Computer Science

Architecture of Operating System (OS)

Published: 6th September, 2023

Anupama Raj

Content Writer at almaBetter

Discover the inner workings of computer systems as we delve deep into the architecture of operating systems. Explore the layered structures, types, and more.

The world of technology is propelled by complex systems that seamlessly manage our daily interactions with computers, smartphones, and more. At the heart of these systems lies the Operating System (OS), a crucial component often taken for granted. Understanding the architecture of an OS is like peering behind the curtain of a magic show, revealing the intricate machinery that makes everything work seamlessly.

In some operating systems, the read-only memory (ROM) contains firmware or boot code that initiates the system's startup process, adding an extra layer of complexity to the OS architecture. CPU scheduling, a key aspect of operating system architecture, ensures efficient task execution by determining the order and duration of processes' access to the CPU. In this extensive exploration, we will delve deep into the architecture of operating systems, from the foundational basics of OS and computer architecture to the specific architectures of well-known operating systems like Unix, Linux, and Android. We will also touch upon essential aspects like layered architecture, distributed OS, disk and file system architecture, and the different types of OS architectures.

Basics of OS and Computer Architecture

Before diving into the nitty-gritty details of the architecture of operating system, it's essential to grasp the fundamentals of both operating systems and computer architecture. An OS is a software that acts as an intermediary between a computer's hardware and its user applications. It manages resources, schedules tasks, and provides essential services, such as file management and device access.

Understanding the relationship between process and program is fundamental to comprehending how the architecture of an operating system manages the execution of software instructions and tasks.The basics of OS and computer architecture lay the groundwork for comprehending the intricate architecture of operating systems, serving as the foundation upon which the entire computing ecosystem is built. Understanding the architecture of OS begins with understanding the architecture of the computer system itself.

The Essence of Computer System Architecture in OS

At the heart of every computer lies a meticulously designed system architecture, a blueprint that governs the hardware components and their interactions. To appreciate the architecture of an operating system, one must fathom the inner workings of this computer system architecture. Key components include:

Central Processing Unit (CPU): The CPU is the brain of the computer, responsible for executing instructions and performing calculations. The OS interacts closely with the CPU, managing its usage to ensure efficient task execution.

Memory (RAM): Memory is where data and instructions are temporarily stored for fast access by the CPU. The OS manages memory allocation, ensuring that each process gets its fair share while preventing conflicts.

Input/Output Devices: Peripherals like keyboards, mice, displays, and printers connect to the computer via input/output ports. The OS facilitates communication between these devices and user applications.

Storage Devices: Hard drives, solid-state drives (SSDs), and other storage media store long-term data. The OS oversees storage management, ensuring data integrity and access.

Understanding how these hardware components interact and how the OS manages them is essential for comprehending OS architecture's intricacies.

Computer System Architecture in OS

The architecture of a computer system encompasses the design and organization of its hardware components. A typical computer system consists of a Central Processing Unit (CPU), memory, input/output devices, and storage devices. The OS interacts closely with these components to ensure efficient resource utilization.

Types of Architecture of Operating Systems

There are several approaches to designing an operating system, each with its unique architecture. The most common types of OS architecture include:

Monolithic Kernel Architecture: In this architecture, all OS services run in kernel mode, sharing the same address space. Examples of monolithic kernel-based OS include older versions of Unix and Linux.

Microkernel Architecture: Microkernels keep the kernel minimal, with most OS services running in user mode. This design aims to improve modularity and system stability. QNX and MINIX are examples of microkernel-based OS.

Hybrid Kernel Architecture: Combining elements of both monolithic and microkernel designs, hybrid kernels offer a balance between performance and modularity. Windows NT and macOS use a hybrid kernel architecture.

Now that we have laid the groundwork, let us explore the specific architectures of some well-known operating systems.

Architecture of Unix Operating System

The Unix operating system, known for its robustness and versatility, has a distinctive architecture that has influenced many other OS designs. The architecture of Unix OS is characterized by its simplicity and the philosophy of "everything is a file." Exploring the Unix OS architecture reveals a timeless and influential design that has left a lasting impact on the evolution of operating systems. Here's a glimpse into its core components:

Layered Architecture of Unix OS

Unix follows a layered architecture, where each layer provides a specific set of services and abstractions. These layers include:

Hardware Layer: This layer represents the actual computer hardware, including the CPU, memory, and storage devices.

