Operating Systems

Operating Systems

Dasun Hegoda
Software Engineer

What we are going to talk
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Why Learn Operating Systems

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Operating System Definitions

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Types Of Operating Systems

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OS Functions/Features

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Buzzwords : Virtual Memory, File Allocation Table, Buffer
Work, Device Driver, System requirements, Kernel,
Command-line

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Key Players : Windows, Mac, Linux

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Comparison

What we are going to talk – Part 2
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Mobile Operating System

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Android

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iOS

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Comparison

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How To Choose, What To Choose

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Quiz

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Wrap Up

Why Learn Operating Systems
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OS is a key part of a computer system

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To understand how computers work under the hood

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To learn about system design eg: HW & SW as behavior of
OS affects entire machine
Understand large and complex system
OS Knowledge is applied across many areas eg:
Programming languages, Software development,
Algorithms

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To Learn trade offs between performance and functionality

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For your Course Requirement!!!

Operating System Definitions

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An operating system (OS) is a collection of software that
manages computer hardware resources and provides
common services for computer programs.
Microsoft Windows, Apple OS x, Linux, Android, iOS,
Windows Mobile
Application programs usually require an operating system
to function.
Operating system acts as an intermediary between
programs and the computer hardware.

Types Of Operating Systems

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Real-time

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Multi-user vs. Single User

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Multi-Tasking vs. Single-Tasking

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Distributed

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Embedded

1. Real-Time OS
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Multitasking operating system that aims at executing realtime applications.
Real-time operating systems are used to control
machinery, scientific instruments and industrial systems.
The main objective of real-time operating systems is their
quick and predictable response to events.
They have an event-driven or time-sharing design and
often aspects of both. An event-driven system switches
between tasks based on their priorities or external events
while time-sharing operating systems switch tasks based
on clock interrupts.

2. Multi-User OS
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Multiple users to access a computer system at the same
time.
Time-sharing systems and Internet servers can be
classified as multi-user systems as they enable multipleuser access to a computer through the sharing of time.
Single-user operating systems have only one user but may
allow multiple programs to run at the same time.

3. Multi-Tasking vs. Single-Tasking
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More than one program to be running at the same time,
from the point of view of human time scales.
A single-tasking system has only one running program.
Multi-tasking can be of two types: pre-emptive and cooperative.
Unix-like operating systems such as Solaris and Linux
support pre-emptive multitasking.
Mac OS prior to OS X used to support cooperative
multitasking.

4. Distributed
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Manages a group of independent computers and makes
them appear to be a single computer.
The development of networked computers that could be
linked and communicate with each other gave rise to
distributed computing.
Distributed computations are carried out on more than one
machine. When computers in a group work in cooperation,
they make a distributed system

5. Embedded

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Designed to be used in embedded computer systems.
They are designed to operate on small machines like
PDAs with less autonomy.
They are able to operate with a limited number of
resources. They are very compact and extremely efficient
by design. Windows CE and Minix 3 are some examples of
embedded operating systems.

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Process Management

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Memory Management

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Input and Output Management

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File System Management

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Intermediate

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Job Scheduling

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Security

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Network

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User Interface - GUI

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Process Management : Assignment of processor to
different tasks being performed by the computer system
Input and Output Management : Management of
communication between an information processing system
(such as a computer), and the outside world possibly a
human, or another information processing system. Inputs
are the signals or data received by the system, and
outputs are the signals or data sent from it.
Memory Management : Allocation of main memory and
other storage areas to the system programs as well as
user programs and data

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File System Management : The storage of file of various
storage devices to another. It also allows all files to be
easily changed and modified through the use of text
editors or some other files manipulation routines.
Intermediate : Facilitates easy communication between the
computer system and the computer operator.
Job Scheduling : Determines and maintains the order in
which jobs are to be executed in the computer system.
Security : Operating systems provide password protection
to keep unauthorized users out of the system.


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Network : Network is a group of two or more computer
systems linked together.
User Interface – GUI : Graphical interface of a computer
that allows users to click and drag objects with a mouse
instead of entering text at a command line. Two of the
most popular operating systems, Windows and the Mac
OS, are GUI-based.

What can you do with your OS?

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In the workplace, many people use computers to keep
records, analyze data, do research, and manage projects.
At home, you can use computers to find information, store
pictures and music, track finances, play games, and
communicate with others — and those are just a few of the
possibilities.
You can also use your computer to connect to the Internet,
a network that links computers around the world. The web,
E‑mail, Instant messaging, Pictures, music, and movies,
Gaming

Virtual Memory

Virtual Memory is where if your computer lacks the RAM
needed to run a pro gramme/operation, the Operating
system uses virtual memory to compensate for the needed
memory.Virtual Memory combines your RAM with the
temporary space on your HDD, So when there isn't
enough space on the RAM the Virtual Memory moves the
data to a temporary storage destination (paging file).

