Software vs Hardware

What is Software

• Software consists of programs, data, and descriptive information.
• Instructions or computer programs provide desired features, function, and performance when executed are software
• Data structures enable programs to adequately manipulate information
• Documentation is a component of software and describes the operation/use of the programs.
• Software is engineered/developed, not manufactured in the classic sense.
• Software does not "wear out".
• Most software continues to be custom-built, despite the industry's move toward component-based construction.

Hardware

• Hardware has relatively high failure rates early in its life.
• Hardware defects are corrected
• Hardware's failure rate drops to a steady-state level for some time.
• As time passes, the hardware failure rate rises again as components suffer from cumulative effects/abuse which cause it to wear out.

Software: The Changing Nature

• Software is not susceptible to environmental maladies that cause hardware to wear out.
• Theoretically, the failure rate curve for software should take the form of an idealized curve.
• Undiscovered defects cause high failure rates early in a program's life; these defects are corrected, and the curve flattens.
• Software deteriorates as it undergoes change during its life

Software Applications

• System software services other programs, including determinate items like compilers, editors, and file management utilities.
• Indeterminate system software includes operating systems and network software because of unpredictable inputs.
• Application software includes stand-alone programs that solve a specific business need.
• Engineering/scientific software includes a broad array of number-crunching programs used in astronomy, volcanology, automotive stress analysis, orbital dynamics, computer-aided design, molecular biology, genetic analysis, and meteorology
• Embedded software resides within a product/system and is used to implement/control features and functions for the end user and for the system itself.
• Product-line software provides a specific capability for use by many different customers, like inventory control products.
• WebApps (Web applications) are browser-based apps, including software that resides devices.
• AI software uses nonnumerical algorithms to solve complex problems that are not amenable to computation or straightforward analysis, like Robotics, expert systems, pattern recognition, artificial neural networks, theorem proving, and game playing

New Software Categories

• Open-world computing is pervasive, distributed computing.
• Ubiquitous computing involves wireless networks.
• Netsourcing & Cloud Computing relates to the Web as a computing engine.
• Open source "free" code is open to the computing community.
• New Software Categories also now includes data mining, grid computing, cognitive machines and software for nanotechnologies.

Legacy Software

• Legacy software consists of very old programs, which support core business functions, and are indispensable to the business.
• Legacy software characteristics include longevity and business criticality.
• Legacy software has been the focus of continuous attention and concern since the 1960s.

Software Engineering: Definition of Discipline

• The IEEE defines software engineering as the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software; that is, the application of engineering to software.
• A "systematic, disciplined and quantifiable” approach applied by one software team may be burdensome to another.
• Discipline is needed with adaptability and agility in software engineering.

Software Engineering: A Layered Technology

• Software engineering is composed of tools, methods, and a process model which results in a "quality" focus.

Software Engineering Process

• The software engineering process layer is the foundation of software engineering.
• Process is the glue that holds the technology layers together and enables rational and timely development of computer software.
• Process defines a framework for effective delivery of software engineering technology and forms the basis for management control of software projects.
• The process layer establishes the context in which technical methods are applied, work products are produced, milestones are established, quality is ensured, and change is properly managed.

Software Engineering Methods

• Methods provide the technical how-to's for building software.
• Methods encompass an array of tasks that include communication, requirements analysis, design modeling, program construction, testing, and support.
• Methods rely on basic principles that govern each area of the technology and include modeling activities/descriptive techniques.

Software Engineering Tools

• Tools provide automated or semi-automated support for the process and the methods.
• Computer-aided software engineering tools can be integrated so that information created by one tool can be used by another.

Software Process

• A process is a collection of activities, actions, and tasks that are performed when some work product is to be created.
• An activity strives to achieve a broad objective, such as communication and is applied regardless of the application domain, size of the project, or complexity of the effort.
• An action encompasses a set of tasks that produce a major work product, such as architectural design.
• A task focuses on a well-defined objective that produces a tangible outcome.

Process Framework

• The process framework establishes the foundation for a complete software engineering process by identifying a small number of framework activities that are applicable to projects, regardless of their size or complexity.
• The process framework encompasses a set of umbrella activities that are applicable across the entire software process.

