An operating system (OS) is the software that acts as an interface between a computer's hardware and the user, managing processes, memory, files, and devices so applications can run without directly controlling the hardware. This operating system tutorial covers everything from operating system basics, processes, threads, and memory management, through advanced topics like CPU scheduling, deadlocks, and synchronization. Every device you use runs an OS: Windows, macOS, and Linux dominate desktops, while Android and iOS together account for the vast majority of mobile devices worldwide. Understanding OS fundamentals matters well beyond exams; process scheduling, memory management, and deadlock handling are among the most frequently tested topics in technical interviews at top product companies, because they reveal how well you understand what's actually happening beneath the code you write. This tutorial builds these operating system basics step by step, from what an OS does at the most fundamental level through process synchronization, disk management, and real interview-style problems, giving you both conceptual clarity and practical, interview-ready depth.
What is an Operating System(OS)?
In the Computer System (comprises Hardware and software), Hardware can only understand machine code (in the form of 0 and 1) which doesn't make any sense to a naive user.
We need a system that can act as an intermediary and manage all the processes and resources present in the system.
An Operating System can be defined as an interface between the user and hardware. It's responsible for executing all processes, resource allocation, CPU management, file management, and a range of other tasks, exactly what this operating system tutorial builds up from the ground.
Basic Concepts of Operating Systems
Before going module by module, it helps to see how the basic concepts of operating system design fit together, most of what follows in this tutorial builds on these ideas:
- Process: A program in execution, the OS tracks each process's state, memory, and resources through a Process Control Block (PCB).
- Thread: A lightweight unit of execution within a process, allowing multiple tasks to run concurrently within the same program.
- Memory Management: How the OS allocates, tracks, and reclaims memory for running processes, including virtual memory techniques that let programs use more memory than is physically available.
- CPU Scheduling: The set of algorithms the OS uses to decide which process gets CPU time next, balancing fairness, throughput, and responsiveness.
- Synchronization: Mechanisms (like mutexes and semaphores) that prevent multiple processes or threads from corrupting shared data when accessing it at the same time.
- Deadlock: A situation where two or more processes are stuck waiting on each other indefinitely, a classic OS problem with well-known prevention and avoidance strategies.
Each of these is covered in dedicated modules above, but understanding how they connect is what makes the rest of this operating system tutorial click.
Process vs Thread: What's the Difference?
This is one of the most commonly confused pairs in operating system basics, and one of the most frequently asked interview questions:
| Process | Thread | |
|---|---|---|
| Definition | An independent program in execution | A lightweight unit of execution within a process |
| Memory | Has its own separate memory space | Shares memory space with other threads in the same process |
| Creation overhead | Higher, more resources to allocate | Lower, faster to create and switch between |
| Communication | Requires inter-process communication (IPC) | Can communicate directly through shared memory |
Understanding this distinction is foundational before moving into scheduling and synchronization, both covered in depth in the modules above.
History of Operating System
The operating system is a system program that serves as an interface between the computing system and the end-user. Operating systems create an environment where the user can run any programs or communicate with software or applications in a comfortable and well-organized way.
Furthermore, an operating system is a software program that manages and controls the execution of application programs, software resources and computer hardware.
It also helps manage the software/hardware resources, such as file management, memory management, input/ output and many peripheral devices like a disk drive, printers, etc.
Examples of Operating System
- Laptops, tablets, and desktop computers all run operating systems that you've probably heard of. Some examples include versions of Microsoft Windows (like Windows 11, Windows 10, Windows 8, Windows 7), Apple's macOS (formerly OS X), Chrome OS, and various Unix and Linux distribution lists.
- Your smartphone runs mobile operating systems, probably either Apple's iOS or Google's Android.
- Servers, like those that host the websites you visit or serve the videos you watch, typically run specialized operating systems. Some examples include Windows Server, Linux, and FreeBSD.
Functions of Operating system
Important functions of an operating Systems:
- Security – The operating system uses password protection to protect user data and similar other techniques. it also prevents unauthorized access to programs and user data.
