SOFTWARE

Computer software or simply software is any set of instructions that directs a computer to perform specific operations. Computer software consists of computer programs,libraries and related non-executable data (such as online documentation or digital media). Computer software is non-tangible, contrasted with computer hardware, which is the physical component of computers. Computer hardware and software require each other and neither can be realistically used without the other.

At the lowest level, executable code consists of machine language instructions specific to an individual processor—typically a central processing unit (CPU). A machine languageconsists of groups of binary values signifying processor instructions that change the state of the computer from its preceding state. For example, an instruction may change the value stored in a particular storage location inside the computer—an effect that is not directly observable to the user. An instruction may also (indirectly) cause something to appear on a display of the computer system—a state change which should be visible to the user. The processor carries out the instructions in the order they are provided, unless it is instructed to "jump" to a different instruction, or interrupted.

Software written in a machine language is known as "machine code". However, in practice, software is usually written in high-level programming languages that are easier and more efficient for humans to use (closer to natural language) than machine language. High-level languages are translated into machine language using a compiler or aninterpreter or a combination of the two. Software may also be written in a low-level assembly language, essentially, a vaguely mnemonic representation of a machine language using a natural language alphabet. Assembly language is translated into machine language using an assembler

List of software categories

Computer software can be put into categories based on common function, type, or field of use. There are three broad classifications:

• Application software is the general designation of computer programs for performing tasks. Application software may be general purpose (word processing, web browsers,...) or have a specific purpose (accounting, truck scheduling, ..) Application software contrast with system software.
• System software is a generic term referring to the computer programs used to start and run computer systems including diverse application software and networks.
• Computer programming tools, such as compilers and linker, are used to translate and combine computer program source code and libraries into executable RAMs (programs that will belong to one of the three said

.

Application software

► Free application software

► Astrology software

► Business software

► Chemical engineering software

► Software for children

► Communication software

► Computer-aided manufacturing software

► Data management software

► Desktop widgets

► Editing software

► Educational software

► Entertainment software

► Genealogy software

► Government software

► Graphics software

► Industrial software

► Knowledge representation software

► Language software

► Legal software

► Library and information science software

► Mobile applications

► Multimedia software

► Music software

► Personal information managers

► Computer programming tools

► Religious software

► Science software

► Simulation software

► Spreadsheet software

► Stagecraft software

► Application software suites

► Transport software

► Digital typography

► Video games

► Video software

► Word processors

► Workflow software

System software

► Free system software

► Boot loaders

► Compatibility layers

► Device drivers

► Firmware

► Graphical user interfaces

► Middleware

► Operating systems

► Utility software

► Windowing systems

Development software

► Free computer programming tools

► Bug and issue tracking software

► Build automation

► Code navigation tools

► Code search engines

► Compilers

► Compiling tools

► Computer-aided software engineering tools

► Data modeling tools

► Debuggers

► Desktop database application development tools

► Disassemblers

► Discontinued development tools

► Documentation generators

► Text editors

► EXE packers

► Formal methods tools

► Integrated development environments

► Java development tools

► JavaScript programming tools

► Linux programming tools

► Software-localization tools

► Mac OS Classic programming tools

► Microsoft development tools

► Mobile software programming tools

► OS X programming tools

► Profilers

► Programming language implementation

► Programming tools for Windows

► RISC OS programming tools

► Software testing tools

► Static program analysis tools

► UML tools

► Unix programming tools

► User interface builders

► Version control systems

► Web development software

► Computer programming tool stubs

APPLICATION SOFTWARE

An application program (app or application for short) is a computer program designed to perform a group of coordinated functions, tasks, or activities for the benefit of the user. Examples of an application include a word processor, a spreadsheet, an accounting application, a web browser, a media player, an aeronautical flight simulator, a console game or a photo editor. The collective nounapplication software refers to all applications collectively. This contrasts with system software, which is mainly involved with running the computer.

Terminology

In information technology, an application is a computer program designed to help people perform an activity. An application thus differs from an operating system (which runs a computer), a utility (which performs maintenance or general-purpose chores), and a programming tool (with which computer programs are created). Depending on the activity for which it was designed, an application can manipulate text, numbers, graphics, or a combination of these elements. Some application packages focus on a single task, such as word processing; others, called integrated software include several applications.

