This document defines software and discusses its classes, basic principles, evolution, and laws. It states that software consists of instructions that tell hardware how to perform tasks. There are three main classes: system software runs hardware/systems, application software allows users to perform tasks, and programming software aids development. Software evolves through maintenance/updates as requirements and technology change to continuously adapt. Eight laws govern software evolution, including that software must continue adapting to real-world changes or lose usefulness over time.

1. IT 226
APPLICATIONS DEVELOPMENT
AND EMERGING TECHNOLOGIES

2. What is a
Software?

3. Lesson Objectives:
At the end of this lesson, you will be able to:
• Define what is a software and its classes
• Identify the basic principles of a software
• Identify the software evolution and laws

4. Software
• Software is capable of performing many
tasks, as opposed to hardware which
can only perform mechanical tasks that
they are designed for. Software provides
the means for accomplishing many different
tasks with the same basic hardware

6. Classes of
Software

7. System Software
• Helps run the computer hardware and computer system itself.
System software includes operating systems, device drivers,
diagnostic tools and more. System software is almost always
pre-installed on your computer.

12. Application software
• Allows users to accomplish one or more
tasks. It includes word processing, web
browsing and almost any other task for
which you might install software. (Some
application software is pre- installed on
most computer systems.)

14. Programming software
• A set of tools to aid developers in writing
programs. The various tools available are
compilers, linkers, debuggers, interpreters
and text editors.

16. Basic Principles
1. Software, commonly known as programs
or apps, consists of all the instructions that
tell the hardware how to perform a task.
2. These instructions come from a software
developer in the form that will be accepted
by the platform (operating system + CPU)
that they are based on.

17. Basic Principles
For example, a program that is designed for
the Windows operating system will only
work for that specific operating system.
Compatibility of software will vary as the
design of the software and the operating
system differ. Software that is designed for
Windows XP may experience a
compatibility issue when running under
Windows 2000 or NT.

19. Basic Principles
3. Software, in its most general sense, is a set
of instructions or programs instructing a
computer to do specific tasks. Software is a
generic term used to describe computer
programs. Scripts, applications, programs
and a set of instructions are all terms often
used to describe software.

20. Software
Evolution

21. Software Evolution
The process of developing a software
product using software engineering principles
and methods is referred to as software
evolution. This includes the initial development
of software and its maintenance and updates, till
desired software product is developed, which
satisfies the expected requirements.

22. Software Evolution
Evolution starts from the requirement
gathering process. After which developers
create a prototype of the intended software and
show it to the users to get their feedback at the
early stage of software product development.
The users suggest changes, on which several
consecutive updates and maintenance keep on
changing too.

23. Software Evolution
This process changes to the original
software, till the desired software is accomplished.
Even after the user has desired software in hand,
the advancing technology and the changing
requirements force the software product to
change accordingly. Re-creating software from
scratch and to go one-on-one with requirement is
not feasible. The only feasible and economical
solution is to update the existing software so that
it matches the latest requirements.

24. Change
Request
Impact
Analysis
Release
Planning
System
Update
System
Release

25. Laws in Software
Evolution

26. Eight Laws for
Software Evolution

27. Eight laws for software evolution
1. Continuing Change
A software system must continue to adapt to
the real world changes, else it becomes
progressively less useful.

28. Eight laws for software evolution
2. Increasing Complexity
A software system evolves, its complexity
tends to increase unless work is done to
maintain or reduce it.

29. Eight laws for software evolution
3. Conservation of familiarity
The familiarity with the software or the
knowledge about how it was developed, why
was it developed in that particular manner
etc. must be retained at any cost, to
implement the changes in the system.

30. Eight laws for software evolution
4. Continuing Growth
In order for a system intended to resolve
some business problem, its size of
implementing the changes grows
according to the lifestyle changes of the
business.

31. Eight laws for software evolution
5. Reducing Quality
A software system declines in quality
unless rigorously maintained and
adapted to a changing operational
environment.

32. Eight laws for software evolution
6. Feedback Systems
The software systems constitute multi-loop,
multi-level feedback systems and must be
treated as such to be successfully modified or
improved.

33. Eight laws for software evolution
7. Self-regulation
A system evolution processes are self-
regulating with the distribution of
product and process measures close to
normal.

34. Eight laws for software evolution
8. Organization Stability
The average effective global activity rate
in an evolving a system is invariant over
the lifetime of the product.