- Control over system performance – Monitors overall system health to help improve performance. records the response time between service requests and system response to have a complete view of the system health.
- Job accounting – Operating system Keeps track of time and resources used by various tasks and users, this information can be used to track resource usage for a particular user or group of users.
Features of Operating System
Here are some common features of modern operating systems:
- Process Management: The OS manages the execution of multiple processes and threads on the system, including scheduling, synchronization, and communication between processes.
- Memory Management: The OS manages the allocation and deallocation of memory resources to running processes and manages virtual memory to enable efficient use of physical memory.
- Device Management: The OS manages the input and output devices of the computer system, including the keyboard, mouse, storage devices, and network devices.
- File System Management: The OS manages the organization, storage, and retrieval of files and directories on the storage devices.
- Security Management: The OS provides security features to protect the system from unauthorized access, including authentication, authorization, and encryption.
Components of Operating System
The main components of an operating system are:
- Kernel: The kernel is the core component of the operating system that manages system resources, including CPU, memory, and input/output (I/O) devices. It provides low-level services to other components of the operating system and manages system calls and interrupts.
- Device Drivers: Device drivers are software components that enable the operating system to communicate with hardware devices, such as printers, scanners, and network adapters. They provide a standard interface between the hardware and the operating system and handle device-specific commands and data.
- File System: The file system is a component of the operating system that manages files and directories on the storage devices. It provides a hierarchical structure for organizing files and directories and manages file access permissions and security.
- User Interface: The user interface is the component of the operating system that enables users to interact with the computer system. It provides a graphical user interface (GUI), command-line interface (CLI), and other user-friendly interfaces for users to interact with the system.
- System Libraries: System libraries are collections of software components that provide common functions and routines for applications to use. They include standard libraries for programming languages, such as C and Java, and system-specific libraries for accessing operating system features.
Types of Operating Systems
There are several types of operating systems, each with its own characteristics and purposes:
- Single-user, Single-task: This type of operating system is designed to run on a single computer and can only perform one task at a time. Examples include MS-DOS and early versions of Apple Macintosh.
- Single-user, Multi-tasking: This type of operating system allows multiple applications to run at the same time on a single computer. Examples include Microsoft Windows, macOS, and Linux.
- Multi-user: Multi-user operating systems allow multiple users to access the same computer simultaneously. Each user has their own account and can run their own applications. Examples include Unix, Linux, and Windows Server.
- Real-time: Real-time operating systems are designed for applications that require immediate response times, such as industrial control systems and medical equipment. Examples include VxWorks and QNX.
- Network: Network operating systems are designed to manage and control network resources, such as servers, printers, and network storage devices. Examples include Novell NetWare and Windows Server.
- Mobile: Mobile operating systems are designed for use on mobile devices, such as smartphones and tablets. Examples include Android, iOS, and Windows Phone.
- Embedded: Embedded operating systems are designed for use in embedded systems, such as automotive systems, consumer electronics, and industrial control systems. Examples include Linux and VxWorks.
Operating Systems Market Share
The following points show the market share from March 2022 to March 2023:
- Windows is the most popular desktop/laptop operating system, with a global market share of 74.15%.
- macOS is the second most popular desktop/laptop operating system, with a global market share of 16.78%.
- Linux is a distant third in the desktop/laptop market, with a global market share of 1.98%.
- Android is the most popular mobile operating system, with a global market share of 72.92%.
- iOS is the second most popular mobile operating system, with a global market share of 26.44%.
- KaiOS, a mobile operating system designed for feature phones, has a global market share of 0.48%.
The market share for operating systems can vary significantly by region and industry.The market share figures are subject to change over time, as new operating systems are released and user preferences evolve.
Operating Systems Market Share in 2026
Based on StatCounter usage data through mid-2026:
- Desktop: Windows remains dominant at roughly 62-67% of measured traffic, followed by macOS at around 12-15% and Linux at 3-4%. A significant and growing "Unknown" share (15-20%) has emerged since Windows 10 reached end of support in October 2025, as more users adopt privacy settings that mask their OS from tracking, so Windows' real share is likely understated by these figures.
