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1. COMPUTER SOFTWARE
Computer Software, or simply software, is a part of a
computer system that Consists of data or computer
instructions, in contrast to the physical hardware from
which the system is built. In computer science and
software engineering, computer software is all
information processed by computer systems, programs
and data. Computer software includes computer
programs, libraries and related non- executable data, such
as online documentation or digital media. Computer
hardware and software require each other and neither can
be realistically used on its own.

2. Types:-Based on the goal, computer software can be
divided into:
•Application software
which is software that uses the computer system to
perform special functions or provide entertainment
functions beyond the basic operation of the computer
itself.
•System software
which is software that directly operates the computer
hardware, to provide basic functionality needed by
users and other software, and to provide a platform for
running application software. System software includes

3. •Operating systems:-which are essential collections of
software that manage resources and provides common
services for other software that runs "on top" of them.
•Device drivers
which operate or control a particular type of device that
is attached to a computer. Each device needs at least
one corresponding device driver; because a computer
typically has at minimum at least one input device and
at least one output device, a computer typically needs
more than one device driver.
• Utilities
which are computer programs designed to assist users in
the maintenance and care of their computers.

4. Operating system:-An operating system (OS) is system
software that manages computer hardware and software
resources and provides common services for computer
programs.
Time-sharing operating systems schedule tasks for
efficient use of the system and may also include
accounting software for cost allocation of processor
time, mass storage, printing, and other resources.
The operating system acts as an intermediary between
programs and the computer hardware, although the
application code is usually executed directly by the
hardware and frequently makes system calls to an OS
function or is interrupted by it.

5. Types of operating systems
1. Single- and multi- tasking: - A single-tasking system
can only run one program at a time, while a multi-
tasking operating system allows more than one
program to be running in concurrency. This is achieved
by time-sharing, where the available processor time is
divided between multiple processes. These processes
are each interrupted repeatedly in time slices by a task-
scheduling subsystem of the operating system. Multi-
tasking may be characterized in preemptive and co-
operative types. In preemptive multitasking, the
operating system slices the CPU time and dedicates a
slot to each of the programs.

6. 2. Single- and multi-user:- Single-user operating systems
have no facilities to distinguish users, but may allow
multiple programs to run in tandem. A multi-user operating
system extends the basic concept of multi-tasking with
facilities that identify processes and resources, such as disk
space, belonging to multiple users, and the system permits
multiple users to interact with the system at the same time.
Time-sharing operating systems schedule tasks for efficient
use of the system and may also include accounting software
for cost allocation of processor time, mass storage, printing,
and other resources to multiple users.

7. 3.Distributed:- A distributed operating system manages a
group of distinct 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.
4.Template:- In an OS, distributed and cloud computing
context, templating refers to creating a single virtual
machine image as a guest operating system, then saving it
as a tool for multiple running virtual machines. The
technique is used both in virtualization and cloud
computing management, and is common in large server
warehouses.

8. 5. Embedded:- Embedded operating systems are 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.
6. Real-time:- A real-time operating system is an
operating system that guarantees to process events or data
by a specific moment in time. A real-time operating system
may be single- or multi-tasking, but when multitasking, it
uses specialized scheduling algorithms so that a
deterministic nature of behavior is achieved.

9. 7. Library:- A library operating system is one in which
the services that a typical operating system provides,
such as networking, are provided in the form of libraries
and composed with the application and configuration
code to construct a uni kernel: a specialized, single
address space, machine image that can be deployed to
cloud or embedded environments.

10. Booting Your Computer
•Introduction
•Booting is a startup sequence that starts the operating
system of a computer when it is turned on. A boot
sequence is the initial set of operations that the
computer performs when it is switched on. Every
computer has a boot sequence. The average computer
doesn’t understand the boot sequence but is important to
know for customizing and troubleshooting your
computer.

11. Boot Devices
•The boot device is the device from which the operating
system is loaded. A modern PC BIOS (Basic Input/Output
System) supports booting from various devices.
These include the local hard disk drive, optical drive,
floppy drive, a network interface card, and a USB
device. Typically, the BIOS will allow the user to
configure a boot order. If the boot order is set to:
•CD Drive
•Hard Disk Drive

12. Directory
A directory is a location for storing files on your
computer. Directories are found in a hierarchical file
system, such as Linux, MS-DOS, OS/2, and Unix.
In the picture to the right is an example of the tree
command output that shows all the local and
subdirectories. When looking at this overview, the C:
drive is considered the current directory and root
directory because there is nothing beneath it and you
can't go back any further. If you are using an operating
system with multiple user accounts the directory may
also be referred to as a home directory.

13. Computer file
A computer file is a computer resource for
recording data discretely in a computer storage
device. Just as words can be written to paper, so can
information be written to a computer file.
Volume
In computer data storage, a volume or logical drive is a
single accessible storage area with a single file system,
typically (though not necessarily) resident on a single
partition of a hard disk.

14. Two Basic Types of Computer Language
Low-Level Languages: A language that corresponds
directly to a specific machine
High-Level Languages: Any language that is independent
of the machine There are also other types of languages,
which include
System languages: These are designed for low-level tasks,
like memory and process management.
Scripting languages: These tend to be high-level and very
powerful.
Domain-specific languages: These are only used in very
specific contexts.

15. Visual languages: Languages that are not text-based.
Esoteric languages: Languages that are jokes or are not
intended for serious use.
Low-Level Languages
Low-level computer languages are either machine codes
or are very close them. A computer cannot understand
instructions given to it in high-level languages or in
English. It can only understand and execute instructions
given in the form of machine language i.e. binary. There
are two types of low-level languages:
• Machine Language
• Assembly Language

16. Machine Language: a language that is directly interpreted
into the hardware.
Assembly Language: a slightly more user-friendly
language that directly corresponds to machine language.
Machine Language
Machine language is the lowest and most elementary
level of programming language and was the first type of
programming language to be developed. Machine
language is basically the only language that a computer
can understand and it is usually written in hex.

17. Assembly Language
Assembly language was developed to overcome some of
the many inconveniences of machine language. This is
another low-level but very important language in which
operation codes and operands are given in the form of
alphanumeric symbols instead of 0’s and l’s.

18. High-Level Languages
High-level computer languages use formats that are similar to
English. The purpose of developing high-level languages was to
enable people to write programs easily, in their own native language
environment (English).
Advantages:-
1. High-level languages are user- friendly.
2. They are similar to English and use English vocabulary and
well-known symbols.
3. They are easier to learn.
4. They are problem-oriented rather than 'machine'-based.
5. They are easier to maintain.

19. Disadvantages:-
1. A high-level language has to be translated into the machine
language by a translator, which takes up time.
2. The object code generated by a translator might be
inefficient compared to an equivalent assembly language
program.