can perform input or output operations. A device can have different characteristics, such as speed, capacity, reliability, etc. A device can also have different types, such as character device (which transfers data one character at a time), block device (which transfers data one block at a time), network device (which transfers data over a network), etc. A device can be managed by different methods, such as polling (where the CPU checks the status of the device periodically), interrupt (where the device notifies the CPU when it is ready for an operation), direct memory access (where the device transfers data directly to or from the memory without involving the CPU), etc.
Security and protection: Security and protection are the mechanisms that ensure the confidentiality, integrity, and availability of the system and its resources. Security involves preventing unauthorized access or misuse of the system and its resources, while protection involves enforcing policies and rules that govern the access and use of the system and its resources. Some of the security and protection techniques are encryption (which transforms data into an unreadable form), authentication (which verifies the identity of a user or a process), authorization (which determines what a user or a process can do), auditing (which records and monitors the activities of a user or a process), firewall (which filters and controls the network traffic), antivirus (which detects and removes malicious software), etc.
Who is Ekta Walia and why is her book important?
Ekta Walia is a professor of computer science and engineering at Guru Nanak Dev Engineering College in Ludhiana, India. She has more than 15 years of teaching and research experience in the field of operating systems, distributed systems, cloud computing, big data, artificial intelligence, and machine learning. She has published more than 50 papers in reputed journals and conferences, and has authored several books on operating systems, data structures, algorithms, programming languages, etc.
Her book Operating System Concepts is one of the most comprehensive and up-to-date textbooks on operating systems. It covers both the theoretical and practical aspects of operating systems, with examples from real-world systems such as Linux, Windows, Android, iOS, etc. It also includes numerous exercises, projects, case studies, review questions, and multiple-choice questions to help students test their understanding and apply their knowledge. The book is suitable for undergraduate and postgraduate students of computer science and engineering, as well as for professionals who want to learn or refresh their skills in operating systems.
The Structure and Functions of Operating Systems
In this section, we will discuss the structure and functions of operating systems in detail. We will explain how operating systems are organized into different components or modules, and how they perform different tasks or functions to manage the hardware and software resources of a computer system.
Process management
Process management is the function of operating systems that deals with creating, executing, suspending, resuming, terminating, scheduling, synchronizing, communicating, and coordinating processes. Process management involves the following sub-functions:
Process creation: This sub-function creates new processes by allocating memory space, loading program code and data, initializing registers and variables, setting process attributes (such as priority, state, identifier, etc.), creating process control block (PCB) (which contains all the information about a process), etc.
Process execution: This sub-function executes processes by switching between them using context switching (which saves the current state of a process and restores the state of another process) and dispatching (which assigns a processor to a ready process). Process execution also involves handling interrupts (which are signals from devices or software that indicate an event or an error) and exceptions (which are errors or faults that occur during program execution).
Process suspension: This sub-function suspends processes by moving them from the ready queue to the waiting queue when they are blocked by an event or a resource request. Process suspension also involves releasing some resources (such as CPU time) that are held by the suspended processes.
Process resumption: This sub-function resumes processes by moving them from the waiting queue to the ready queue when they are unblocked by an event or a resource release. Process resumption also involves acquiring some resources (such as CPU time) that are needed by the resumed processes.
Memory management
Memory management is the function of operating systems that deals with allocating, deallocating, protecting, sharing, and organizing memory space for processes, files, and devices. Memory management involves the following sub-functions:
Memory allocation: This sub-function allocates memory space to processes by using different techniques, such as static allocation (which assigns a fixed amount of memory to a process at compile time), dynamic allocation (which assigns a variable amount of memory to a process at run time), contiguous allocation (which assigns a contiguous block of memory to a process), non-contiguous allocation (which assigns multiple non-contiguous blocks of memory to a process), etc.
Memory deallocation: This sub-function deallocates memory space from processes by using different techniques, such as explicit deallocation (which frees the memory space when a process terminates or when it explicitly releases it), implicit deallocation (which frees the memory space when a process exits a scope or when it is garbage collected), etc.
Memory protection: This sub-function protects memory space from unauthorized or illegal access or modification by using different techniques, such as base and limit registers (which define the valid range of addresses for a process), segmentation (which divides the memory space into logical segments with different attributes and permissions), paging (which divides the memory space into fixed-size pages with different attributes and permissions), virtual memory (which maps the logical address space of a process to the physical address space of the memory), etc.
Memory sharing: This sub-function allows multiple processes to share some parts of the memory space by using different techniques, such as shared memory (which creates a common region of memory that can be accessed by multiple processes), message passing (which transfers data between processes using messages), memory mapping (which maps a file or a device to a region of memory that can be accessed by multiple processes), etc.
Memory organization: This sub-function organizes the memory space into different levels or hierarchies to optimize the performance and utilization of the memory by using different techniques, such as cache memory (which is a small and fast memory that stores frequently used data), main memory (which is a large and slow memory that stores all the data that are currently in use), secondary memory (which is an even larger and slower memory that stores all the data that are not currently in use), etc.
File system management
File system management is the function of operating systems that deals with creating, deleting, opening, closing, reading, writing, renaming, moving, copying, and organizing files and directories on secondary storage devices. File system management involves the following sub-functions:
File creation: This sub-function creates new files by allocating disk space, assigning file attributes (such as name, type, size, location, permission, etc.), creating file control block (FCB) (which contains all the information about a file), etc.
File deletion: This sub-function deletes files by deallocating disk space, removing file attributes, deleting file control block, etc.
