> For the complete documentation index, see [llms.txt](https://hanfak.gitbook.io/workspace/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hanfak.gitbook.io/workspace/operating-system.md).

# Operating Systems

Information about using

* Linux
* Bash
* Scripting
* etc

## What is an Operating System?

* An Operating System (OS) is a collection of software that manages computer hardware and provides services for programs.
  * it hides hardware complexity,
  * manages computational resources
  * provides isolation and protection.
  * it directly has privilege access to the underlying hardware.
* Major components of an OS are
  * the file system
  * scheduler
  * device driver.
* three key elements of an operating system
  * (1) Abstractions (process, thread, file, socket, memory)
  * (2) Mechanisms (create, schedule, open, write, allocate)
  * (3) Policies (LRU, EDF)
* two operating system design principles
  * (1) Separation of mechanism and policy by implementing flexible mechanisms to support policies
  * (2) Optimization for common case:
    * Where will the OS be used?
    * What will the user want to execute on that machine?
    * What are the workload requirements?
* three types of Operating Systems commonly used nowadays.
  * Monolithic OS
    * where the entire OS is working in kernel space and is alone in supervisor mode.
  * Modular OS
    * in which some part of the system core will be located in independent files called modules that can be added to the system at run time.
  * Micro OS
    * where the kernel is broken down into separate processes, known as servers. Some of the servers run in kernel space and some run in user-space.

## Concepts of Operating systems

* Processes and Process Management
* Threads and Concurrency
* Scheduling
* Memory Management
* Inter-Process Communication
* Input/Output Management
* Virtualization
* Distributed File Systems
* Distributed Shared Memory
* Cloud Computing