User-written software tailors systems to meet the user's specific needs. User-written software includes spreadsheet templates, word processor macros, scientific simulations, graphics and animation scripts. Even email filters are a kind of user software. Users create this software themselves and often overlook how important it is.

The delineation between system software such as operating systems and application software is not exact, however, and is occasionally the object of controversy. For example, one of the key questions in the United States v. Microsoft antitrust trial was whether Microsoft's Internet Explorer web browser was part of its Windows operating system or a separable piece of application software. As another example, the GNU/Linux naming controversy is, in part, due to disagreement about the relationship between the Linux kerneland the operating systems built over this kernel. In some types of embedded systems, the application software and the operating system software may be indistinguishable to the user, as in the case of software used to control a VCR, DVD player or microwave oven. The above definitions may exclude some applications that may exist on some computers in large organizations. For an alternative definition of an app: see Application Portfolio Management.

 Metonymy

The word "application", once used as an adjective, is not restricted to the "of or pertaining to application software" meaning). For example, concepts such as application programming interface (API), application server, application virtualization, application lifecycle management and portable application apply to all computer programs alike, not just application software.

Apps and killer apps

Some applications are available in versions for several different platforms; others have narrower requirements and are thus called, for example, a Geography application for Windows, an Android application for education, or Linux gaming. Sometimes a new and popular application arises which only runs on one platform, increasing the desirability of that platform. This is called a killer application or killer app.

In recent years, the shortened term "app" (coined in 1981 or earlier) has become popular to refer to applications for mobile devices such as smartphones and tablets, the shortened form matching their typically smaller scope compared to applications on PCs.

Classification

There are many different ways to divide up different types of application software, and several are explained here.

Since the development and near-universal adoption of the web, an important distinction that has emerged has been between web applications — written with HTML, JavaScript and other web-native technologies and typically requiring one to be online and running a web browser, and the more traditional native applications written in whatever languages are available for one's particular type of computer. There has been contentious debate in the computing community regarding web applications replacing native applications for many purposes, especially on mobile devices such as smart phones and tablets. Web apps have indeed greatly increased in popularity for some uses, but the advantages of applications make them unlikely to disappear soon, if ever. Furthermore, the two can be complementary, and even integrated.

Application software can also be seen as being either horizontal or vertical. Horizontal applications are more popular and widespread, because they are general purpose, for example word processors or databases. Vertical applications are niche products, designed for a particular type of industry or business, or department within an organization. Integrated suites of software will try to handle every specific aspect possible of, for example, manufacturing or banking systems, or accounting, or customer service.

There are many types of application software:

• An application suite consists of multiple applications bundled together. They usually have related functions, features and user interfaces, and may be able to interact with each other, e.g. open each other's files. Business applications often come in suites, e.g. Microsoft Office, Libre Office and iWork, which bundle together a word processor, a spreadsheet, etc.; but suites exist for other purposes, e.g. graphics or music.
• Enterprise software addresses the needs of an entire organization's processes and data flows, across several departments, often in a large distributed environment. Examples include enterprise resource planning systems, customer relationship management (CRM) systems and supply chain management software. Departmental Software is a sub-type of enterprise software with a focus on smaller organizations and/or groups within a large organization. (Examples include travel expense management and IT Helpdesk.)
• Enterprise infrastructure software provides common capabilities needed to support enterprise software systems. (Examples include databases, email servers, and systems for managing networks and security.)
• Information worker software lets users create and manage information, often for individual projects within a department, in contrast to enterprise management. Examples include time management, resource management, analytical, collaborative and documentation tools. Word processors, spreadsheets, email and blog clients, personal information system, and individual media editors may aid in multiple information worker tasks.
• Content access software is used primarily to access content without editing, but may include software that allows for content editing. Such software addresses the needs of individuals and groups to consume digital entertainment and published digital content. (Examples include media players, web browsers, and help browsers.)
• Educational software is related to content access software, but has the content and/or features adapted for use in by educators or students. For example, it may deliver evaluations (tests), track progress through material, or include collaborative capabilities.
• Simulation software simulates physical or abstract systems for either research, training or entertainment purposes.
• Media development software generates print and electronic media for others to consume, most often in a commercial or educational setting. This includes graphic-art software, desktop publishing software, multimedia development software, HTML editors, digital-animation editors, digital audio and video composition, and many others.
• Product engineering software is used in developing hardware and software products. This includes computer-aided design (CAD), computer-aided engineering (CAE), computer language editing and compiling tools, integrated development environments, and application programmer interfaces.
• Entertainment Software can refer to video games, screen savers, programs to display motion pictures or play recorded music, and other forms of entertainment which can be experienced through use of a computing device.