File opening: This sub-function opens files by locating them on the disk, checking their permissions, creating file descriptor (which contains the current status of a file), etc.
File closing: This sub-function closes files by updating their attributes, releasing their resources, deleting file descriptor, etc.
File reading: This sub-function reads data from files by locating them on the disk, transferring them to the buffer, updating their status, etc.
File writing: This sub-function writes data to files by locating them on the disk, transferring them from the buffer, updating their status, etc.
File renaming: This sub-function renames files by changing their name attribute and updating their file control block.
File moving: This sub-function moves files from one location to another on the disk by changing their location attribute and updating their file control block.
File copying: This sub-function copies files from one location to another on the disk by creating a new file with the same data and attributes as the original file.
File organization: This sub-function organizes files into directories or folders that can have different attributes, such as name, type, size, location, permission, etc. A directory can also have different operations, such as create, delete, open, close, list, search, etc. A directory can also have different structures or formats, such as single-level directory (which has only one level of directories), two-level directory (which has two levels of directories), tree-structured directory (which has a hierarchical structure of directories), acyclic-graph directory (which allows multiple paths to a file), etc.
Device management
Device management is the function of operating systems that deals with controlling, allocating, deallocating, and accessing input and output devices. Device management involves the following sub-functions:
Device control: This sub-function controls devices by sending commands and receiving status information from them using device drivers (which are software programs that communicate with devices) and device controllers (which are hardware components that interface with devices).
Device allocation: This sub-function allocates devices to processes by using different techniques, such as dedicated allocation (which assigns a device to a process exclusively), shared allocation (which assigns a device to multiple processes concurrently), spooling (which assigns a device to a process temporarily by using a buffer), etc.
Device deallocation: This sub-function deallocates devices from processes by using different techniques, such as explicit deallocation (which frees the device when a process terminates or when it explicitly releases it), implicit deallocation (which frees the device when a process exits a scope or when it is preempted), etc.
Device access: This sub-function accesses devices by using different techniques, such as sequential access (which accesses data in a sequential order), direct access (which accesses data in a random order), indexed access (which accesses data using an index), etc.
Security and protection
Security and protection are the functions of operating systems that ensure the confidentiality, integrity, and availability of the system and its resources. Security and protection involve the following sub-functions:
Encryption: This sub-function transforms data into an unreadable form by using different techniques, such as symmetric encryption (which uses the same key for encryption and decryption), asymmetric encryption (which uses different keys for encryption and decryption), hash function (which generates a fixed-length value from a variable-length input), digital signature (which verifies the authenticity and integrity of a message), etc.
Authentication: This sub-function verifies the identity of a user or a process by using different techniques, such as password (which is a secret word or phrase that only the user knows), token (which is a physical object that only the user possesses), biometric (which is a physical or behavioral characteristic that only the user has), etc.
Authorization: This sub-function determines what a user or a process can do by using different techniques, such as access control list (ACL) (which is a list of permissions associated with each resource), role-based access control (RBAC) (which is a model that assigns roles to users and permissions to roles), mandatory access control (MAC) (which is a model that assigns security levels to users and resources and enforces rules based on them), discretionary access control (DAC) (which is a model that allows users to grant or revoke permissions to other users or resources), etc.
Auditing: This sub-function records and monitors the activities of a user or a process by using different techniques, such as log file (which is a file that stores the events or actions that occur in the system), audit trail (which is a sequence of records that shows the history of an event or action in the system), audit policy (which is a set of rules that defines what events or actions should be logged and how they should be handled), etc.
Firewall: This sub-function filters and controls the network traffic by using different techniques, such as packet filtering (which examines the header of each packet and allows or denies it based on predefined rules), stateful inspection (which examines the header and content of each packet and keeps track of the state of each connection), proxy server (which acts as an intermediary between the internal and external networks and performs various functions such as caching, filtering, logging, etc.), etc.
(which isolates a program in a virtual environment and monitors its actions), etc.
The Types and Examples of Operating Systems
In this section, we will discuss the types and examples of operating systems in detail. We will explain how operating systems are classified into different categories based on their design, functionality, and application. We will also provide some examples of operating systems that belong to each category.
Batch operating systems
Batch operating systems are operating systems that execute a batch or a group of similar jobs or tasks without any user interaction. Batch operating systems use a technique called batch processing, which involves loading a set of jobs or tasks into an input device (such as a card reader or a tape drive), executing them one by one in a sequential order, and producing the output in an output device (such as a printer or a tape drive). Batch operating systems are suitable for tasks that are repetitive, independent, and non-interactive, such as payroll processing, scientific computing, etc. Some examples of batch operating systems are IBM OS/360, MS-DOS, etc.
Multiprogramming operating systems
Multiprogramming operating systems are operating systems that execute multiple jobs or tasks concurrently by using a technique called multiprogramming, which involves loading multiple jobs or tasks into the main memory and switching between them using context switching. Multiprogramming operating systems use a technique called CPU scheduling, which determines which job or task should be executed next by the CPU based on some criteria or algorithm. Multiprogramming operating systems are suitable for tasks that are independent, interactive, and have varying CPU and I/O requirements, such as word processing, web browsing, etc. Some examples of multiprogramming operating systems are UNIX, Windows, Linux, etc.
Time-sharing operating systems
Time-sharing operating systems are operating systems that execute multiple jobs or tasks concurrently by using a technique called time-sharing, which involves dividing the CPU time into small intervals or slices and allocating them to different jobs or tasks in a round-robin fashion. Time-sharing operating systems use a technique called preemptive CPU scheduling, which allows the CPU to interrupt the execution of a job or