File Allocation Table

A file allocation table is a table that the operating system
uses to locate files on a disk. The name originates from
the usage of a table which centralizes the information
about which areas belong to files, are free or possibly
unusable, and where each file is stored on the disk. To limit
the size of the table, disk space is allocated to files in
contiguous groups of hardware sectors called clusters.

Buffer Work

A buffer is a region of a physical memory storage used to
temporally hold data. The purpose of most buffers is to act
as a holding area, enabling the CPU to manipulate data
before transferring it to a device. For example, word
processors use a buffer to keep track of changes to files.
Then when you save the file the word processor updates
the disk file with the contents of the buffer.

Device Driver

A device driver or software driver is a computer
programme which convert the messages from the OS into
messages that the hardware device can understand. A
device driver simplifies programming by acting as
translator between a hardware device and the applications
or operating systems that use it.

System requirements

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To be used efficiently, all computer software needs certain
hardware components or other software resources to be
present on a computer. These prerequisites.
Hardware requirements : Architecture, Processor,
Processing power, Memory, Secondary storage, Display
adapter, Peripherals.
Minimum vs Recommended.

Kernel

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A kernel connects the application software to the hardware
of a computer.
The kernel is a computer program that manages
input/output requests from software and translates them
into data processing instructions for the central processing
unit and other electronic components of a computer.
The kernel is a fundamental part of a modern computer's
operating system.

Command-line

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A command-line interface (CLI) is a means of interacting
with a computer program where the user (or client) issues
commands to the program in the form of successive lines
of text(command lines).
Command-line interfaces to computer operating systems
are less widely used by casual computer users, who favor
graphical user interfaces. Command-line interfaces are
often preferred by more advanced computer users.

Key Players – Personal Computer OS

Key Players
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Mac - Apple

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Windows - Microsoft

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Linux - The community(Us)

Windows
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Microsoft Windows is a series of graphical interface
operating systems developed, marketed, and sold by
Microsoft.
Latest version is Windows 8.1
A family of operating systems for personal computers.
Windows dominates the personal computer world, running,
by some estimates, on 90% of all personal computers.
Windows provides a graphical user interface (GUI).
Without windows you can’t operate the computer such as
system unit, monitor & keyboard.

Basic Elements Explained
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Icons are small pictures found on the desktop. These are
symbols representing programs, applications, or files.
Each icon is a shortcut to an item, file, or program inside
the computer.
Start button is the round button found on the lower part of
the desktop which you can use to open programs and
folders.
Taskbar is found at the bottom of your screen. It also
contains the start button, the middle section and
notification area.


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The NotificationArea informs you of the status of the
running program such as antivirus, printing, computer
updates, and time.
Wallpaper is the picture or design used as a background of
the desktop.
Recycle bin is temporary storage for files that have been
deleted in a file manager by the user, but not yet
permanently erased from the file system.

System requirements – Windows 8

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Processor: 1 gigahertz (GHz) or faster with support for
PAE, NX, and SSE2 (more info)

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RAM: 1 gigabyte (GB) (32-bit) or 2 GB (64-bit)

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Hard disk space: 16 GB (32-bit) or 20 GB (64-bit)

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Graphics card: Microsoft DirectX 9 graphics device with
WDDM drive

Mac
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Mac OS is a series of graphical user interface-based
operating systems developed by Apple.

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Latest version is OS X 10.9.

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Run exclusively on Mac computers.

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Unix-based graphical interface operating systems
developed.
Without mac os you can’t operate the computer such as
system unit, monitor & keyboard.


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The Dock is an array of icons which represent a variety of
programs. By default the Dock has set of programs.
At the top right of your screen there are several items. By
default you’ll find (from right to left): Spotlight, Current
User, Sound level, Date/Time, Bluetooth, Time Machine,
Wifi.
By default, with no other program running you will see the
menu items of the Finder As soon as you open another
program or switch to one the appropriate menu will appear
at this position in order for you to work with that program


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Finder : this program runs the Desktop, the contents of
your hard disk(s) and your Mac’s folder structure.
Launchpad : all your Mac’s programs are displayed.
Mission control : this will give you an overview of all you
open windows and programs. It makes it very easy to
navigate to certain windows.
App Store : just like the iTunes Store, this is a place where
you can browse and search for programs.