- Mobile: Android holds roughly 69-70% of the global mobile market, with iOS at around 29-30%. Together, they account for over 99% of mobile devices worldwide, every other mobile OS (Tizen, KaiOS) is now statistically negligible.
Exact figures vary meaningfully by tracking source and methodology, so treat these as directional rather than precise, StatCounter is the most commonly cited reference point, but IDC and Counterpoint Research report somewhat different numbers due to differences in what they measure (web traffic vs. shipments vs. active devices).
Error detecting aids
The operating system constantly monitors the system to detect errors and avoid the malfunctioning of a computer system.
Memory Management
The operating system manages the Primary Memory or Main Memory. Main memory is made up of a large array of bytes or words where each byte or word is assigned a certain address. Main memory is fast storage and it can be accessed directly by the CPU.
Processor Management – In a multiprogramming environment, the OS decides the order in which processes have access to the processor, and how much processing time each process has.
Processor Management
In a multiprogramming environment, the OS decides the order in which processes get access to the processor, and how much processing time each one receives.
Device Management
An OS manages device communication via their respective drivers. It performs the following activities for device management. Keeps track of all devices connected to the system.
File Management
A file system is organized into directories for efficient or easy navigation and usage. These directories may contain other directories and other types of files. Features of Operating System
Protected and supervisor mode
Key functions handled in protected/supervisor mode:
- Allows disk access and file systems Device drivers Networking Security.
- Program Execution.
- Memory management Virtual Memory Multitasking.
- Handling I/O operations.
- Manipulation of the file system.
- Error Detection and handling.
- Resource allocation.
Why OS Concepts Still Matter for Technical Interviews
It's fair to wonder whether deep OS knowledge still matters when most day-to-day development happens several abstraction layers above the kernel. It does, process scheduling, memory management, deadlocks, and synchronization remain some of the most consistently asked topics in technical interviews at product companies, precisely because they test whether you understand what's actually happening underneath your code, not just whether you can write it.
This matters even more as systems grow more concurrent and distributed: understanding how the OS handles synchronization and deadlocks directly transfers to reasoning about race conditions and locking in the multi-threaded, multi-service systems most backend engineers work on today. A solid grip on operating system basics isn't just exam material, it's a genuine, transferable engineering skill.
Advantages of Operating System
- User Friendly. The interface provided by the GUI is much more user friendly compared to a command-line interface
- Security. It is a responsibility of an operating system to make sure each data present inside them is secure
- Sharing Resources: Enables multiple programs and users to share hardware resources efficiently.
- Hardware Accessibility**:** Provides a consistent way for software to access underlying hardware.
- Multitasking**:** Allows multiple programs to run concurrently.
Disadvantages of Operating System
- Cost: Unless it is an open-source operating system, generally all other platforms are considered to be expensive.
- Reliability: An operating system is a vital software for any computer
- Complexity**:** Modern OS internals are genuinely complex to fully master.
- Fragmentation: Inefficient memory or disk allocation over time can lead to fragmentation.
- Virus Attacks**:** As the layer everything else runs on, the OS is a high-value target for malware and exploits.
How Long Does It Take to Learn OS?
Most learners can grasp the basic concepts of operating system, processes, threads, and memory basics, in 2 to 4 weeks of consistent study. Reaching a comfortable, interview-ready level, including scheduling algorithms, deadlocks, and synchronization, typically takes 2 to 3 months. If your goal is specifically to learn OS for technical interviews, prioritize process scheduling, deadlock handling, and memory management, these come up most often.
Career Opportunity of Learning Operating System
A few roles where strong OS fundamentals matter directly:
- Operating Systems Specialist
- Operating Systems Programmer
- IT Administrator
- Systems / Backend Engineer - where OS-level concepts like concurrency and memory management inform day-to-day design decisions
- DevOps / Site Reliability Engineer - where understanding process and resource management directly affects debugging production issues
FAQs
What are the basic concepts of operating system I should learn first?
The basic concepts of operating system include processes, threads, memory management, CPU scheduling, and synchronization, all covered early in this tutorial before moving into deadlocks and file systems.
