Introduction to Operating System Last Updated : 06 Aug, 2025 Comments Improve Suggest changes Like Article Like Report An operating system acts as an intermediary between the user of a computer and computer hardware. In short its an interface between computer hardware and user. The purpose of an operating system is to provide an environment in which a user can execute programs conveniently and efficiently. An operating system is software that manages computer hardware and software. The hardware must provide appropriate mechanisms to ensure the correct operation of the computer system and to prevent user programs from interfering with the proper operation of the system. The operating system (OS) is a program that runs at all times on a computer. All other programs, including application programs, run on top of the operating system.It does assignment of resources like memory, processors and input / output devices to different processes that need the resources. The assignment of resources has to be fair and secure. Operating System as a User Interface: User (Interacts with the system) System and application programs (Software tools for the user) Operating system (Manages hardware and software resources) Hardware (Physical computing devices)Every general-purpose computer consists of hardware, an operating system(s), system programs and application programs. The hardware consists of memory, CPU, ALU, I/O devices, peripheral devices and storage devices. The system program consists of compilers, loaders, editors, OS, etc. Conceptual View of Computer System Every computer must have an operating system to run other programs. The operating system coordinates the use of the hardware among the various system programs and application programs for various users. It simply provides an environment within which other programs can do useful work. An OS is a package of some programs that runs on a computer machine, allowing it to perform efficiently. It manages the simple tasks of recognizing input from the keyboard, managing files and directories on disk, displaying output on the screen and controlling peripheral devices. Goals of Operating System Primary GoalsThe primary goals of an operating system (OS) are to provide a easy to use and convenient environment for executing user programs. User Convenience : It should be easy to use, providing a user-friendly interface and making it simple to interact with the system.Program Execution: It facilitates the execution of user programs, providing the necessary environment and services for them to run.Resource Management: The OS manages and allocates the computer's resources, including the CPU, memory, disk storage, and input/output devices, to ensure fair utilization.Security: The OS protects the system and user data from unauthorized access, ensuring the confidentiality, integrity, and availability of information.Secondary GoalsEfficient Resource Utilization: It should aim to maximize the performance and utilization of computer resources like CPU, Memory and IO devices, ensuring that the system runs smoothly and efficiently. Reliability: It should be robust and reliable, able to handle errors and exceptions gracefully, ensuring that the system continues to operate smoothly. It should be modular in design and easy to debug.List of Common Operating Systems There are multiple types of operating systems each having its own unique features: Windows OS Developer : Microsoft Key Features : User-friendly interface, software compatibility, hardware support, Strong gaming support. Advantages : Easy to use for most users, Broad support from third-party applications ,Frequent updates and support. Typical Use Cases : Personal computing, Business environment, Gaming. macOS Developer : Apple. Key Features : Sleek, intuitive user interface, Strong integration with other Apple products, Robust security features, High performance and stability. Advantages : Optimized for Apple hardware, Seamless experience across Apple ecosystem, Superior graphics and multimedia capabilities. Typical Use Cases : Creative industries (design, video editing, music production), Personal computing, Professional environments. Linux Developer : Community-driven (various distributions). Key Features : Open-source and highly customizable, Robust security and stability, Lightweight and can run on older hardware, Large selection of distributions (e.g., Ubuntu, Fedora, Debian). Advantages : Free to use and distribute, Strong community support, Suitable for servers and development environments. Typical Use Cases : Servers and data centers, Development and programming, Personal computing for tech enthusiasts. Unix Developer: Originally AT&T Bell Labs, various commercial and open-source versions available Key Features: Multiuser and multitasking capabilities, Strong security and stability, Powerful command-line interface, Portability across different hardware platforms Advantages: Reliable and robust performance, Suitable for high-performance computing and servers, Extensive support for networking Typical Use Cases: Servers and workstations, Development environments, Research and academic settings History of Operating System The operating system has been evolving through the years. The following table shows the history of OS. EraKey DevelopmentsExamples1956The first Operating System was GM-NAA I/O in 1956 by General Motors. GM-NAA I/O (1956)1960sIBM developed a time sharing system TSS/360OS/360, DOS/360 and TSS/3601970sUnix popularized simplicity