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Unit 3: Operating Systems - Coggle Diagram
Unit 3: Operating Systems
OS Overview
manages each and every piece of hardware and software
controls every file, device, section of main memory, and processing time
controls the execution of application programs and acts as an interface between applications and the hardware
2 objectives
Convenience: an OS makes a computer more convenient to use
Efficiency: an OS allows the computer resources to be used in an efficient manners
a set of programs that coordinate all the activities in a computer
Services
• Program creation – provides a variety of facilities and services to assist programmers in creating programs
• Program execution – prepare resources, load instructions and data into main memory, initialize devices and files, and perform a number of steps to be executed
• Access to I/O devices – handles the instructions/control signals for each I/O device’s operations
• Controlled access to file – handles the access based on I/O device nature and file format on storage medium, as well as protection mechanism
OS Components
5 major components
Memory Manager
Processor Manager
Device Manager
File Manager
Network Manager
a component that is unique to each OS
Users issue commands to the OS through the UI
There may be different versions of UI within the same OS
manager works closely with other managers and perform its unique roles
• Work harmoniously with other managers
• Need active cooperation from all manager
manager must perform the following tasks
• Monitor its resources continuously
• Enforce the policies that determine who gets what, when, and how much
• Allocate the resource when appropriate
• Deallocate the resource when appropriate
User interface
• Users interact directly with the OS through the UI
• UI used to consist of command lines
• Now most UIs are graphical in nature - GUI
• UI varies from one OS to another
Cooperation
The Device Manager (DM) receives the electrical impulses from the keyboard/mouse, forms the command, and sends the command to the UI, where the Process Manager (PM) validates the command
The PM sends an acknowledgement message to be displayed on the screen so the user knows that the command has been sent
When the PM receives the command, it checks whether the program must be retrieved from storage, or is already in memory, and then notifies the appropriate manager
OS Functions
Providing a user interface
UI controls how users enter data and instructions, and how information is displayed on the display
2 types of common Ul
• Graphical UI
• Command line
NUI (natural UI)
• Touch screen
• Gesture recognition
• Speech recognition
• VR (simulations)
Managing programs and processes
• Multitasking OS
• Two or more programs may reside in memory at the same time and these programs can run concurrently
Foreground
Background
• Processes are programs/routines that provide support to other programs or hardware
• Single user vs multi-users OS
OS Types
three basic categories of OS on computers and mobile devices
Desktop OS
Mobile OS
Server OS
Complete OS that works on desktops
and laptops
Windows, macOS and UNIX are
proprietary software
Linux is open-source software
A multiuser OS that organizes and coordinates how multiple users access and share resources on a network
A server is a computer dedicated to providing services to other computers or devices on a network
• Storing contents
• Controlling access to hardware, software, other resources on a network
• Can support from two to several thousand connected computers and devices simultaneously