Is this a good operating system tutorial for beginners?
Yes, this operating system tutorial for beginners starts from core definitions and builds up to advanced topics like deadlocks and synchronization, assuming only basic computer familiarity.
How long does it take to learn OS?
Most learners grasp the fundamentals in 2-4 weeks and reach an interview-ready level in 2-3 months, especially when focusing on scheduling, deadlocks, and memory management first.
Why do technical interviews still test operating system basics?
Because they reveal whether a candidate understands what's happening beneath their code, concepts like scheduling and synchronization transfer directly to reasoning about concurrency in real backend systems.
What's the difference between a process and a thread?
A process is an independent program with its own memory space; a thread is a lightweight unit of execution that shares memory with other threads in the same process. See the comparison table above for more detail.
Where should I start if I just want to learn OS for interviews?
Start with processes, threads, and memory management, then move to CPU scheduling and deadlocks, these are the operating system basics most frequently tested in technical interviews.
Start Learning OS with Scaler
Once you've worked through this operating system tutorial, the natural next step is applying these concepts to systems design and technical interview preparation. Scaler's Modern Software and AI Engineering program builds on exactly this foundation with mentor-led, project-based learning.
Operating System Tutorial
The Operating System(OS) Tutorial is divided into various parts based on its functions such as Process Management, Process Synchronization, Deadlocks and File Management.
What is an Operating System(OS)?
In the Computer System (comprises Hardware and software), Hardware can only understand machine code (in the form of 0 and 1) which doesn't make any sense to a naive user.
We need a system that can act as an intermediary and manage all the processes and resources present in the system.
An Operating System can be defined as an interface between user and hardware. It is responsible for the execution of all the processes, Resource Allocation, CPU management, File Management and many other tasks.
History of Operating System
The operating system is a system program that serves as an interface between the computing system and the end-user. Operating systems create an environment where the user can run any programs or communicate with software or applications in a comfortable and well-organized way.
Furthermore, an operating system is a software program that manages and controls the execution of application programs, software resources and computer hardware.
It also helps manage the software/hardware resources, such as file management, memory management, input/ output and many peripheral devices like a disk drive, printers, etc.
Examples of Operating System
- Laptops, tablets, and desktop computers all run operating systems that you've probably heard of. Some examples include versions of Microsoft Windows (like Windows 11, Windows 10, Windows 8, Windows 7), Apple's macOS (formerly OS X), Chrome OS, and various Unix and Linux distribution lists.
- Your smartphone runs mobile operating systems, probably either Apple's iOS or Google's Android.
- Servers, like those that host the websites you visit or serve the videos you watch, typically run specialized operating systems. Some examples include Windows Server, Linux, and FreeBSD.
Functions of Operating system
Important functions of an operating Systems:
-
Security – The operating system uses password protection to protect user data and similar other techniques. it also prevents unauthorized access to programs and user data.
-
Control over system performance – Monitors overall system health to help improve performance. records the response time between service requests and system response to have a complete view of the system health.
-
Job accounting – Operating system Keeps track of time and resources used by various tasks and users, this information can be used to track resource usage for a particular user or group of users.
Features of Operating System
Here are some common features of modern operating systems:
-
Process Management: The OS manages the execution of multiple processes and threads on the system, including scheduling, synchronization, and communication between processes.
-
Memory Management: The OS manages the allocation and deallocation of memory resources to running processes and manages virtual memory to enable efficient use of physical memory.
-
Device Management: The OS manages the input and output devices of the computer system, including the keyboard, mouse, storage devices, and network devices.
-
File System Management: The OS manages the organization, storage, and retrieval of files and directories on the storage devices.
-
Security Management: The OS provides security features to protect the system from unauthorized access, including authentication, authorization, and encryption.
Components of Operating System
The main components of an operating system are:
-
Kernel: The kernel is the core component of the operating system that manages system resources, including CPU, memory, and input/output (I/O) devices. It provides low-level services to other components of the operating system and manages system calls and interrupts.
