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OS Basics
OS Basics
Outline
1
2
3
4
OS Basics
Key Concepts
A Bit of History
Activity - File System
Outline
1
2
3
4
OS Basics
Key Concepts
A Bit of History
Activity - File System
1
OS Basics
• We said you can view a
computer as a machine
made of layers
• The OS sits in a special
place in these layers
• It’s right between all the
hardware and the apps
we use for work & play
1
OS Basics
Operating
System
So a good OS
makes everything
look simple to the
user who doesn’t
worry what’s
happening behind
the scenes
The OS sits
between
all the hardware &
applications,
managing the
resources for the
whole system.
1
OS Basics
1AOSThe
BasicsBigger
Picture
• Software means all the programs that
contain the instructions to tell the
computer what to do.
• There are two main types of software:
systems software and applications,
which we’ll cover later.
• We’re now focusing on the operating
system because it’s the prime
example of systems software.
1B OSWhat
Basics
Is An OS ?
The operating system controls the
operation of the computer.
• It manages all the hardware and
software or programs.
• And it provides a link between user
and computer.
Basically, a computer simply wouldn’t
work without the operating system !
1COSTwo
BasicsTypes
of OS
Server OS
Client OS
Controls the server
behind the scenes
in a network.
Controls a
computer for
one user.
How
The
OS
Takes
Over
D
1 OS
Basics
BIOS
Storage
OS
Memory
CPU
3
1
2
1 Computer boots using the BIOS ROM
2 The OS is loaded from storage into RAM
3 The CPU starts the fetch-execute cycle
1E OSFunctions
Basics
of an OS
The OS handles several key functions in
a computer, such as:
1) User interface
2) Multi-Tasking
3) Memory Management
4) File Management
5) Peripheral Management
6) Security
7) Utilities
More follows on the ‘Extra’ pages.
1E OSFunctions
Basics
of an OS
The OS uses programs called utilities to
handle housekeeping tasks, such as:
• Anti-virus: Utility to protect from
malicious programs called viruses
• System Clean-up: Deletes old system
files to clear storage space
• Disk De-frag: Re-arranges files on a
hard drive to improve access times
• Software Updates: Automates
downloads of software updates
1
OS Basics
1i
User
OS
BasicsInterface
Graphical
Command Line
A Graphical User
Interface (GUI) uses
windows, icons,
menus & the pointer
(WIMP).
A Command Line
Interface (CLI) uses a
prompt where users
type commands,
such as with Linux.
Multi-Tasking
1ii OS
Basics
The OS makes it possible to run several programs at once.
BIOS
Storage
Software Memory
CPU
Memory
1iiiOS
Basics
Management
The OS also divides up the RAM to share it
between different applications.
BIOS
Storage
Software Memory
CPU
File
Management
1ivOS
Basics
The OS organises all the files you install or save on
storage, such as the hard drive
Storage
Software
v Peripheral Management
The OS manages connections with i/o peripherals
using special programs called device drivers.
Device
Drivers
iv File Management
The OS provides security by handling logon
accounts and passwords, as well as access rights.
1
OS Basics
1
OS Basics
• Going forwards, you will
need to keep this general
background in mind to
understand what an OS is
doing overall
• But we’ll actually focus on
only a few key concepts
for an OS…
Outline
1
2
3
4
OS Recap
Key Concepts
A Bit of History
Activity - File System
2
Key Concepts
You’ll now be
making some
quick notes in
this booklet…
2
Key Concepts
One key concept is the User interface – and
remember there are two types…
Graphical User Interface
This is the WIMP interface that
we’re all used to
Command Line Interface
This is the text-based interface
that’ll also soon become familiar!
2
Key Concepts
Another key concept is the File System, which is
how the OS manages what needs storing…
Folders
Is how the OS organises what’s
stored in a computer & other devices
Files
Is the actual data in various file types,
such as documents and media
2
Key Concepts
And a final key concept is User Management,
which is controlling who can access resources
System Administrators
Means the ‘admins’ who have the
most rights & privileges to run things
Ordinary ‘Users’
Means normal people who have less
‘rights’ when using a computer
2
Key Concepts
• So our first goal for these prep lessons is to use
the Windows GUI to do admin on files & users
• Our second goal is to explore the command line
in Windows for doing those admin tasks
• And our final goal is to introduce you to using
Linux and its command line to do admin tasks
• That will be more tricky – but also more fun!
