Operating System (OS) Overview

• Operating System (OS) Overview

Introduction to Operating System

• An Operating system is a program that manages computer hardware.
• It provides a basis for application programs.
• It acts as an intermediary between the user and the computer hardware.
• An Operating system is software that performs basic tasks; file management, memory management, process management, handling I/O, and controlling peripheral devices.
• The OS is a vital component of the system software in a computer system.
• Popular OS include Linux, Windows, and VMs.
• An operating system acts as an interface between the user and the computer hardware and controls the execution of all kinds of programs.

Computer System Components

• A Computer System contains hardware like the CPU, memory, and I/O devices.
• Input devices provide data input to the processor, which generates useful information through output devices.
• Input is stored in the computer's memory.

Role of Operating System

• Memory management.
• Processor management.
• Device management.
• File management.
• Security.
• Control over system performance.
• Job accounting.
• Error detecting.

Memory Management

• Memory Management refers to the management of Primary Memory or Main Memory.
• Main memory provides fast storage to be accessed by the CPU for a program to be executed.
• An OS keeps track of primary memory, i.e., parts in use and by whom, and parts not in use. The OS decides which process will get memory and how much (in multiprogramming).
• The OS allocates memory when a processor requests it.
• The OS de-allocates the memory when a processor no longer needs it or has been terminated

Processor Management

• In multiprogramming, the OS decides which process gets the processor and for how much time. This is also known as process scheduling.
• An OS keeps track of the processor and the status of processes and the program responsible (traffic controller).
• The OS allocates the processor to a process.
• The OS de-allocates the processor when a process is no longer required.

Device Management

• An OS manages device communication via their respective drivers.
• The OS keeps track of all devices, and the program responsible for the task is known as the I/O controller.
• The OS decides which process gets the device when and for how much time.
• The OS allocates the device in an efficient way
• The OS de-allocates devices

File Management

• A file system is normally organized into directories for easy navigation and usage.
• Directories may contain other files and even other directories.
• An OS keeps track of information, location, uses, and status. The collective facilities are often known as a file system.
• The OS decides who gets the resources.
• The OS allocates the resources.
• The OS de-allocates the resources.

Security

• By means of passwords and other similar techniques, the OS provides prevention against unauthorized access to programs and data.

Control over System performance

• Recording delays between a request for service and the system's response to it.

Job Accounting

• The OS keeps track of time and resources used by various jobs and users

Error Detecting

• The OS generates production dumps, traces, error messages, and other debugging and error-detecting aids.

Types of Operating Systems

• Batch Processing OS.
• Multiprogramming system.
• Multitasking OS.
• Time shared OS.
• Multiprocessor system.
• Cluster system.
• Distributed system.
• Real-Time system.
• Open-source OS.
• Mobile OS.

Batch Processing Operating Systems

• Batch processing is a technique where an OS collects programs and data together in a batch before processing starts.
• The OS defines a job with a predefined sequence of commands, programs, and data as a single unit.
• The OS keeps several jobs in memory and executes them without manual intervention Jobs are processed in order of submission, i.e., first come, first served.
• When a job completes its execution, its memory is released, and the output for the job gets copied into an output spool for later printing or processing.

Multiprogramming Systems

• Multiprogramming increases CPU utilization by organizing jobs so that the CPU always has one to execute.
• The OS keeps several jobs in memory at a time.
• This set of jobs is a subset of those kept in the job pool.
• The OS picks and begins to execute one of the jobs in memory.
• A Multiprogramming OS monitors the state of all active programs and resources to ensure the CPU is never idle unless there are no jobs to process.

Multitasking Operating Systems

• Multitasking occurs when multiple jobs are executed by the CPU simultaneously by switching between them.
• A multitasking OS is also known as a time-shared OS (which uses the concept of CPU scheduling and multiprogramming to provide each user with a small portion of time-shared CPU).
• The OS allows users to share the computer simultaneously.
• Since each action or command in a time-shared system tends to be short, very little CPU time is needed for each user. As the system switches CPU rapidly, each user gets the impression that it is their own CPU.

Time-Shared Operating Systems

• Time-sharing is a technique that enables many people, located at various terminals, to use a particular computer system simultaneously.
• The Operating system uses CPU scheduling and multiprogramming to provide each user with a small portion of time.
• Computer systems that were primarily batch systems have been modified to time-sharing systems.

Multiprocessor Operating Systems

• Multiprocessor or parallel systems have multiple processors working in parallel that share the computer clock, memory, bus, and peripheral devices.
• There are two types of multiprocessors, symmetric and asymmetric.
• In symmetric multiprocessors, each processor contains a similar copy of the OS and communicates with each other in a peer-to-peer relationship.
• In asymmetric multiprocessors, Master processor gives instruction to all the other processors and has a contains master slave relationship.

Cluster Systems

• Cluster systems are similar to parallel systems as both have multiple CPUs.
• Clustered systems are created by merging two or more individual computer systems.
• Clustered systems have independent computer systems with a common storage that work together by combining hardware for disks and software.
• Two types of clustered systems exist:
• Asymmetric; one server is in hot standby mode.
• Symmetric; where the nodes run applications and monitor each other

Distributed Operating Systems

• Distributed systems use multiple central processors to serve multiple real-time applications and multiple users
• Data processing jobs are distributed among the processors.
• The processors communicate through various communication lines such as high-speed buses or telephone lines.
• Processors can vary in function and size.
• Processors are also referred to as sites, nodes, or computers.

Real-Time Operating Systems

• These types of OS serve real time systems.
• The interval required to process and respond to input is very small.
• Are used when rigid time requirements exist on a processor operation
• Can be used as a control device in a dedicated application.
• e.g., Scientific experiments, industrial control systems, air traffic control systems, robots, and weapon systems.
• Two types of real-time OS exist:
• Hard real-time systems with strict time constraints.
• Soft real-time systems with less strict time constraints.

Open Source Operating Systems

• They are released under a license where the copyright holder allows others to study, change, and distribute software-
• This can be done for any reason.
• Examples of open-source OS are Cosmos, FreeDOS, Genode, and Ghost OS.

Mobile Operating Systems

• These operating systems help to run other application software on mobile devices.
• They are the same kind of software as computer operating systems (Linux and Windows) but are light and simple.
• Popular platforms: Android OS, Bada (Samsung Electronics), BlackBerry OS, iPhone OS / iOS, Symbian OS, Windows Mobile OS, Harmony OS, Palm OS, and WebOS (Palm/HP).

Overview of operating systems (OS), which manage computer hardware and act as an intermediary between users and hardware. Covers computer system components like CPU, memory, and I/O devices. Explains the role of OS in memory management.