💻 Operating Systems Concepts
What is an Operating System?
An Operating System (OS) acts as an intermediary between the user and the computer hardware, managing resources and facilitating user interactions.
Types of Operating Systems:
- Batched OS
- Real-Time OS
- Time-Sharing OS
- Distributed OS
- Multiprogrammed OS
Basic Functions of an OS:
- Resource Allocation
- Program Control to Prevent Errors
What is the Kernel?
The kernel is the core of an OS, providing essential services to all parts of the operating system.
What is a Process?
A process is the execution of a program, categorized into:
- OS Process
- User Process
States of a Process:
Processes transition through the following states:
- New → Ready → Running → Waiting → Terminated
- Create → Admitted → Interrupt/Dispatch → I/O → Exit
What is Starvation and Aging?
- Starvation: A resource management issue where a process waits indefinitely for resources.
- Aging: A technique to avoid starvation by gradually increasing the priority of waiting processes.
What happens during a dead lock?
In a deadlock, processes get stuck waiting for each other’s resources and can’t move forward. This causes everything to come to a halt.
What is a Semaphore?
A semaphore is a variable used for controlling access to common resources.
Types:
- Binary Semaphore
- Counting Semaphore
What is Context Switching?
Context switching transfers control from one process to another, involving saving and loading the process states.
What is a Thread?
A thread is a lightweight process, a basic unit of CPU utilization comprising:
- Thread ID
- Program Counter
- Register Set
- Stack
What is Process Synchronization?
Process synchronization ensures only one process manipulates shared data at a time, avoiding race conditions.
What is Cache Memory?
Cache memory is a fast-access memory where the microprocessor first looks for data before accessing RAM.
Memory hierarchy:
- Registers → L1 Cache → L2 Cache → RAM → Secondary Memory
What is Virtual Memory?
Virtual memory allows secondary storage to function as main memory.
Benefits:
- No need for physical address management
- Each process has a virtual-to-physical address mapping
Logical vs Physical Address Space:
- Logical Address: Size of the process (virtual space)
- Physical Address: Size of the main memory
Compiler vs Interpreter:
- Compiler: Translates code into machine code before execution.
- Interpreter: Translates code line-by-line during execution.
Definitions:
- Throughput: Number of processes completed per time unit.
- Turnaround Time: Time taken to execute a process.
- Waiting Time: Time spent in the ready queue.
- Response Time: Time between a request and the start of the response.
What is a Real-Time System?
A real-time system processes data as it comes with strict time constraints, ensuring prompt responses to events.
Long-Term vs Short-Term Schedulers:
- Long-Term Scheduler (LTS): Loads processes into memory from the job queue.
- Short-Term Scheduler (STS): Allocates CPU to processes from the ready queue.
What is a Distributed System?
A distributed system operates in a network, sharing resources and communication between multiple systems.
What is a Daemon?
A daemon is a background program that runs without user input, typically in Unix or Linux systems, managing resources and automating tasks.
What is Busy Waiting?
Busy waiting occurs when a process repeatedly checks for a condition to be met before continuing execution.
Dual-Mode Operation:
- User Mode
- Kernel Mode
Path Types:
- Absolute Path: The exact path from the root directory.
- Relative Path: A path relative to the current location.
What is DRAM?
Dynamic RAM (DRAM) stores data as electrical capacitance, while Static RAM (SRAM) stores data as voltage levels.