Operating Systems
Operating Systems
Operating Systems (OS) are essential software that manage computer hardware and software resources, providing a platform for applications to run. Here are some key concepts:
Batch OS – Processes jobs in batches without user interaction (e.g., early IBM mainframes).
Time-Sharing OS – Multiple users can interact with the system simultaneously (e.g., UNIX).
Distributed OS – Manages multiple machines as a single system (e.g., Google File System).
Real-Time OS (RTOS) – Ensures quick response time for critical applications (e.g., VxWorks, QNX).
Embedded OS – Designed for embedded systems like IoT devices (e.g., FreeRTOS).
Mobile OS – Used in smartphones (e.g., Android, iOS).
Process Management – Handles creation, scheduling, and termination of processes.
Memory Management – Allocates and deallocates memory for programs.
File System Management – Manages data storage, retrieval, and permissions.
Device Management – Controls input/output operations and hardware communication.
Security & Access Control – Protects data from unauthorized access.
User Interface – Provides CLI (Command Line Interface) or GUI (Graphical User Interface).
Process States – New, Ready, Running, Waiting, Terminated.
CPU Scheduling – FCFS, SJF, Round Robin, Priority Scheduling.
Process Synchronization – Semaphores, Mutexes.
Deadlocks – Prevention, Avoidance, Detection, Recovery.
Paging & Segmentation – Divides memory for efficient allocation.
Virtual Memory – Uses disk as an extension of RAM.
Memory Allocation – Contiguous and Non-Contiguous (e.g., Paging).
Directory Structures – Single-Level, Two-Level, Hierarchical.
File Allocation Methods – Contiguous, Linked, Indexed.
File Permissions – Read, Write, Execute.
Interrupt Handling – Manages hardware-generated signals.
DMA (Direct Memory Access) – Improves data transfer efficiency.
Spooling – Queues jobs for peripheral devices.
Authentication & Authorization – User identification and permissions.
Access Control Lists (ACLs) – Defines permissions for files and resources.
Encryption & Firewalls – Data security mechanisms.