and multitasking; rise of personal computers with basic OSs.Unix (1971), CP/M (1974)1980sGUI-based OSs gained traction; networking features became standard.Apple Macintosh (1984), Windows (1985)1990sOpen-source Linux emerged; GUIs in Windows and Mac OS improved.Linux (1991), Windows 95 (1995)2000s-PresentMobile OSs dominated; cloud and virtualization technologies advanced computing.iOS (2007), Android (2008)Characteristics of Operating Systems Let us now discuss some of the important characteristic features of operating systems: Device Management: The operating system keeps track of all the devices. So, it is also called the Input/Output controller that decides which process gets the device, when and for how much time. File Management: It allocates and de-allocates the resources and also decides who gets the resource. Job Accounting: It keeps track of time and resources used by various jobs or users. Error-detecting Aids: These contain methods that include the production of dumps, traces, error messages and other debugging and error-detecting methods. Memory Management: It is responsible for managing the primary memory of a computer, including what part of it are in use by whom also check how much amount free or used and allocate process Processor Management: It allocates the processor to a process and then de-allocates the processor when it is no longer required or the job is done. Security: It prevents unauthorized access to programs and data using passwords or some kind of protection technique. Layered Design of Operating System Fig. Layered OS The extended machine provides operations like context save, dispatching, swapping and I/O initiation. The operating system layer is located on top of the extended machine layer. This arrangement considerably simplifies the coding and testing of OS modules by separating the algorithm of a function from the implementation of its primitive operations. It is now easier to test, debug and modify an OS module than in a monolithic OS. We say that the lower layer provides an abstraction that is the extended machine. We call the operating system layer the top layer of the OS. Components of an Operating Systems There are two basic components of an Operating System. Shell is the outermost layer of the Operating System and it handles the interaction with the user. It interprets input for the OS and handles the output from the OS. Kernel is the core component of operating system. The kernel is the primary interface between the Operating system and Hardware. Recommended Next Reads32 vs 64-bit Operating Systems Functions of OS for more detailsHistory of Operating Systems for more about history. Introduction to Operating System Visit Course Comment More infoAdvertise with us Next Article What is an Operating System? GeeksforGeeks Improve Article Tags : Misc Operating Systems GATE CS school-programming CBSE - Class 11 +1 More Practice Tags : Misc Similar Reads Operating System Tutorial An Operating System(OS) is a software that manages and handles hardware and software resources of a computing device. Responsible for managing and controlling all the activities and sharing of computer resources among different running applications.A low-level Software that includes all the basic fu 4 min read OS BasicsWhat is an Operating System?An Operating System is a System software that manages all the resources of the computing device. Acts as an interface between the software and different parts of the computer or the computer hardware. Manages the overall resources and operations of the computer. 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But threa 7 min read CPU SchedulingCPU Scheduling in Operating SystemsCPU scheduling is a process used by the operating system to decide which task or process gets to use the CPU at a particular time. This is important because a CPU can only handle one task at a time, but there are usually many tasks that need to be processed. The following are different purposes of a 8 min read Preemptive and Non-Preemptive SchedulingIn operating systems, scheduling is the method by which processes are given access the CPU. Efficient scheduling is essential for optimal system performance and user experience. There are two primary types of CPU scheduling: preemptive and non-preemptive. Understanding the differences between preemp 4 min read Multiple-Processor Scheduling in Operating SystemIn multiple-processor scheduling multiple CPUs are available and hence Load Sharing becomes possible. However multiple processor scheduling is more complex as compared to single processor scheduling. 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In other word 5 min read Memory & Disk ManagementMemory Management in Operating SystemMemory is a hardware component that stores data, instructions and information temporarily or permanently for processing. It consists of an array of bytes or words, each with a unique address. Memory holds both input data and program instructions needed for the CPU to execute tasks.Memory works close 7 min read Fixed (or static) Partitioning in Operating SystemFixed partitioning, also known as static partitioning, is one of the earliest memory management techniques used in operating systems. In this method, the main memory is divided into a fixed number of partitions at system startup, and each partition is allocated to a process. These partitions remain 8 min read Variable (or Dynamic) Partitioning in Operating SystemIn operating systems, Memory Management is the