Operating Systems Overview

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Study Notes

Windows OS is user-friendly and compatible with various software; popular versions include Windows 10 and Windows 11.
Mac OS is designed for Apple devices, known for its sleek design, high security, and Apple product integration; examples include macOS Monterey and macOS Ventura.
Linux OS is open-source, customizable, and secure; popular distributions include Ubuntu, Fedora, and Debian.
Android OS is the most widely used mobile operating system, open-source, and with a vast app ecosystem; examples include Android 12 and Android 13.
iOS is secure and high-performance, used exclusively on Apple mobile devices; versions include iOS 15 and iOS 16.
Unix is a multi-user, multitasking operating system known for its security and stability; widely used in research and enterprise environments.
Chrome OS is lightweight and cloud-centric, designed for Chromebooks, focusing on web-based applications and simplicity.
Solaris is an enterprise-class operating system known for scalability, security, and performance in high-end servers.
Fedora is a Linux-based operating system favored by developers and system administrators for its focus on open-source software, cutting-edge features, and robust security.
Embedded Linux is a version of Linux used in embedded systems like smart TVs, routers, and IoT devices.

New: Process is being created
Ready: Process is ready to run and waiting for CPU time.
Running: Process is currently being executed by the CPU.
Waiting (Blocked): Process is waiting for an event to complete (like I/O operations).
Terminated: Process has finished execution.

Process can terminate normally (completing execution) or abnormally (error or external intervention).
OS deallocates resources associated with the process after termination.
Process creation can occur when:
- A user starts a program
- An existing process creates a new process
- The OS needs to create a system process

Smallest unit of execution within a process.
A process can have one or more threads (multithreading) for specific tasks.
Each thread executes independently but shares the same memory space with other threads in the process.
Threads within a process share resources like memory but have separate stacks and program counters.
Single-threaded processes have one thread executing one task at a time.
Multi-threaded processes have multiple threads within the same process, enabling parallelism and efficient CPU usage.

Decides which process or thread runs on the CPU at any given time.
Types of Schedulers:
- Long-Term Scheduler (Job Scheduler): Determines which processes are admitted into the ready queue. Controls the degree of multiprogramming (number of processes in memory).
- Short-Term Scheduler (CPU Scheduler): Selects the next process from the ready queue to run on the CPU; done frequently as processes run in short bursts.
- Medium-Term Scheduler: Temporarily removes processes from memory.