D386 WGU

Types of OSs: Single-user systems

multi-tasking, found in laptops and desktops

Mobile device OSs

for small hand-held devices like phones, tablets, e-readers

Mainframe systems

large-scale platforms and enterprise environments

Network server systems

designed for specific purpose like database or web server

Real-time systems

 Systems that need to act in real time; ie in pacemakers, cars

Embedded control systems

designed to control a single piece of equipment; ie thermostat

Distributed systems

geared toward allocating process power, programs files, etc to network users

Operating Systems handle:

* Disk storage and file management


* Device access
* Memory management
* Input/output
* Processor management

Drivers

 specific software that controls access to a particular piece of hardware

Application

software written to supplement the commands available to a particular OS

Version

a particular revision of software

Source

the high-level code that is written to produce software

Open-source

source code that can be examined and modified by anyoneClosed source

Closed source

only the owner and their designates can examine and modify

Shell

 a program that runs on the OS that allows the user to issue commands

Graphical User Interface (GUI)

a graphical interface for an operating system (i.e. the desktop in Windows)

Network

a group of computers that can communicate with each other

Cooperative multitasking

a method in which the application was responsible for giving up the processor (early versions of Windows worked like this)

Preemptive multitasking

a method in which the processor controls application access to itself

Multithreading

the ability of a single application to have multiple requests of the processor at one time

32-bit operating system, 64-bit OS

OSs that can run on 32-bit and 64-bit processors respectively

x86

group term to refer to operating systems that run on the Intel processor. Original Intel processors were identified with numbers that ended in 86

ARM

an operating system that can run on ARM processors. They use a RISC instruction set

Random Access Memory (RAM)

memory used by the operating system to run applications

Server

Allow for sharing of information and applications by workstation Oss

Workstation

Allow end users to access information on server machines

Mobile

used on mobile devices such as phones and tablets

Cloud-based

OS that is cloud-based. Personal data is stored on the cloud. Chrome OS is an example.

Common OSs

* Microsoft Windows


* MacOS
* Linux: free and open source. Created in 1991 by Linus Torvolds
* MS Windows Phone
* MS Windows Tablet
* Android
* iOS
* iPadOS
* ChromeOS

Operating System Life Cycle

Refers to the time when the OS is introduced to the time in which the OS is no longer supported

End-of-life (EOL)

OS will no longer receive updates

Life cycle terms

* Alpha


* Beta
* Release Candidate
* Current
* Service Pack
* Mainstream support
* Extended Support

Minimum System Requirements

* Memory


* CPU
* Architecture
* Storage
* Prerequisites
* Display
* Video RAM (VRAM)
* Licensing

Ways to install an OS

* Optical Disc (CD/DVD)


* ISO Mountable
* USB Drive
* Network Installation

Barebones Computer System

a system that can run only one program at a time with no memory or I/O.

OS provides 3 functions:

* Command services


* Program services
* Hardware services

Multitasking

A logical extension of multiprogramming. The CPU executes multiple processes by switching among them, but the switches occur frequently, providing the user with a fast response time.

Multiprogramming

Allows several jobs to be in memory at the same time, thus ensuring that the CPU always has a job to execute.

Concurrency

Exists when multiple threads are making progress

Bootstrapping

The first program to run on computer power-on which then loads the operating system.

Kernel

The operating system component running on the computer at all times after system boot.

Diskless workstation aka thin client

A term describing systems that have no local storage.

Interactive (aka conversational) system

Describes a type of computing that provides direct communication between the user and the system.

Batch processing

A method for giving commands to a computer in which commands are entered into files, and the files are executed, without any human interaction.

Application Programming Interface (API)

A set of commands, functions, and other tools that can be used by a programmer in developing a program.

Services of an OS (not all are in every OS)

* The user interface, command processor, and application program interface


* The file management system
* The input/output control system
* Process control management and interprocess communication
* Memory management
* Scheduling and dispatching
* Secondary storage management
* Network management, communication support, and communication interfaces
* System protection management and security
* Support for system administration.

Tasks of a sysadmin

* System configuration and setting group configuration policies


* Adding and deleting users
* Controlling and modifying user privileges to meet the changing needs of the users
* Providing and monitoring appropriate security
* Managing, mounting, and unmounting file systems
* Managing, maintaining, and upgrading networks
* Providing secure and reliable backups
* Providing and controlling software, installing new software, and upgrading software as required
* Patching and upgrading the operating systems and other system software
* Recovering lost data
* Tuning the system for optimum availability and performance
* Monitoring system performance and recommending system modifications and upgrades when necessary to meet user requirements.