Kernel Layer: The kernel is the core of the Unix OS, responsible for managing hardware resources, process scheduling, and file system operations. It is the bridge between user-level applications and the hardware.

Shell Layer: The shell is the user interface to the Unix OS. It interprets user commands and communicates with the kernel to execute them.

Utility Layer: Utilities are user-level programs that perform various tasks, from text processing to system maintenance. Unix provides a rich set of utilities that can be combined to perform complex operations.

Application Layer: This layer houses user applications, such as word processors, web browsers, and games. These applications interact with the Unix OS through system calls provided by the kernel.

The layered architecture of Unix OS promotes modularity and allows for easy extension and customization of the system. The layered architecture of OS, with its clear separation of functions and well-defined interfaces between layers, fosters a robust and adaptable system design.

Architecture of Linux Operating System

Linux, a Unix-like operating system, shares many architectural principles with Unix but also incorporates its unique features. Let's explore the architecture of Linux OS architecture in more detail:

Layered Architecture of Linux OS

The layered architecture of operating systems, characterized by its modular and hierarchical structure, plays a crucial role in simplifying system design and enhancing maintainability. Similar to Unix, Linux follows a layered architecture, with the following key layers:

Hardware Layer: This layer represents the physical computer hardware, including the CPU, RAM, storage devices, and input/output peripherals.

Kernel Layer: The Linux kernel serves as the core of the operating system, responsible for managing hardware resources, process management, and file system operations. It provides system calls that enable user-level programs to interact with the hardware.

Shell Layer: Linux offers various shells, such as Bash and Zsh, which act as command interpreters and provide a command-line interface for users to interact with the OS.

GNU Utilities Layer: Linux systems often include a set of GNU utilities, such as coreutils and textutils, which provide essential command-line tools for file manipulation, text processing, and system administration.

Desktop Environment Layer: In desktop Linux distributions, a graphical desktop environment like GNOME or KDE provides a user-friendly graphical interface, allowing users to interact with the system through windows, icons, and menus.

Application Layer: Linux supports a vast ecosystem of user applications, ranging from web browsers and office suites to multimedia players and development tools.

Linux's architecture emphasizes compatibility with Unix, making it a powerful and flexible operating system for a wide range of applications and environments. For those looking to delve deeper into the architecture of Linux operating systems, exploring Linux questions can be a valuable way to gain insights and expertise.

Architecture of Android Operating System

Android, the world's most widely used mobile operating system, has its architecture tailored to the specific requirements of mobile devices like smartphones and tablets. The architecture of Android OS is intricately crafted to meet the unique demands of mobile devices, providing a solid foundation for a vast ecosystem of applications. Understanding the Android OS architecture is crucial for developers and users alike.

Android OS Architecture

Android's architecture is based on a layered model, consisting of the following key layers:

Linux Kernel: At the core of Android lies the Linux kernel, which provides essential hardware abstraction, memory management, and process management capabilities. It serves as the foundation for the entire Android OS.

Libraries Layer: Above the kernel, Android includes a set of C/C++ libraries, including the Bionic libc library and libraries for graphics rendering, multimedia processing, and more. These libraries enable the development of native Android applications.

Android Runtime (ART): Android applications are primarily developed using Java or Kotlin. The Android Runtime (ART) compiles and executes Java bytecode, making it possible to run Android apps efficiently.

Application Framework: The Application Framework layer provides a set of high-level APIs and services that simplify app development. It includes components for user interface design, data storage, and communication between apps and system services.

Applications Layer: The top layer of Android OS comprises the user-facing applications. This includes system apps like the phone dialer, contacts, and settings, as well as third-party apps installed by users.

Android's architecture is designed with a focus on modularity, allowing device manufacturers and app developers to customize and extend the OS to suit their needs.

Read our latest blogs "List of Operating Systems" and "Booting in Operating System".