Framework Activities: General Setting

• Framework activities include communication, planning, modeling, construction, and deployment.
• Modeling includes the analysis of requirements and design
• Construction includes code generation and testing

Communication

• Before any technical work can commence, communication and collaboration with the customer (and other stakeholders) is critical.
• The intent is to understand stakeholders' objectives and to gather requirements that help define software features and functions.

Planning

• Any complicated journey can be simplified if a map exists.
• A software project is a complicated journey, and the planning activity creates a "map" that helps guide the team as it makes the journey.
• This map, which is also called a software project plan, defines the software engineering work by describing the technical tasks to be conducted, the risks that are likely, the resources that will be required, the work products to be produced, and a work schedule.

Modeling

• Whether you're a landscaper, a bridge builder, an aeronautical engineer, a carpenter, or an architect, you work with models every day.
• You create a "sketch" of the thing so that you'll understand the big picture
• What it will look like architecturally, how the constituent parts fit together, and many other characteristics.
• If required, you refine the sketch into greater and greater detail in an effort to better understand the problem and how you're going to solve it.
• A software engineer does the same thing by creating models to better understand software requirements and the design that will achieve those requirements.

Construction

• Construction is code generation (either manual or automated) and the testing that is required to uncover errors in the code.

Deployment

• The software (as a complete entity or as a partially completed increment) is delivered to the customer who evaluates the delivered product and provides feedback based on the evaluation.

Process Framework: Iteration

• Communication, planning, modeling, construction, and deployment are applied repeatedly through a number of project iterations.
• Each project iteration produces a software increment that provides stakeholders with a subset of overall software features/functionality.
• For each increment, the software becomes more and more complete

Umbrella Activities

• Software project tracking and control.
• Risk management.
• Software quality assurance.
• Technical reviews.
• Measurement.
• Software configuration management.
• Reusability management.
• Work product preparation and production.

Process Adaptation

• Software engineering process should be agile and adaptable (to the problem, to the project, to the team, and to the organizational culture).
• A process adopted for one project might be significantly different than a process adopted for another project.
• Differences include the overall flow of activities, actions, and tasks and the interdependencies among them.
• The difference resides in the degree to which actions and tasks are defined within each framework, also the degree to which work products are identified and required
• Differences depends upon the manner in which quality assurance and project tracking/control activities are applied, and the overall degree of detail and rigor with which the process is described.
• Difference depends on the degree to which the customer and stakeholders are involved with the project
• Difference depends on level of autonomy given to the software team, and the degree to which team organization and roles are prescribed

Software Engineering Practice

• There are generic framework activities—communication, planning, modeling, construction, and deployment—and umbrella activities establish a skeleton architecture for software engineering work.

The Essence of Practice

• Polya suggests the following:
  • Understand the problem through communication and analysis.
  • Plan a solution through modeling and software design.
  • Carry out the plan through code generation.
  • Examine the result for accuracy through testing and quality assurance.

Hooker's General Principles

• Include; The Reason It All Exists, KISS (Keep It Simple, Stupid!), Maintain the Vision, What You Produce, Others Will Consume, Be Open to the Future, Plan Ahead for Reuse, and Think!.

How It All Starts

• Every software project is precipitated by some business need
  • The need to correct a defect in an existing application
  • The need to adapt a 'legacy system' to a changing business environment
  • The need to extend the functions and features of an existing application
  • The need to create a new product, service, or system

Chapter 1: Summary

• Software is the key element in the evolution of computer-based systems/products and one of the most important technologies.
• Over the past 50 years, software has evolved from a specialized problem-solving/information analysis tool to an industry in itself.
• There remains trouble developing high-quality software on time and within budget
• Software (programs, data, descriptive information) addresses a wide array of technology and application areas.
• Legacy software continues to present special challenges to those who must maintain it, as the nature of software is changing
• Web-based systems/applications have evolved and mobile applications present new challenges as apps migrate to several platforms.
• Cloud computing transforms how software is delivered and the environment in which it exists.
• Software engineering encompasses processes, methods, and tools that enable complex computer-based systems to be built in a timely manner with quality.
• The software process incorporates five framework activities: communication, planning, modeling, construction, and deployment applicable to all software projects.
• Software engineering practice is a problem-solving activity that follows core principles.
• A wide array of software myths leads managers and practitioners astray as the collective knowledge of software/technologies needed to build it grows.

This content describes what software and hardware consists of. It also highlights the key differences between software and hardware. It emphasizes that software is engineered and doesn't wear out.