Software Applications, Software engineering, Process, Methods, and Tools, A Generic View of SE

Software may be applied in any situation for which a pre specified set of procedural steps (i.e., an algorithm) has been defined (notable exceptions to this rule are expert system software and neural network software).
Information content and determinacy are important factors in determining the nature of a software application. Content refers to the meaning and form of incoming and outgoing information.
It is somewhat difficult to develop meaningful generic categories for software applications.
The following software areas indicate the breadth of potential applications:
System software. System software is a collection of programs written to service other programs. Some system software (e.g., compilers, editors, and file management utilities) process complex, but determinate, information structures. Other systems applications (e.g., operating system components, drivers, telecommunications processors) process largely indeterminate data.

Real-time software. Software that monitors/analyzes/controls real-world events as they occur is called real time. Elements of real-time software include a data gathering component that collects and formats information from an external environment, an analysis component that transforms information as required by the application, a control/output component that responds to the external environment, and a monitoring component that coordinates all other components so that real-time response (typically ranging from 1 millisecond to 1 second) can be maintained.

Business software. Business information processing is the largest single software application area. Discrete "systems" (e.g., payroll, accounts receivable/payable, inventory) have evolved into management information system (MIS) software that accesses one or more large databases containing business information.

Engineering and scientific software. Engineering and scientific software have 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. Intelligent products have become commonplace in nearly every consumer and industrial market. Embedded software resides in read-only memory and is used to control products and systems for the consumer and industrial markets.
Examples of embedded software include those found in dedicated GPS devices, factory robots, some calculators and even modern smartwatches.

Personal computer software. The personal computer software market has burgeoned over the past two decades. Word processing, spreadsheets, computer graphics, multimedia, entertainment, database management, personal and business financial applications, external network, and database access are only a few of hundreds of applications.

Web-based software. The Web pages retrieved by a browser are software that incorporates executable instructions (e.g., CGI, HTML, Perl, or Java), and data (e.g., hypertext and a variety of visual and audio formats).
There are popular email programs like Yahoo and Gmail, and instant messaging services are web applications too

Artificial intelligence software. Artificial intelligence (AI) software makes use of non numerical algorithms to solve complex problems that are not amenable to computation or straightforward analysis.
Expert systems, also called knowledge based systems, pattern recognition (image and voice), artificial neural networks, theorem proving, and game playing are representative of applications within this category.
Voice assistants are the best AI examples in real life such as, Google Assistant, Alexa, or Siri. 

A definition proposed by Fritz Bauer [NAU69] at the seminal conference on the subject still serves as a basis for discussion:

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 [IEE93] has developed a more comprehensive definition when it states:

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).

The work associated with software engineering can be categorized into three generic phases, regardless of application area, project size, or complexity.
1. The definition phase focuses on what.
2. The development phase focuses on how.
3. The support phase focuses on change associated with error correction, adaptations required as the software's environment evolves, and changes due to enhancements brought about by changing customer requirements.