Overview of Operating Systems

Definition: Software that manages computer hardware and software resources and provides common services for computer programs.
Purpose: Acts as an intermediary between users and the computer hardware.

Process Management:
- Handles creation, scheduling, and termination of processes.
- Manages CPU scheduling and multitasking.
Memory Management:
- Allocates and deallocates memory space as needed.
- Keeps track of each byte in a computer’s memory through paging and segmentation.
File System Management:
- Manages files on disk drives, including reading/writing and access control.
- Organizes files into directories for easier navigation.
Device Management:
- Manages device communication via drivers.
- Controls input and output operations to peripheral devices.
User Interface:
- Provides a way for users to interact with the computer (command-line or graphical user interface).

Batch Operating Systems:
- Processes batches of jobs without user interaction.
- Example: Early IBM mainframes.
Time-Sharing Operating Systems:
- Allows multiple users to access the system simultaneously.
- Example: UNIX.
Distributed Operating Systems:
- Manages a group of distinct computers and makes them appear as a single coherent system.
- Example: Google’s Android.
Real-Time Operating Systems (RTOS):
- Processes data as it comes in, typically used in embedded systems.
- Example: VxWorks.
Network Operating Systems:
- Provides services to computers connected over a network.
- Example: Windows Server.

Kernel: Core component of an OS, manages system resources, and communication between hardware/software.
User Mode & Kernel Mode:
- User Mode: Restricted mode for user applications.
- Kernel Mode: Privileged mode for executing OS code.
System Calls: Interfaces through which user programs request services from the OS.

Windows: Widely used in personal computers and enterprise settings; user-friendly interface.
Linux: Open-source, highly customizable, popular for servers and development.
macOS: Developed by Apple, known for its sleek interface and integration with Apple hardware.
Android: Based on Linux, widely used in mobile devices.

Access Control: Mechanisms to restrict access to files and processes.
Authentication: Verifying user identity (passwords, biometrics).
Malware Protection: Tools and techniques to guard against malicious software.

Virtualization: Running multiple OS instances on a single hardware platform.
Cloud Computing: OS services delivered over the internet, enhancing scalability and accessibility.
Mobile Operating Systems: Focus on touch interfaces and energy efficiency.

Software that manages hardware and software resources, facilitating interaction between users and computer hardware.

Process Management:
- Responsible for creating, scheduling, and terminating processes; ensures efficient CPU utilization and multitasking.
Memory Management:
- Allocates memory as needed and tracks usage through methods like paging and segmentation.
File System Management:
- Handles file operations such as reading/writing and access control, organizing files into directories for user convenience.
Device Management:
- Manages interactions with hardware devices via drivers, overseeing input and output operations for peripherals.
User Interface:
- Provides a platform for user interaction with the system, which can be command-line or graphical.

Batch Operating Systems:
- Processes jobs in batches without user intervention, typical in early computing environments like IBM mainframes.
Time-Sharing Operating Systems:
- Allows concurrent access for multiple users, optimizing resource sharing; an example is UNIX.
Distributed Operating Systems:
- Manages a cluster of independent computers, presenting them as a unified system, such as Google’s Android.
Real-Time Operating Systems (RTOS):
- Handles immediate data processing, common in embedded systems; an example is VxWorks.
Network Operating Systems:
- Offers services and connectivity for networked computers, exemplified by Windows Server.

Kernel:
- The OS’s core component that manages system resources and facilitates communication between hardware and software.
User Mode & Kernel Mode:
- User Mode restricts user applications; Kernel Mode provides privileges to execute OS code.
System Calls:
- Interfaces for user applications to request services from the operating system.

Windows:
- Dominant in personal and enterprise computer markets with a user-friendly interface.
Linux:
- Open-source, customizable, and preferred for server environments and software development.
macOS:
- Apple’s OS known for aesthetic design and seamless integration with Apple devices.
Android:
- Mobile OS based on Linux that enjoys widespread use in smartphones and tablets.

Access Control:
- Mechanisms to limit access to files and processes based on user permissions.
Authentication:
- User identity verification using methods like passwords and biometric systems.
Malware Protection:
- Tools and strategies designed to prevent and counteract malicious software threats.

Virtualization:
- Allows multiple operating system instances to run on a single hardware setup, maximizing resource utilization.
Cloud Computing:
- Provides OS services over the internet, promoting flexibility and scalability for users.
Mobile Operating Systems:
- Designed for touch interactions and energy efficiency, catering to the mobile device market.