3.1 The operating system layer

Operating System 

An operating system (OS) is the software that manages computer hardware and software resources and provides common services for computer programs. The OS acts as an intermediary between users and the computer hardware. It performs various essential functions, including:

Functions of an Operating System:

  1. Process Management:
    • Manages the execution of processes, including multitasking, scheduling, and termination.
    • Ensures that each process gets enough CPU time to function properly.
  2. Memory Management:
    • Handles allocation and deallocation of memory spaces as needed by programs during their execution.
    • Manages both the physical memory (RAM) and virtual memory.
  3. File System Management:
    • Manages files on storage devices, providing a way to store, retrieve, and update data.
    • Organizes files and directories for efficient storage and retrieval.
  4. Device Management:
    • Controls and coordinates the use of hardware peripherals like printers, disk drives, and network interfaces.
    • Implements drivers and other necessary software to interface with hardware.
  5. Security and Access Control:
    • Protects data and resources from unauthorized access and ensures privacy.
    • Implements authentication mechanisms and access control policies.

 

Operating System Layer 

 

An operating system is typically structured in layers, each providing specific services and functionality. This layered approach helps in organizing the complexities of the system, making it easier to understand, manage, and develop. 

 

 

Hardware Layer

This is the lowest layer, directly interacting with the physical hardware components such as CPU, memory, storage devices, and peripheral devices like keyboards, mice, and printers.

Functions:

  • Provides the physical foundation for the system.
  • Executes machine-level instructions.
  • Communicates directly with the firmware and device drivers.

 

Kernel Layer

The kernel is the core component of the operating system. It provides essential services, such as process management, memory management, device management, and system calls. 

The kernel manages the communication between hardware and software components, ensuring that programs can run efficiently and access hardware resources securely.

Functions:

  • Core of the operating system.
  • Manages CPU operations, memory management, and device management.
  • Handles process scheduling, context switching, and interrupts.
  • Provides system calls for user applications to interact with hardware.

 

Shell 

 

The shell layer of an operating system serves as the intermediary between the user and the system's kernel. It interprets and executes commands entered by the user, providing a user-friendly way to interact with the operating system. Shells can be either command-line interfaces (CLI) or graphical user interfaces (GUI).


 

Application Layer

These are the programs that users interact with directly to perform various tasks like word processing, web browsing, email, gaming, etc. Applications rely on the services provided by the lower layers of the operating system to access hardware resources and perform their functions.

Functions:

  • Directly used by end-users to perform various tasks.
  • Interacts with user space and system libraries to achieve desired functionalities.