2. Introduction
Computer software gives instructions that make
computer hardware work. In other words, software is
a collection of computer programs and related data
that provide the instructions for telling a computer
what to do and how to do it.
The four main types of software are operating
systems, application programs, utility programs, and
programming languages.
4. Operating Systems
An operating system is a piece of software
that controls how hardware resources such as
memory, the central processing unit (CPU),
disk space, and other devices are used. All
other kinds of software (application, utility,
and programming) need the operating system
because of hardware resources.
5. Operating Systems
An operating system has two parts, a
kernel, and a shell. The kernel is the
core of an operating system. It
manages memory, files, and other
devices; maintains the time and date;
starts applications; and manages
system resources.
The shell provides direct
communication interface between the
user and the kernel.
6. Operating Systems
There are many different types of operating
system. They are classified systems according to
the type of user interface, how many users they
support (single-user or multi-user), how they
perform tasks (single task or multitask), and how
they work with other computers (single computer
or network).
9. Single or Multi-User
A single-user operating system can be used
only by a single user. A multiuser operating
system can be used by more than one user.
In some ways, a computer that several
people share is like a multi-user system.
However, a real multi-user system means a
machine (and operating system) that
several people can access at the same time,
through communication facilities or
network terminals. Server computers are
multi-user systems whereas, PC’s or
workstations are single-user systems.
10. Stand Alone or Network
A network operating system is an operating system
specifically designed to support computer networks. A
computer network is a set of computers that can communicate
with each other and share resources. A network operating
system uses a special machine called a server to provide
networking support for multiple simultaneous users as well as
administrative, security, and management functions. Unlike a
single-user operating system, a network operating system
must respond to requests from many computers, managing
network access and communications, resource use and
sharing, data protection, and error control.
17. Application Programs
An application program is a
program designed to help with a
specific task, such as word
processing, accounting, counting
the items in a shop or
warehouse, or maintaining a
database. Application software
makes a computer work to suit
your needs.
