The document provides an overview of operating systems (OS), detailing their roles in resource management, process coordination, and user interaction, while summarizing the historical evolution from early machines to modern mobile OS. It explains key concepts like CPU scheduling, memory allocation, and protection mechanisms, along with user interfaces and the boot process. Additionally, it highlights the development of significant OS features and the shift toward networked and mobile environments.

1. S Y S T E M
Operating
This explanation covers resource management,
process/device/memory coordination, priorities,
protection, parallelism, the command interpreter,
boot process, editing, directory handling,
Directory
handling and
file handling
DOS/UNIX/
Windows-
2000
2
0
2
4

2. OPERATING SYSTEM
An Operating System is a system
software that acts as an intermediary
between the user and hardware.
Operating Systems hide the complicated
details of the hardware from the user and
provide a simple interface. They perform
functions that involve efficiently allocating
resources between user programs, file
systems, and Input-Output devices.
COMPUTER
HARDWARE
OPERATING SYSTEM
SYSTEM & APPLICATION PROGRAM
Compiler Assembler Text Editor Database
system
USER
1
USER
2
USER
3

3. OS AS RESOURCE MANAGER
Resource management includes multiplexing (sharing)
resources in two different ways: in time and space.
The OS employs CPU scheduling algorithms (e.g., Priority, Round Robin) to determine which
process gets CPU time and for how long. This ensures efficient use of the CPU and prevents
processes from starving for resources. (Example: In a multitasking environment, the OS might
allocate CPU cycles to different programs in quick succession, giving the illusion of
simultaneous execution.)
The OS assigns priorities to
processes, allowing important
tasks (e.g., system processes) to
access resources before lower-
priority ones. (Example: A real-
time video editing application
might have a higher priority than
a background music player.)
The OS protects system
resources and user data from
unauthorized access. It
employs mechanisms like
memory protection and
access control lists (ACLs) to
prevent processes from
interfering with each other.
In the bottom-up view, the
operating system provides for
an orderly and controlled
allocation of the processors,
memories, and I/O devices
among the various programs.
The OS allows multiple processes
to execute concurrently,
improving overall system
performance. Techniques like
multiprogramming and
multithreading enable this.
Operating system allows
multiple programs to be in
memory and run at the same
time.Resource management
includes multiplexing (sharing)
resources in two different ways:
in time and in space.
P
R
I
O
R
I
T
I
E
S
P
R
O
T
E
C
T
I
O
N
P
A
R
A
L
L
E
L
I
S
M

4. HISTORY OF OS
English mathematician Charles Babbage (1792–1871)
developed the first true digital computer
The history of operating systems (OS) is a fascinating
journey from basic beginnings to the complex systems
we use today. Here's a breakdown of key eras:
First Generation (1940s -
Early 1950s)
Early computers like the ENIAC were
complex machines with limited
functionality.
Users directly interacted with the
hardware using machine language, a
system of codes specific to each
machine.
Each program required manual setup
and control, making them
cumbersome and error-prone.
Second Generation
(1950s - 1960s)
The introduction of punch cards
simplified program input.
Resident monitor programs emerged,
automating the execution of multiple
programs in sequence (batch
processing).
This improved efficiency but lacked
user interactivity during execution.
Third Generation (1960s
- 1970s):
Multiprogramming: The OS allowed
multiple programs to reside in memory
simultaneously. The CPU would switch
between them rapidly, creating the
illusion of concurrent execution.
Time-Sharing: This innovation allowed
multiple users to share a single
computer system. Each user received
a designated time slot on the CPU,
enabling interactive computing.
Fourth Generation
(1970s - 1980s)
The development of the GUI
revolutionized user interaction. Users
could interact with the OS through
icons, windows, and menus instead of
complex commands.
This era saw the rise of personal
computers (PCs) and user-friendly
operating systems like:
Apple's Macintosh (1984) with its
intuitive desktop metaphor.
Microsoft Windows (1985), initially a
GUI shell for MS-DOS.
c
h
e
c
k
o
u
t
n
e
x
t
p
a
g
e
a
l
s
o
Genrations

5. HISTORY OF OS
Fifth Generation (1990s - Present): Networked
Systems and Mobile OS
The rise of networking technologies led to
distributed operating systems, enabling
resource sharing across multiple
computers.
The internet era brought the need for
secure communication and efficient
resource management.
MOBILE OPERATING
SYSTEMS
MODERN OPERATING
SYSTEMS
Mobile operating
systems emerged for
smartphones and
tablets, like:
Apple's iOS (2007) for
iPhones and iPads.
Google's Android
(2008), an open-
source platform for
various devices
Modern operating systems
continue to evolve,
incorporating features like:
Virtualization: Allows running
multiple operating systems
on a single physical machine.
Cloud computing: Enables
accessing applications and
data over the internet.
Artificial intelligence (AI):
Integration of AI for tasks like
automation and
personalization.

