Overview of Operating Systems

Overview of Operating Systems

• An Operating System (OS) acts as an interface between users and computer hardware.
• Responsible for managing files, memory, processes, input/output functions, and peripheral devices.
• Common examples of operating systems include Linux, Windows, VMS, OS/400, AIX, and z/OS.

Key Functions of an Operating System

• Memory Management: Oversees primary memory, allocates and de-allocates memory for processes.
• Processor Management: Controls process scheduling and allocates CPU time to processes.
• Device Management: Manages peripheral devices and facilitates communication between them and the system.
• File Management: Organizes and maintains file systems and data storage.
• Security: Ensures proper access controls and user authentication.
• Performance Control: Monitors and optimizes system performance.
• Job Accounting: Keeps track of resource usage for billing or administrative purposes.
• Error Detection: Identifies and manages operational errors.
• Coordination: Facilitates interaction between software and users.

Memory Management

• Involves tracking memory usage, allocating memory to processes, and freeing up memory when no longer needed.
• Essential for enabling efficient execution of applications by storing them in main memory.

Processor Management

• In multiprogramming environments, the OS manages CPU allocation and process scheduling to ensure efficient CPU utilization.
• The system may enter idle states due to slower I/O operations compared to CPU speed.

Time-Sharing Operating Systems

• Allow multiple users to access a computer system simultaneously through rapid time-sharing of CPU resources.
• Aims to minimize response time for user requests compared to maximizing processor usage as in batch systems.
• Advantages include quick responses and reduced CPU idle time; disadvantages involve reliability and data security concerns.

Distributed Operating Systems

• Comprised of multiple processors that communicate through communication lines; allows for resource sharing among multiple users.
• Offers advantages like redundancy (if one site fails, others may continue) and improved customer service.

Network Operating Systems

• Operate on servers to manage data, users, and applications within a network, allowing shared access to files and printers.
• Examples include Windows Server and UNIX; advantages include centralized security and stability, while disadvantages include high costs and dependency risks.

Real-Time Operating Systems

• Designed for applications requiring immediate response, suitable for environments with strict timing constraints.
• Used in critical areas like air traffic control and medical imaging.

Multiprogramming

• Allows multiple programs to reside in memory simultaneously to enhance CPU usage.
• Involves job monitoring and scheduling to ensure the CPU is always engaged.

Interactivity

• Focuses on user engagement with the OS through interfaces that manage input devices for user command input.

Device-Independent I/O Software

• Provides a uniform interface for diverse devices, performing I/O functions common across devices.
• Functions include device protection, error reporting, and buffering.

User-Space I/O Software

• Libraries (like stdio in C) that facilitate simplified access to kernel functionalities and device interactions.

Kernel I/O Subsystem

• Manages scheduling and buffering of I/O requests to optimize efficiency and improve response times across applications.
• Maintains buffers to handle discrepancies in data transfer speeds between devices and applications.