2.1 CS

Operating system (OS)

System software that manages hardware resources and provides services for applications

Memory management

Controls allocation and deallocation of RAM to processes and manages memory usage efficiently

Virtual memory

Uses secondary storage as an extension of RAM when physical memory is full

Advantages of virtual memory

Allows larger programs to run and reduces chance of running out of RAM

Disadvantages of virtual memory

Slower than RAM, reducing overall system performance

Processor scheduling

Controls how CPU time is allocated to processes

Multitasking

Running multiple processes apparently at the same time by rapidly switching between them

Interrupt

A signal that causes the CPU to pause current execution to deal with an event

Interrupt Service Routine (ISR)

A routine executed to handle an interrupt before returning to the previous process

Device driver

Software that allows the operating system to communicate with hardware devices

BIOS

Basic Input/Output System that performs hardware checks and starts the boot process

Role of BIOS

Performs POST and loads the operating system into memory during startup

First Come First Served (FCFS) scheduling

Processes are executed in the order they arrive; simple but can cause long waiting times

Shortest Job First (SJF) scheduling

Processes with the shortest execution time are run first; reduces average waiting time but may starve long processes

Round Robin scheduling

Each process is given a fixed time slice (quantum) and rotated; ensures fairness and supports multitasking

Embedded operating system

An OS designed for dedicated devices with specific functions and limited resources

Real-time operating system (RTOS)

An OS that guarantees responses to inputs within strict time limits

Hard real-time system

System where missing a deadline leads to system failure (e.g. airbag system)

Soft real-time system

System where missing a deadline is undesirable but not catastrophic (e.g. video streaming)

Why RTOS are used

Used in safety-critical systems where timing accuracy is essential

Distributed operating system

Manages multiple networked computers so they appear as a single system

Multi-user operating system

Allows multiple users to access and use a system simultaneously

Virtual machine

A software-based emulation of a computer system that runs an operating system inside another OS