Organization

Ring diagram with kernel in center and user level (or shell) surrounding it

Command interpreter (aka shell)

program that takes and processes user commands.

Types of shells

C-shell, Bourne-Again (aka bash) shell, Korn shell

Linux GUIs

K Desktop Environment (aka KDE), GNOME

System calls

a call from the user level to the kernel level typically for a protected operation such as for memory or process management

Types of system calls

* Process control


* File management
* Device management
* Information maintenance
* Communications
* Protection

Application Programming Interface (API)

set of functions that are available to use a resource (such as a kernel)

Categories of system services

* File management


* Status information
* File modification
* Programming-language 
* Program loading and execution
* Communications
* Background services

Linkers

link parts of a program together

Loaders

 load those parts into memory so the program can be run

DRAM (dynamic random access memory)

The common version of RAM, which features high read and write speeds.

ADRAM

Asynchronous DRAM

FPM DRAM

fast page mode DRAM)

EDO DRAM

extended data out DRAM

BEDO DRAM

burst EDO DRAM

SDRAM

synchronous DRAM

SDR SDRAM

single data rate SDRAM

DDR SDRAM

double data rate SDRAM

DDR2 SDRAM

double data rate, version two, SDRAM

DDR3 SDRAM

double data rate, version three, SDRAM

DDR4 SDRAM

double data rate, version four, SDRAM

DDR5 SDRAM

double data rate, version five, SDRAM

SRAM

static random access memory

ROM

read-only memory

Hard Disk Drive (HDD) System parts

* Controller


* Hard Disk
* Host Bus Adapter

Hard Disk Drive (HDD) parts

* Platters


* Read/write heads
* Tracks
* Sectors
* Cylinders
* Clusters (allocation units)

Solid-State Drives (SSDs) Advantages over HDDs

* Faster start-up and read times


* Less power consumption and heat produced
* Silent operation
* Generally more reliable because of a lack of moving parts
* Less susceptible to damage from physical shock and heat production
* Higher data density per square centimeter

Solid-state hybrid drive (SSHD)

OS sees an SSHD as single drive

Dual-drive storage solution

Implemented and seen by OS as two separate drives

SSD Communication Interfaces

* SATA


* PCIe
* NVMe

SSD Form Factors (describes the shape and size of a device)

* mSATA


* M.2

Removable storage and media

* Flash memory


* USB flash drives
* SD and other memory cards
* Hot-swappable devices: means that you can insert and remove device when system is powered on
* Optical Drives (CD/DVD)

A CPU is often viewed as 3 parts

* Arithmetic logic unit (ALU)


* Control unit (CU)
* Interface unit

Word

 the length of a command in the system. Typical 32- or 64-bits long (which defines whether the machine is 32- or 64-bits)

Read-only memory (ROM)

used to boot the program

Registers

* Memory Address Register (MAR)


* Memory Data Register (MDR)

Reliability

The chance that some disk out of a set of N disks will fail is much greater than the chance that a specific single disk will fail.

Redundancy

The solution to the problem of reliability. Stores extra information that is not normally needed but can be used in the event of disk failure to rebuild the lost information.

Mean time between failures (MTBF)

The statistical mean time that a device is expected to work correctly before failing.

bit-level striping

The splitting of data at the bit level, with each bit in a byte or word stored on a separate device.

block-level striping

The splitting of data at the block level, with each block stored on a separate device.

Problems with RAID

Unfortunately, RAID does not always assure that data are available for the operating system and its users.

CPU:

Made of ALU and CU

Fetch-Execute Instruction Cycle

The CPU reads instructions from main memory during the instruction-fetch cycle

Classification of instructions

\
* Data movement (LOAD, STORE, etc)


* Arithmetic
* Boolean logic
* Single operand manipulation
* Bit manipulation
* Shift and rotate
* Program control
* Stack
* Multiple Data

CPU Architectures

* CISC


* RISC

CISC - complex instruction set computers

 supports array

RISC - reduced instruction set computers

does not support an array

CPU Features and enhancements

* Fetch-execute timing issues (clock issues)


* Improvements for CPU performance
* Pipelining


* Scalar and Superscaler processor organization
* Out‐of‐Order Processing
* Branch Instruction Processing

Memory enhancements

* Wide path memory access


* Memory interleaving
* Cache memory

Virtual Machine Manager (VMM) or Hypervisor

These operating systems are installed and run directly on top of a computer's hardware and are often referred to as “bare metal”

Type 1 or nativ hypervisor

software that interfaces directly with the computer hardware for specialized devices like a car

Type 2 or hosted hypervisor

software that runs as a program on a standard operating system & virtual machine works through an operating system vmware, application on the operating system