Applications can also be classified by computing platform such as a particular operating system, delivery network such as in cloud computing and Web 2.0 applications, or delivery devices such as mobile apps for mobile devices.

The operating system itself can be considered application software when performing simple calculating, measuring, rendering, and word processing tasks not used to control hardware via command-line interface or graphical user interface. This does not include application software bundled within operating systems such as a software calculator ortext editor.

SYSTEM SOFTWARE

System software (systems software) is computer software designed to provide services to other software. Examples of system software include operating systems,computational science software, game engines, industrial automation, and software as a service applications.

In contrast to system software, software that allows users to do things like create text documents, play games, listen to music, or web browsers to surf the web are called application software.

The line where the distinction should be drawn isn't always clear. All operating systems bundle application software. Such software is not considered system software when it can be uninstalled without affecting the functioning of other software. Exceptions could be e.g. web browsers such as Internet Explorer where Microsoft argued in court that it was system software that could not be uninstalled. Later examples are Chrome OS and Firefox OS where the browser functions as the only user interface and the only way to run programs (and other web browser can not be installed in their place), then they can well be argued to be (part of) the operating system and then system software.

Another borderline example is cloud based software. This software provides services to a software client (usually a web browser or a JavaScript application running in the web browser), not to the user directly, and is therefore systems software. It is also developed using system programming methodologies and systems programming languages. Yet from the perspective of functionality there is little difference between a word processing application and word processing web application.

Operating systems

The operating system (prominent examples being Microsoft Windows, Mac OS X and Linux), allows the parts of a computer to work together by performing tasks like transferring data between memory and disks or rendering output onto a display device. It provides a platform (hardware abstraction layer) to run high-level system software and application software.

A kernel is the core part of the operating system that defines an API for applications programs (including some system software) and an interface to device drivers.

Device drivers, including also computer BIOS and device firmware, provide basic functionality to operate and control the hardware connected to or built into the computer.

A user interface "allows users to interact with a computer. Either a command-line interface (CLI) or, since the 1980s a graphical user interface (GUI). Since this is the part of the operating system the user directly interacts with, it may be considered an application and therefore not a system software.

Utility software

For historical reasons, some organizations use the term systems programmer to describe a job function which would be more accurately termed systems administrator. Software tools these employees use are then called system software. This so called Utility software helps to analyze, configure, optimize and maintain the computer, such as virus protection. In some publications, the term system software also includes software development tools (like a compiler, linker or debugger).

SYSTEM PROGRAMMING

System programming (or systems programming) is the activity of programming computer system software. The primary distinguishing characteristic of systems programming when compared to application programming is that application programming aims to produce software which provides services to the user directly (e.g. word processor), whereas systems programming aims to produce software and software platforms which provide services to other software, are performance constrained, or usually both (e.g. operating systems, computational science applications, game engines and AAA video games, industrial automation, and software as a service applications).

System programming requires a great degree of hardware awareness. Its goal is to achieve efficient use of available resources, either because the software itself is performance critical (AAA video games) or because even small efficiency improvements directly transform into significant monetary savings for the service provider (cloud based word processors).