Linux
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Linux is a Unix-like and POSIX-compliant computer
operating system assembled under the model of free and
open source software development and distribution.
It is a leading operating system on servers and other big
iron systems such as mainframe computers and
supercomputers.
More than 95% of the world's 500 fastest supercomputers
run some variant of Linux.
Linux also runs on embedded systems such as mobile
phones, tablet computers, network routers, building
automation controls, televisions and video game consoles.

Linux
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The underlying source code may be used, modified, and
distributed - commercially or non-commercially.
Some popular mainstream Linux distributions include
Debian (and its derivatives such as Ubuntu and Linux
Mint), Fedora (and its derivatives such as the commercial
Red Hat Enterprise Linux and its open equivalent
CentOS), Mandriva/Mageia, openSUSE (and its
commercial derivative SUSE Linux Enterprise Server), and
Arch Linux.

Linux Distribution

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There are currently over six hundred Linux distributions.
Over three hundred of those are in active development,
constantly being revised and improved.
One can distinguish between commercially backed
distributions, such as Fedora (Red Hat), openSUSE
(SUSE), Ubuntu (Canonical Ltd.), and Mandriva Linux
(Mandriva), and entirely community-driven distributions,
such as Debian, Slackware, Gentoo and Arch Linux.

Linux Mint 14 Nadia with Cinnamon

Linux Types & Trends
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Commercial or non-commercial;
Designed for enterprise users, power users, or for home
users;
Supported on multiple types of hardware, or platformspecific, even to the extent of certification by the platform
vendor;
Designed for servers, desktops, or embedded devices;
General purpose or highly specialized toward specific
machine functionalities (e.g. firewalls, network routers, and
computer clusters);

Linux Types & Trends

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Targeted at specific user groups, for example through
language internationalization and localization, or through
inclusion of many music production or scientific computing
packages;
Built primarily for security, usability, portability, or
comprehensiveness.

Windows Pros
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Compatibility: Almost every application, driver or game will
work on Windows.
Technical support: Having so many users, you can always
find someone (either online or offline) who can help you
with Windows.
Huge quantity of function: When you get to know Windows
well, you'll find out that there are so many functions that
you can do almost anything quite easily.

Windows Cons

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Viruses: You may need to buy an antivirus program,
although free ones exist.
Slow: Windows, especially Vista and 7, requires a lot of
computer resources (memory, processor, disk space), and
thus, runs slower.
Price: It easily costs over a hundred dollars.

Mac Pros

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Viruses: Apple Macs get almost no viruses. This is mostly
due to Window's superior market share.
Reliability: Macs only run on Apple computers, and are
thus less prone to hardware and software crashing.
Looks: Let's face it, most of the time, Mac just looks better
than Windows.

Mac Cons

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Expensive: Mac costs even more than Windows.
Only available on Apple computers: If you already have a
computer, you cannot install MAC on it unless it's an
Apple. Otherwise, you must buy a new computer.
Compatibility: Only a few programs will run on Mac, and
almost no games.

Linux Pros
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Price: Linux is F-R-E-E. You can download it, install it, use
it, modify it. All for a 0$.
Variety: Linux is not a full operating system. It is just a
kernel. To use the kernel, additional software needs to be
bundled with Linux. Several hundreds of these bundles
(called "distributions" or simply "distros") exist. The most
popular ones include Ubuntu, Mint and Fedora. The good
thing is, with so many different flavours of Linux, there is
always one to suit your needs!
Viruses: Although being more vulnerable to viruses than
Mac (because it is open source), Linux still has very, very,
very few viruses.

Linux Pros
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Excellent community: Most of the your questions in the
forums or user Linux distributions (or simply called as
groups. You can always find a Linux a distro), especially
Ubuntu has distro for almost all of your need. excellent
community support.

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More secure and stable.

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Works on low end machines

Linux Cons
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Complicated: Although some distros are quite easy to use,
most of them will required a good deal of computer
knowledge in order to get them to work.
Compatibility: Like Mac, representing only a few percents
of the market share, Linux does not have as many
programs and games as Windows.
Vendors: You won't find a lot of vendors selling Linux
computers. Usually, you'll just end up having to buy
Windows computer, reformatting the hard drive, and
installing Linux yourself.

Linux Myths
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Linux is just for geeks.

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Linux can’t handle Excel, Word, Powerpoint.

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Linux is free, so it's bad.

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Desktops are dead, so is Linux.

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But Linux can’t handle my favorite software XYZ which is
windows-only.

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Linux can’t do gaming.

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Linux lacks support.

Bottom line

In conclusion, no operating system is really better, the
choice is up to you.

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