-
Device Drivers: Device drivers are software components that enable the operating system to communicate with hardware devices, such as printers, scanners, and network adapters. They provide a standard interface between the hardware and the operating system and handle device-specific commands and data.
-
File System: The file system is a component of the operating system that manages files and directories on the storage devices. It provides a hierarchical structure for organizing files and directories and manages file access permissions and security.
-
User Interface: The user interface is the component of the operating system that enables users to interact with the computer system. It provides a graphical user interface (GUI), command-line interface (CLI), and other user-friendly interfaces for users to interact with the system.
-
System Libraries: System libraries are collections of software components that provide common functions and routines for applications to use. They include standard libraries for programming languages, such as C and Java, and system-specific libraries for accessing operating system features.
Types of Operating Systems
There are several types of operating systems, each with its own characteristics and purposes:
-
Single-user, Single-task: This type of operating system is designed to run on a single computer and can only perform one task at a time. Examples include MS-DOS and early versions of Apple Macintosh.
-
Single-user, Multi-tasking: This type of operating system allows multiple applications to run at the same time on a single computer. Examples include Microsoft Windows, macOS, and Linux.
-
Multi-user: Multi-user operating systems allow multiple users to access the same computer simultaneously. Each user has their own account and can run their own applications. Examples include Unix, Linux, and Windows Server.
-
Real-time: Real-time operating systems are designed for applications that require immediate response times, such as industrial control systems and medical equipment. Examples include VxWorks and QNX.
-
Network: Network operating systems are designed to manage and control network resources, such as servers, printers, and network storage devices. Examples include Novell NetWare and Windows Server.
-
Mobile: Mobile operating systems are designed for use on mobile devices, such as smartphones and tablets. Examples include Android, iOS, and Windows Phone.
-
Embedded: Embedded operating systems are designed for use in embedded systems, such as automotive systems, consumer electronics, and industrial control systems. Examples include Linux and VxWorks.
Operating Systems Market Share
The following points show the market share from March 2022 to March 2023:
- Windows is the most popular desktop/laptop operating system, with a global market share of 74.15%.
- macOS is the second most popular desktop/laptop operating system, with a global market share of 16.78%.
- Linux is a distant third in the desktop/laptop market, with a global market share of 1.98%.
- Android is the most popular mobile operating system, with a global market share of 72.92%.
- iOS is the second most popular mobile operating system, with a global market share of 26.44%.
- KaiOS, a mobile operating system designed for feature phones, has a global market share of 0.48%.
The market share for operating systems can vary significantly by region and industry.The market share figures are subject to change over time, as new operating systems are released and user preferences evolve.
Error detecting aids
The operating system constantly monitors the system to detect errors and avoid the malfunctioning of a computer system.
Memory Management
The operating system manages the Primary Memory or Main Memory. Main memory is made up of a large array of bytes or words where each byte or word is assigned a certain address. Main memory is fast storage and it can be accessed directly by the CPU.
Processor Management – In a multiprogramming environment, the OS decides the order in which processes have access to the processor, and how much processing time each process has.
Device Management
An OS manages device communication via their respective drivers. It performs the following activities for device management. Keeps track of all devices connected to the system.
File Management
A file system is organized into directories for efficient or easy navigation and usage. These directories may contain other directories and other types of files. Features of Operating System
Protected and supervisor mode
- Allows disk access and file systems Device drivers Networking Security.
- Program Execution.
- Memory management Virtual Memory Multitasking.
- Handling I/O operations.
- Manipulation of the file system.
- Error Detection and handling.
- Resource allocation.
Advantages of Operating System
- User Friendly. The interface provided by the GUI is much more user friendly compared to a command-line interface
- Security. It is a responsibility of an operating system to make sure each data present inside them is secure
- Sharing Resources
- Hardware Accessibility
- Multitasking
Disadvantages of Operating System
- Cost - Unless it is an open-source operating system, generally all other platforms are considered to be expensive.
- Reliability - An operating system is a vital software for any computer
- Complexity
- Fragmentation
- Virus Attacks
Career Opportunity of Learning Operating System
- Operating Systems Specialist
- Operating Systems Programmer
- IT Administrator
