What is Software?

The product that software professionals build and then support over the long term.

Software encompasses (1) instructions (computer programs) that when executed provide desired features, function, and performance; (2) data structures that enable the programs to adequately store and manipulate information and (3) documentation that describes the operation and use of the programs.

Software products

• Generic products -Stand-alone systems that are marketed and sold to any customer who wishes to buy them. 

• Examples – PC software such as editing, graphics programs, project management tools; CAD software; software for specific markets such as appointments systems for dentists. 

• Customized products -Software that is commissioned by a specific customer to meet their own needs. 

• Examples – embedded control systems, air traffic control software, traffic monitoring systems.

Why is Software Important?

• The economies of ALL developed nations are dependent on software. 
• More and more systems are software controlled ( transportation, medical, telecommunications, military, industrial, entertainment,) 
• Software engineering is concerned with theories, methods, and tools for professional software development. 
• Expenditure on software represents a 
• significant fraction of GNP in all developed countries.

Software costs

• Software costs often dominate computer system costs. The costs of software on a PC are often greater than the hardware cost. 
• Software costs more to maintain than it does to develop. For systems with a long life, maintenance costs may be several times development costs. Software engineering is concerned with cost-effective software development

Features of Software?

Its characteristics that make it different from other things human being build.

Features of such logical system:

• Software is developed or engineered, it is not manufactured in the classical sense which has quality problem. 
• Software doesn't "wear out.” but it deteriorates (due to change). Hardware has bathtub curve of failure rate ( high failure rate in the beginning, then drop to steady state, then cumulative effects of dust, vibration, abuse occurs). Although the industry is moving toward component-based construction (e.g. standard screws and off-the-shelf integrated circuits), most software continues to be custom-built. Modern reusable components encapsulate data and processing into software parts to be reused by different programs. E.g. graphical user interface, window, pull-down menus in library etc.

Wear vs. Deterioration

                       Wear vs. Deterioration

Software Applications

• System software:  such as compilers, editors, file management utilities Application software: stand-alone programs for specific needs. Engineering/scientific software: Characterized by “number crunching”algorithms. such as automotive stress analysis, molecular biology, orbital dynamics etc
• Embedded software :resides within a product or system. (key pad control of a microwave oven, digital function of dashboard display in a car) 
•  Product-line software :focus on a limited marketplace to address mass consumer market. (word processing, graphics, database management) 
• WebApps: (Web applications) network-centric software. As web 2.0 emerges, more sophisticated computing environments is supported integrated with remote database and business applications. 
• AI :software uses non-numerical algorithm to solve complex problem. Robotics, expert system, pattern recognition game playing

Software—New Categories

• Open world computing—pervasive, ubiquitous, distributed computing due to wireless networking. How to allow mobile devices, personal computer, enterprise system to communicate across the vast network. 
• Netsourcing—the Web as a computing engine. How to architect simple and sophisticated applications to target end-users worldwide. 
• Open source—”free” source code open to the computing community (a blessing, but also a potential curse!) 

1. Data mining 
2. Grid computing 
3. Cognitive machines 
4. Software for nanotechnologies

          Software Engineering Definition

The seminal definition: Software engineering is the establishment and use of sound engineering principles in order to obtain economically software that is reliable and works efficiently on real machines

           The IEEE definition:

 Software Engineering: (1) The application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software; that is, the application of engineering to software. (2) The study of approaches as in (1).

Importance of Software Engineering

• More and more, individuals and society rely on advanced software systems. We need to be able to produce reliable and trustworthy systems economically and quickly. 
• It is usually cheaper, in the long run, to use software engineering methods and techniques for software systems rather than just write the programs as if it was a personal programming project. For most types of system, the majority of costs are the costs of changing the software after it has gone into use.

A Layered Technology

                       

• Any engineering approach must rest on an organizational commitment to quality which fosters a continuous process improvement culture. 
• Process layer as the foundation defines a framework with activities for the effective delivery of software engineering technology. Establish the context where products (model, data, report, and forms) are produced, milestone are established, quality is ensured and change is managed. 
• Method provides technical how-tos for building software. It encompasses many tasks including communication, requirement analysis, design modeling, program construction, testing, and support. 
• Tools provide automated or semi-automated support for the process and methods.

Software Process

• A process is a collection of activities, actions, and tasks that are performed when some work product is to be created. It is not a rigid prescription for how to build computer software. Rather, it is an adaptable approach that enables the people doing the work to pick and choose the appropriate set of work actions and tasks. 
• The purpose of the process is to deliver software in a timely manner and with sufficient quality to satisfy those who have sponsored its creation and those who will use it.

Five Activities of a Generic Process framework

• Communication: communicate with customer to understand objectives and gather requirements 
• Planning: creates a “map” defines the work by describing the tasks, risks and resources, work products and work schedule. 
• Modeling: Create a “sketch”, what it looks like architecturally, how the constituent parts fit together and other characteristics. 
• Construction: code generation and the testing. 
• Deployment: Delivered to the customer who evaluates the products and provides feedback based on the evaluation. 

• These five framework activities can be used to all software development regardless of the application domain, size of the project, complexity of the efforts etc, though the details will be different in each case.

• For many software projects, these framework activities are applied iteratively as a project progresses. Each iteration produces a software increment that provides a subset of overall software features and functionality

Umbrella Activities

Complement the five process framework activities and help team manage and control progress, quality, change, and risk.

• Software project tracking and control: assess progress against the plan and take actions to maintain the schedule. 
• Risk management: assesses risks that may affect the outcome and quality. 
• Software quality assurance: defines and conduct activities to ensure quality. 
• Technical reviews: assesses work products to uncover and remove errors before going to the next activity. 
• Measurement: define and collects process, project, and product measures to ensure stakeholder’s needs are met. 
• Software configuration management: manage the effects of change throughout the software process. 
• Reusability management: defines criteria for work product reuse and establishes mechanism to achieve reusable components. 
• Work product preparation and production: create work products such as models, documents, logs, forms and lists.