Types of Operating Systems

Single-User Single-Tasking Operating Systems: Allow one user to perform one task at a time (e.g., MS-DOS)
Single-User Multi-Tasking Operating Systems: Allow one user to perform multiple tasks simultaneously (e.g., Windows 95)
Multi-User Single-Tasking Operating Systems: Allow multiple users to perform one task at a time (e.g., older versions of Unix)
Multi-User Multi-Tasking Operating Systems: Allow multiple users to perform multiple tasks simultaneously (e.g., modern versions of Unix, Windows NT)

Kernel: Manages hardware resources and provides services to applications
Device Drivers: Manage communication between hardware devices and the operating system
System Libraries: Provide interfaces for applications to access operating system services
System Utilities: Perform maintenance and management tasks (e.g., disk formatting, backups)

Process: A program in execution
Process States:
- Newborn: Process created
- Ready: Process waiting for CPU time
- Running: Process executing on CPU
- Waiting: Process waiting for I/O or other event
- Zombie: Process terminated, but parent process not notified
Process Scheduling: Allocates CPU time to processes (e.g., First-Come-First-Served, Shortest Job First, Priority Scheduling)

Memory Hierarchy: Organization of memory levels from fastest to slowest (e.g., registers, cache, main memory, disk storage)
Memory Allocation: Assigns memory to processes (e.g., contiguous allocation, paging, segmentation)
Virtual Memory: Provides more memory than physically available (e.g., using disk storage)

File System Types:
- Local File Systems: Store files on local devices (e.g., FAT, NTFS)
- Network File Systems: Store files on remote devices (e.g., NFS, SMB)
File System Operations: Create, delete, read, write, and manage files and directories
File System Structure: Organization of files and directories (e.g., hierarchical, flat)

Security Threats: Unauthorized access, viruses, worms, Trojans
Security Mechanisms:
- Authentication: Verifies user identity (e.g., passwords, biometrics)
- Authorization: Grants access to resources based on user identity and permissions
- Access Control: Controls access to resources based on permissions and access control lists (ACLs)

Single-User Single-Tasking: Operates on one user executing a single task (e.g., MS-DOS).
Single-User Multi-Tasking: Facilitates a single user performing multiple tasks at the same time (e.g., Windows 95).
Multi-User Single-Tasking: Supports several users but only one task per user at any given time (e.g., older Unix versions).
Multi-User Multi-Tasking: Allows multiple users to execute several tasks concurrently (e.g., modern Unix, Windows NT).

Kernel: Core component responsible for hardware management and application services.
Device Drivers: Software that facilitates interaction between hardware devices and the operating system.
System Libraries: Collections of routines that provide application interface to operating system functions.
System Utilities: Tools that perform system maintenance and operational tasks like disk formatting and backups.

Process: The active execution instance of a program.
Process States:
- Newborn: The phase when a process is created.
- Ready: The process is prepared and waiting for CPU allocation.
- Running: The process currently executing on the CPU.
- Waiting: The process is in a hold state, waiting for input/output or another event.
- Zombie: A completed process that has not yet been acknowledged by its parent process.
Process Scheduling: Mechanisms to assign CPU time to processes; methods include First-Come-First-Served, Shortest Job First, and Priority Scheduling.

Memory Hierarchy: Ranks memory types from fastest to slowest, including registers, cache, main memory, and disk storage.
Memory Allocation: Strategies for distributing memory among processes, such as contiguous allocation, paging, and segmentation.
Virtual Memory: A memory management capability that allows the system to utilize disk storage to provide more memory than what is physically available.

File System Types:
- Local File Systems: Manage files on local storage devices (e.g., FAT, NTFS).
- Network File Systems: Handle files on remote servers (e.g., NFS, SMB).
File System Operations: Basic actions involving files and directories including creation, deletion, reading, and writing.
File System Structure: Organizational methods for files and directories, typically hierarchical or flat in design.

Security Threats: Risks to system integrity such as unauthorized access, viruses, worms, and Trojans.
Security Mechanisms:
- Authentication: The process of confirming user identity via methods like passwords or biometrics.
- Authorization: The process that determines user access to certain resources based on their identity and designated permissions.
- Access Control: Mechanisms that regulate resource access based on set permissions and access control lists (ACLs).