function responsible for allocating and managing a computer’s main memory. The memory Management function keeps track of the status of each memory location, either allocated or free to ensure effective and efficient use of Primary Memory. Below are Memo 4 min read Paging in Operating SystemPaging is the process of moving parts of a program, called pages, from secondary storage (like a hard drive) into the main memory (RAM). The main idea behind paging is to break a program into smaller fixed-size blocks called pages.To keep track of where each page is stored in memory, the operating s 8 min read Segmentation in Operating SystemA process is divided into Segments. The chunks that a program is divided into which are not necessarily all of the exact sizes are called segments. Segmentation gives the user's view of the process which paging does not provide. Here the user's view is mapped to physical memory. Types of Segmentatio 4 min read Segmentation in Operating SystemA process is divided into Segments. The chunks that a program is divided into which are not necessarily all of the exact sizes are called segments. Segmentation gives the user's view of the process which paging does not provide. Here the user's view is mapped to physical memory. Types of Segmentatio 4 min read Page Replacement Algorithms in Operating SystemsIn an operating system that uses paging for memory management, a page replacement algorithm is needed to decide which page needs to be replaced when a new page comes in. Page replacement becomes necessary when a page fault occurs and no free page frames are in memory. in this article, we will discus 7 min read File Systems in Operating SystemA computer file is defined as a medium used for saving and managing data in the computer system. The data stored in the computer system is completely in digital format, although there can be various types of files that help us to store the data.File systems are a crucial part of any operating system 8 min read File Systems in Operating SystemA computer file is defined as a medium used for saving and managing data in the computer system. The data stored in the computer system is completely in digital format, although there can be various types of files that help us to store the data.File systems are a crucial part of any operating system 8 min read Advanced OSMultithreading in Operating SystemA thread is a path that is followed during a program’s execution. The majority of programs written nowadays run as a single thread. For example, a program is not capable of reading keystrokes while making drawings. These tasks cannot be executed by the program at the same time. This problem can be s 7 min read Compaction in Operating SystemCompaction is a technique to collect all the free memory present in the form of fragments into one large chunk of free memory, which can be used to run other processes. It does that by moving all the processes towards one end of the memory and all the available free space towards the other end of th 3 min read Belady's Anomaly in Page Replacement AlgorithmsBelady's Anomaly is a phenomenon in operating systems where increasing the number of page frames in memory leads to an increase in the number of page faults for certain page replacement algorithms. Normally, as more page frames are available, the operating system has more flexibility to keep the nec 11 min read Techniques to handle ThrashingPrerequisite - Virtual Memory Thrashing is a condition or a situation when the system is spending a major portion of its time servicing the page faults, but the actual processing done is very negligible. Causes of thrashing:High degree of multiprogramming.Lack of frames.Page replacement policy.Thras 6 min read Free Space Management in Operating SystemFree space management is a critical aspect of operating systems as it involves managing the available storage space on the hard disk or other secondary storage devices. The operating system uses various techniques to manage free space and optimize the use of storage devices. Here are some of the com 7 min read RAID (Redundant Arrays of Independent Disks)RAID is a technique that combines multiple hard drives or SSDs into a single system to improve performance, data safety, or both. If one drive fails, data can still be recovered from the others.RAID helps store data more reliably and efficiently by spreading or copying data across drives. Different 13 min read PracticeLast Minute Notes – Operating SystemsAn Operating System (OS) is a system software that manages computer hardware, software resources, and provides common services for computer programs. It acts as an interface between the user and the computer hardware.Table of Content Types of Operating System (OS): ThreadsProcessCPU Scheduling Algor 15+ min read Operating System Interview QuestionsAn operating system acts as a GUI between the user and the computer system. In other words, an OS acts as an intermediary between the user and the computer hardware, managing resources such as memory, processing power, and input/output operations. Here some examples of popular operating systems incl 15+ min read Operating Systems - GATE CSE Previous Year QuestionsThe Operating System(OS) subject has high importance in GATE CSE exam because:large number of questions nearly 10-12% of the total asked significant weightage (9-11 marks) across multiple years which can also be seen in the below given table:YearApprox. Marks from OSNumber of QuestionsDifficulty Lev 2 min read Like