Core Functions and Composition Structure of Operating Systems

Process Management

Operating system's core function is Process Management, which is responsible for creating, scheduling, destroying processes and coordinating resource allocation.

• Process States: Processes typically exist in Ready, Running, Blocked, or Terminated states, and the operating system implements task scheduling through state transitions.
• Scheduling Algorithms: Common scheduling strategies include First-Come-First-Served (FCFS), Round-Robin (RR), and Priority Scheduling, aiming to balance system efficiency and fairness.
• Synchronization Mechanisms: Mechanisms like Semaphores and Mutexes resolve competition and collaboration between multiple processes, preventing Deadlock.

Memory Management

Memory Management is a key function of the operating system that ensures efficient program execution, primarily involving Physical Memory and Virtual Memory allocation and deallocation.

• Virtual Memory: Through Page or Segment techniques, programs map logical addresses to physical addresses, enabling memory protection and sharing.
• Page Replacement: When physical memory is insufficient, the operating system evicts Unnecessary Pages to disk, freeing space for new processes.
• Memory Protection: Through Segmented or Page-Based management, programs prevent unauthorized access to other processes or system resources.

File System

File System manages data storage and organization on disks, serving as a core interface between the operating system and users.

• Storage Structure: File systems organize files using a Directory Tree Structure, with each file containing data blocks, metadata (e.g., permissions, creation time), and Index Nodes.
• Access Control: Uses Permissions Bits (read, write, execute) to restrict user access to files, ensuring data security.
• Log Mechanism: Uses Log Files to record operation logs, ensuring data consistency recovery after system crashes.

Device Management

Device Management coordinates computer hardware resources, ensuring efficient and reliable input/output operations.

• Device Drivers: Operating systems communicate with hardware via Driver Programs, abstracting low-level details and providing a unified interface.
• I/O Scheduling: Reduces disk access latency through Buffer Pools and Caching Technologies, optimizing device throughput.
• Device Allocation: Dynamically allocates device resources to avoid waste while preventing multiple processes from simultaneously using the same device.

User Interface

User Interface is the bridge between the operating system and users, divided into Command-Line Interface (CLI) and Graphical User Interface (GUI).

• Command-Line Interface: Implements system operations via text commands (e.g., ls, cd), suitable for advanced users and script writing.
• Graphical User Interface: Provides visual windows, icons, and menus, lowering user operation barriers and improving interaction efficiency.
• Multi-Tasking Support: Through Taskbar and Window Managers, enables parallel operation of multiple windows and tasks.

Core Components of an Operating System

The operating system consists of multiple modules working collaboratively to form a complete functional system.

• Kernel (Kernel): As the core component, it handles hardware resources, process scheduling, and memory management.
• Shell: The command interpreter between users and the operating system, supporting script execution and system calls.
• System Call Interface: Provides standardized interfaces for applications to access operating system functions (e.g., fork(), open()).
• Driver: Handles communication with hardware devices, converting abstract system instructions into device-recognizable signals.