6. RESOURCE MANAGER AND
COORDINATOR
The Operating System (OS) acts as the central
authority, managing resources like:
b
a
s
e
d
o
n
p
r
i
o
r
i
t
i
e
s
Processor (CPU)
The OS employs CPU scheduling
algorithms (e.g., Priority, Round Robin) to
determine which process gets CPU time
and for how long. This ensures efficient
use of the CPU and prevents processes
from starving for resources. (Example: In a
multitasking environment, the OS might
allocate CPU cycles to different programs
in quick succession, giving the illusion of
simultaneous execution.)
Memory
The OS allocates memory to running
processes. It uses techniques like paging
and segmentation to organize memory
efficiently. It also handles virtual memory,
allowing processes to use more memory
than physically available. (Example: When
you open a new program, the OS allocates
a portion of memory for its instructions
and data.)
Devises
The OS manages access to devices like
printers and disks. It handles device
drivers that translate generic commands
into device-specific instructions. It also
prevents conflicts when multiple
programs try to access the same device.
(Example: A print queue manages print
jobs from various applications, ensuring
each job prints sequentially.)
The OS assigns priorities to processes, allowing important tasks (e.g.,
system processes) to access resources before lower-priority
ones.Example: A real-time video editing application might have a higher
priority than a background music player.
The OS protects system resources and user data from unauthorized
access. It employs mechanisms like memory protection and access control
lists (ACLs) to prevent processes from interfering with each other.
(Example: The OS prevents one program from modifying another
program's memory space.)
The OS allows multiple processes to execute concurrently, improving
overall system performance. Techniques like multiprogramming and
multithreading enable this. (Example: While you download a file, the OS
might also be running a virus scan in the background.)

7. COMMAND INTERPRETER
(SHELL)
A command interpreter, also commonly referred to as a
shell, acts as a translator between you and the
operating system
The shell accepts commands from the user in the
form of text lines.
These commands can be:
Internal shell commands: Built-in functions of the
shell itself, like cd (change directory) or ls (list
directory contents).
External commands: Separate programs
accessible through the shell, like cp (copy) or mv
(move) for file manipulation.
The shell interprets the command and translates it
into instructions the operating system understands.
It then executes the command or program and
displays the results on the screen
Command Proceesing

8. BOOT PROCESS
The boot process is the sequence of events
that occur when a computer starts. It involves
loading the OS into memory and preparing
the system for user interaction. Here's a
simplified breakdown:
Bootloader
Hardware diagnostics ensure
basic functionality.
Power On Self Test
(POST)
Locates and loads the
kernel, the core of the OS
Kernel Initialization
Initializes memory
management, device drivers,
and other core services.
User Interface
Loads the shell or graphical
user interface (GUI) for user
interaction.
Note: The specific boot process may vary
depending on the OS.

9. DOS
Editing, Directory
Handling, and File
Handling
Editing
External text editors
like Edit are used for
creating and
modifying text files.
Directory Handling
The cd command is
used to change
directories, and dir
displays directory
listings.
File Handling
DOS uses commands
like copy, move, and
del to manage files

10. UNIX
Editing, Directory
Handling, and File
Handling
Built-in command-line editors like
vi and emacs are commonly used
Commands like cd, pwd, ls, and mkdir
are used for navigation, listing, and
creating directories.
Powerful utilities like cp, mv, rm,
and cat manage file copying,
moving, deletion, and viewing.
EDITING
DIRECTORY HANDLING
FILE HANDLING
c
h
e
c
k
o
u
t
n
e
x
t
p
a
g
e
a
l
s
o

11. WINDOWS 2000
Editing, Directory
Handling, and File
Handling
Notepad is a basic text editor included with
the OS. Third-party options offer advanced
features
EDITING
The OS provides a user-friendly interface for
copying, moving, deleting, and viewing files
through drag-and-drop actions and context
menus
EDITING
The graphical user interface allows for easy
navigation and management of directories
using a hierarchical file system.
DIRECTORY HANDLING