Architecture of Distributed Operating System

In the era of interconnected systems and cloud computing, distributed operating systems have become increasingly important. These OS architectures are designed to manage resources across multiple networked computers. Let's delve into the core components of a distributed operating system:

Distributed Operating System Architecture

A distributed operating system typically consists of the following components:

Network Communication Layer: Communication is the backbone of distributed systems. This layer handles network protocols, data transfer, and remote procedure calls (RPCs) to facilitate communication between distributed nodes.

Resource Management: In a distributed environment, resources can be distributed across multiple nodes. The resource management component allocates and manages resources such as CPU, memory, and storage, ensuring efficient utilization.

Distributed File System: Distributed operating systems often include a distributed file system that provides a unified view of files and data distributed across the network. Examples include Google's GFS (Google File System) and HDFS (Hadoop Distributed File System).

Process Synchronization: Coordinating processes and ensuring data consistency in a distributed environment is challenging. Distributed OS provides mechanisms for process synchronization, mutual exclusion, and distributed transactions.

Security and Authentication: Security is a critical concern in distributed systems. Distributed OS architectures implement robust authentication and authorization mechanisms to protect data and resources.

Fault Tolerance: Distributed systems must be resilient to failures, whether they are hardware failures or network issues. Fault tolerance mechanisms, such as redundancy and replication, are essential components of distributed OS architectures.

Distributed operating systems play a vital role in cloud computing, data centers, and large-scale networked applications, where the ability to scale and distribute resources is paramount.

Disk and File System Architecture in OS

Disk and file system architecture is a fundamental aspect of operating systems, as it governs how data is stored, retrieved, and organized on storage devices. Let's delve into the key components of disk and file system architecture:

Disk Architecture in OS

Disk architecture involves the organization of storage devices, such as hard drives and solid-state drives (SSDs). The primary components of disk architecture include:

Platters and Read/Write Heads: Traditional hard drives consist of rotating platters and read/write heads that move across the platters' surfaces to read and write data.

Sectors and Blocks: Data on storage devices is organized into sectors and blocks, with each block containing a fixed amount of data. The OS manages data at the block level.

File Allocation Table (FAT) or Inode Table: The OS maintains a table that maps file names to the physical locations of data blocks on the storage device. FAT is used in file systems like FAT16 and FAT32, while Unix-like systems use inode tables.

Caching and Buffering: To improve performance, OSes employ caching and buffering mechanisms to store frequently accessed data in RAM. This reduces the need to access data from the slower storage device.

File System Architecture in OS

File system architecture governs how files and directories are organized and accessed on storage devices. Common file system architectures include:

Hierarchical Structure: Most file systems, including Windows NTFS and Unix-like file systems, organize files and directories in a hierarchical tree-like structure, with a root directory at the top.

Metadata: File systems store metadata about files and directories, including file names, sizes, timestamps, and permissions. This metadata is crucial for file management and access control.

File Access Methods: File systems define methods for reading and writing data to files. These methods include sequential access, random access, and direct access.

Access Control Lists (ACLs) and Permissions: File systems implement access control mechanisms to restrict or grant access to files and directories based on user permissions and ACLs.

Journaling: Some modern file systems, like NTFS and ext4, incorporate journaling to enhance data integrity and recovery in the event of a system crash or power failure.

Understanding disk and file system architecture is essential for optimizing data storage and retrieval in operating systems.

Check out our latest article "Disk Scheduling Algorithms"


In this comprehensive exploration of the architecture of operating systems, we've journeyed from the basics of OS and computer architecture to the intricacies of specific OS designs, including Unix, Linux, and Android. We've also touched upon essential concepts like layered architecture, distributed operating systems, disk and file system architecture, and various types of OS architectures. Understanding the various types of architecture of operating systems allows us to appreciate the versatility and adaptability of these crucial software systems in different computing environments.

Operating systems serve as the invisible hand that orchestrates the harmony of computer systems, enabling us to perform tasks effortlessly. As technology continues to advance, so too will the architecture of operating systems, evolving to meet the demands of an ever-changing digital landscape. Understanding these architectural principles empowers us to harness the full potential of the digital world that surrounds us.

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