Today’s Lesson
1
2
3
4
OS Recap
Key Concepts
A Bit of History
Activity - File System
3
A Bit Of History
• We’ll now pause for a
quick history lesson!
• That’s because it will
help us focus on key
concepts such as the
user interface and
file systems and
why they work the
way they do…
1940
1950
Thompson & Ritchie
1960
Unix
MS-DOS
71
81
1970
Bill Gates
Mac OS Win 1.0
84
1980
85
Linux
199091
Steve Jobs
Android 1
2012
2000
Linus Torvalds
2010
3
A Bit Of History
• So each OS has influenced the others
• Unix is like an ancestor to lots of
operating systems, such as Linux
• And Windows started life as MS-DOS &
that remained its core for years
• Now Linux is used as the core of
Android, the mobile OS from Google
• So it’s worth noting that OS are also
built in layers from a core…
3
A Bit of History
Programs that we
use for work & play
Applications
OS
Libraries
& Tools
Kernel
Libraries & Tools
Set of programs that
extend the kernel with
features such as the
user interface.
Kernel
Hardware
Is the core of the
operating system that
interfaces with the
hardware
3
A Bit of History
Applications
Libraries
Windows
& Tools
MS-DOS
MS-DOS
Hardware
Was the original core
of Windows and is the
forerunner of today’s
Command Line
3
A Bit Of History
• So the origins of the command line
interface lie with the original operating
systems, such as Unix and MS-DOS
• That means that all file handling, for
example, was done using text
• So no nice icons for folders and files!
• That has had a big influence on File
Systems for all operating systems
• We’ll explore that now with an activity
Today’s Lesson
1
2
3
4
A Bit of History
OS Recap
Key Concepts
Activity - File System
4
Activity - File System
• The File System means the methods
used by an OS to name & store files so
they can be opened quickly and easily
• The File System lets to access files on
storage devices, such as the hard drive
• It also allow us to access external
storage devices, such as USB sticks
• And is even includes network ‘drives’,
such as ‘Student Resources’
4
Activity - File System
• Ordinary computer users understand
this by saying they put files into folders
• But we need to start learning how
computer scientists look at file systems
• And that includes some new terms for
familiar words…
4
Activity - File System
• For a start, ever since the
days of Unix, computer scientists
say that files are stored in
directories, not folders
• And directories are organised in a
hierarchical structure called a tree
• Here is an example of the start of
what’s called a tree directory
structure…
Hard Drive (C:)
My Documents
Home
Work
Yes – this is a geeky version of a tree!
Computer scientists actually love trees
Not to hug…but to show data structures…
Root
Hard Drive (C:)
My Documents
Branch
Home
Leaf
Work
Root
Branch
Leaf
These are classic terms in computer science
There are lots of algorithms for using trees
And many ways to structure data in ‘trees’
Hard Drive (C:)
My Documents
Home
Work
So a ‘tree’ is the classic way to handle files
Behind the scenes, the OS uses a tree structure
Not with cute ‘GUI’ icons but using paths…
Root
Hard Drive (C:)
C:\
It all starts with the ‘root’ directory
Root is always given a letter as a label
‘C’ is traditional for a hard drive on Windows
Hard Drive (C:)
My Documents
C:\ My Documents
Now we move to the next directory
And add the next part of the path…
It’s starting to look a bit like a web address…
Hard Drive (C:)
My Documents
Home
C:\ My Documents \Home
Here’s the next directory & updated path…
Hard Drive (C:)
My Documents
Home
Work
C:\ My Documents\Work
And the final directory, with another slash…
4
Activity - File System
So here’s a completed file path…
C:\ My Documents\Work
Root
Directory
Back slash
Is the hard
drive for C:
Is a folder
Opposite to
websites!
4
Activity - File System
• Let’s now expand that idea to
a typical set of folders
(directories) and files that
someone might store.
• Imagine these are the files
for someone called Sally
• She’s not like a typical teen
• Her stuff is organised…!
• So we can practice with paths
My Documents
Meeting.ppt
Home
Game.swf
Photos
Song.mp3
Beach.jpg Graphic.gif
Work
Training
Video1.mp4
Shopping.txt
Budget.xls
Page.html
Club
Members
Poster.pdf
Database.mdb
Report.doc