Software takes Dual role of Software and Software Engineering. It is a Product and at the same time a Vehicle for delivering a product. Software delivers the most important product of our time is called information.
Software is defined as :-
1. Instructions : Programs that when executed provide desired function, features, and performance
2. Data structures : Enable the programs to adequately manipulate information
3. Documents : Descriptive information in both hard copy and virtual forms that describes the operation and use of the programs.
Characteristics of software : Software has characteristics that are considerably different than those of hardware.
Software is developed or engineered, it is not manufactured in the Classical Sense.
Although some similarities exist between software development and hardware manufacture, the two activities are fundamentally different. In both the activities, high quality is achieved through good design, but the manufacturing phase for hardware can introduce quality problems that are nonexistent or easily corrected for software. Both the activities are dependent on people, but the relationship between people is totally varying. These two activities require the construction of a “product” but the approaches are different. Software costs are concentrated in engineering which means that software projects cannot be managed as if they were manufacturing.
Software doesn’t “Wear Out”
The following figure shows the relationship between failure rate and time. Consider the failure rate as a function of time for hardware. The relationship is called the bathtub curve, indicates that hardware exhibits relatively high failure rates early in its life, defects are corrected and the failure rate drops to a steady state level for some period of time. As time passes, however, the failure rate rises again as hardware components suffer from the cumulative effects of dust, vibration, abuse, temperature extremes, and many other environmental maladies. So, stated simply, the hardware begins to wear out. Software is not susceptible to the environmental maladies that cause hardware to wear out.
Although the industry is moving toward component based construction, most software continues to be custom built
A software component should be designed and implemented so that it can be reused in many different programs. Modern reusable components encapsulate both data and the processing that is applied to the data, enabling the software and software engineering to create new applications from reusable parts.
Software Application Domains
Seven Broad Categories of software are challenges for software engineers
System software : A collection of programs written to service other programs. Some system software (compilers, editors, and file management utilities)
Application software : Stand alone programs that solve a specific business need. Application software is used to control business functions in real time (point of sale transaction processing, real time manufacturing process control).
Engineering/scientific software : It has been characterized by “number crunching” algorithms. Applications range from astronomy to volcanology, from automotive stress analysis to space shuttle orbital dynamics, and from molecular biology to automated manufacturing.
Embedded software : It resides within a product or system and is used to implement and control features and functions for the end user and for the system itself. Embedded software can perform limited and esoteric functions (key pad control for a microwave oven) or provide significant function and control capability (digital functions in an automobile such as fuel control, dashboard displays, and braking systems).
Product line software : Designed to provide a specific capability for use by many different customers. Product-line software can focus on a limited and esoteric marketplace (inventory control products) or address mass consumer markets (word processing, spreadsheets, computer graphics, multimedia, entertainment, database management, and personal and business financial applications).
Web applications : These Applications called “WebApps,” this network centric software category spans a wide array of applications. In their simplest form, WebApps can be little more than a set of linked hypertext files that present information using text and limited graphics.
.Artificial intelligence software : These makes use of non numerical algorithms to solve complex problems that are not amenable to computation or straightforward analysis. Applications within this area include robotics, expert systems, pattern recognition (image and voice), artificial neural networks, theorem proving, and game playing.
New Software Challenges
- Open world computing : Creating software to allow machines of all sizes to communicate with each other across vast networks (Distributed computing wireless networks)
- Netsourcing : Architecting simple and sophisticated applications that benefit targeted end user markets worldwide (the Web as a computing engine)
- Open Source : Distributing source code for computing applications so customers can make local modifications easily and reliably ( “free” source code open to the computing community)
- Legacy software is older programs that are developed decades ago.
- The quality of legacy software is poor because it has inextensible design, convoluted code, poor and nonexistent documentation, test cases and results that are not achieved.
As time passes legacy systems evolve due to following reasons:
- The software must be adapted to meet the needs of new computing environment or technology.
- The software must be enhanced to implement new business requirements.
- The software must be extended to make it interoperable with more modern systems or database
- The software must be re-architected to make it viable within a network environment.
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