The document discusses the key components and functions of an operating system: 1. It manages computer hardware resources and allows for the execution of user programs and applications. 2. It provides services like process management, memory management, file management, I/O management, and protection to programs and users. 3. Operating systems provide an interface between the user and computer system through functions like command interpretation.

2. 1. Hardware: which provides basic computing
resources (CPU, memory, I/O
devices).
2. Operating system: which manages the use of
the hardware among the various
application programs for the various users
and provides the user a relatively
simple machine to use.

3. 3. Applications programs: that define the ways
in which system resources are used
to solve the computing problems of the users
(compilers, database systems, video
games, business programs).
4. Users: which include people, machines,
other computers.

5.  A program that acts as an intermediary
between a user of a computer and the
computer hardware.
 Operating system goals:
◦ Execute user programs and make solving user problems easier.
◦ Make the computer system convenient to use.
 Use the computer hardware in an efficient
manner.

6. 1. Single User Operating System
2. Multi-User Operating System

7.  You will find this kind of operating system on
a personal computer.
 The operating system is designed mainly with
a single user in mind, but it can deal with
many applications running at the same time.
For example, you might be writing an essay,
while searching the internet, downloading a
video file and also listening to a piece of
music.

8.  Example operating systems are:
 Windows
 Linux
 Mac OS

9.  A term describing an operating system or
application program that can be used by
several people concurrently; opposite of
single-user. Unix is an example of a multi-
user operating system, whereas most (but not
all) versions of Microsoft Windows are
intended to support only one user at a time.

10.  Starts the computer operations.
 Schedule jobs.
 Passes the control from one program to the
next.
 Jobs queuing.
 Control program execution.
 Manage data and file storage.
 Assign different tasks to the CPU.
 Monitors fault or errors in a program and
displays suitable error message which helps
the user to find the source of fault.

11. An operating system provides the
environment within which programs are
executed. It provides services to programs
and users of those programs which vary from
operating system to operating system. Some
of the common ones are:
 Program execution
 i/o operation
 File system management
 Communication

12.  Error Detection
 Resource Allocation
 Protection
 Program Execution:
The system must be able to load a program
into memory and to run that program. The
program must be able to end its execution.

13.  I/O Operations:
A running program may require I/O, which
may involve an I/O device. For efficiency and
protection, user can’t control I/O devices
directly. The operating system provides a
means to do I/O.
 File System Management:
Programs need to read, write files. Also they
should be able to create and delete files by
name.

14.  Communication:
There are many circumstances in which one
process needs to exchange information with
another process. Such communication may occur
between processes. that are executing on the
same computer or between processes that are
executing on different computer systems tied
together by a computer network.
 Error Detection:
The operating system constantly needs to be
aware of possible errors. Error may occur in the
CPU and memory hardware (such as a memory
error)

15.  in I/O devices (such as a connection failure
on network or lack of paper in the printer),
and in the user program (such as an
arithmetic overflow)

16.  Resource Allocation:
When there are multiple users logged on the
system or multiple jobs running at the same
time, resources must be allocated to each of
them. Many different types of resources are
managed by the operating system, some
(such as CPU cycles, main memory and file
Storage)

17.  Protection:
The owner of information stored in a multi-
user computer system may want to control
use of that information. When several
processes execute concurrently it should not
be possible for one process to interfere with
the other or with the operating system itself.
Protection involves ensuring that access to
system resources is controlled.

18. • An operating system has many components
that manage all the resources in a computer
system, insuring proper execution of
programs.
 We briefly describe these components in this
section.
 Process management
 Main memory management
 Secondary memory management

19.  I/O System management
 File management
 Networking
 Protection system
 Command interpreter system

20. A process can be thought of as a program in
execution. It needs certain resources, including
CPU time, memory, files and I/O devices to
accomplish its tasks.
 The operating system is responsible for:
1. Creating and terminating both user and system
processes
2. Suspending and resuming processes
3.Providing mechanisms for processes
communication.
4. Providing mechanisms for deadlock handling

21. Main-memory provides storage that can be access
directly by the CPU. That is to say for a program to
be executed, it must be in the main memory.
The major activities of an operating system in
regard to memory-management are:
 Keep track of which part of memory are currently
being used and by whom.
 Decide which process are loaded into memory
when memory space becomes available.
 Allocate and deallocate memory space as needed.

22. Generally speaking, systems have several levels of
storage, including
1.primary storage
2.secondary storage
3.cache storage
Instructions and data must be placed in primary
storage or cache to be referenced by a running
program. Because main memory is too small to
accommodate all data and programs, and its data
are lost when power is lost, the computer system
must provide secondary storage to back up main
memory.

23. The two major activities of an operating system
in regard to secondary storage management
are:
 Managing the free space available on the
secondary-storage device.
 Allocation of storage space when new files
have to be written.

24. A file is a collected of related information
defined by its creator. Computer can store files
on the disk (secondary storage), which provide
long term storage.
The three main major activities of an operating
system in regard to file management are
 The creation and deletion of files.
 The mapping of files on to secondary storage.
 The back up of files on stable storage media.

25. The processors communicate with one another
through communication lines called network.
The communication-network design must
consider routing and connection strategies,
and the problems of contention and security.

26.  If a computer systems has multiple users and
allows the concurrent execution of multiple
processes, then the various processes must
be protected from one another's activities.
Protection refers to mechanism for
controlling the access of programs,
processes, or users to the resources defined
by a computer systems.

27.  A command interpreter is an interface of the
operating system with the user. The user
gives commands which are executed by
operating system The main function of a
command interpreter is to get and execute
the next user specified command.