Overview

The following attributes characterize systems programming:

• The programmer will make assumptions about the hardware and other properties of the system that the program runs on, and will often exploit those properties, for example by using an algorithm that is known to be efficient when used with specific hardware.
• Usually a low-level programming language or programming language dialect is used that:
  • can operate in resource-constrained environments
  • is very efficient and has little runtime overhead
  • has a small runtime library, or none at all
  • allows for direct and "raw" control over memory access and control flow
  • lets the programmer write parts of the program directly in assembly language
• Often systems programs cannot be run in a debugger. Running the program in a simulated environment can sometimes be used to reduce this problem.

Systems programming is sufficiently different from application programming that programmers tend to specialize in one or the other.

In system programming, often limited programming facilities are available. The use of automatic garbage collection is not common and debugging is sometimes hard to do. The run time library, if available at all, is usually far less powerful, and does less error checking. Because of those limitations, monitoring and logging are often used; operating systems may have extremely elaborate logging subsystems.

Implementing certain parts in operating systems and networking requires systems programming, for example implementing Paging (Virtual Memory) or a device driver for an operating system.

History

Originally systems programmers invariably wrote in assembly language. Experiments with hardware support in high level languages in the late 1960s led to such languages as PL/S, BLISS, BCPL, and extended ALGOL for Burroughs large systems. Forth also has applications as a systems language. In the 1980s, C became ubiquitous, aided by the growth of Unix. More recently C++ has seen some use, for instance a subset of it is used in the I/O Kit drivers of Mac OS X.

Alternate usage

For historical reasons, some organizations use the term systems programmer to describe a job function which would be more accurately termed systems administrator. This is particularly true in organizations whose computer resources have historically been dominated by mainframes, although the term is even used to describe job functions which do not involve mainframes. This usage arose because administration of IBM mainframes often involved the writing of custom assembler code (IBM's Basic Assembly Language (BAL)), which integrated with the Operating System such as OS/MVS, DOS/VSE or VM/CMS. Indeed, some IBM software products had substantial code contributions from customer programming staff. This type of programming is progressively less common, but the term systems programmer is still the de facto job title for staff directly administering IBM mainframes.

SOFTWARE DEVELOPMENT

Software development is the process of computer programming, documenting, testing, and bug fixing involved in creating and maintaining applications and frameworks involved in a software release life cycle and resulting in a software product. The term refers to a process of writing and maintaining the source code, but in a broader sense of the term it includes all that is involved between the conception of the desired software through to the final manifestation of the software, ideally in a planned and structured process.Therefore, software development may include research, new development, prototyping, modification, reuse, re-engineering, maintenance, or any other activities that result in software products.

Software can be developed for a variety of purposes, the three most common being to meet specific needs of a specific client/business (the case with custom software), to meet a perceived need of some set of potential users (the case with commercial and open source software), or for personal use (e.g. a scientist may write software to automate a mundane task). Embedded software development, that is, the development of embedded software such as used for controlling consumer products, requires the development process to be integrated with the development of the controlled physical product. System software underlies applications and the programming process itself, and is often developed separately.

The need for better quality control of the software development process has given rise to the discipline of software engineering, which aims to apply the systematic approach exemplified in the engineering paradigm to the process of software development.

There are many approaches to software project management, known as software development life cycle models, methodologies, processes, or models. The waterfall model is a traditional version, contrasted with the more recent innovation of agile software development

Methodologies

A software development process (also known as a software development methodology, model, or life cycle) is a framework that is used to structure, plan, and control the process of developing information systems. A wide variety of such frameworks have evolved over the years, each with its own recognized strengths and weaknesses. There are several different approaches to software development: some take a more structured, engineering-based approach to developing business solutions, whereas others may take a more incremental approach, where software evolves as it is developed piece-by-piece. One system development methodology is not necessarily suitable for use by all projects. Each of the available methodologies is best suited to specific kinds of projects, based on various technical, organizational, project and team considerations.

Most methodologies share some combination of the following stages of software development:

• Analyzing the problem
• Market research
• Gathering requirements for the proposed business solution
• Devising a plan or design for the software-based solution
• Implementation (coding) of the software
• Testing the software
• Deployment
• Maintenance and bug fixing

These stages are often referred to collectively as the software development lifecycle, or SDLC. Different approaches to software development may carry out these stages in different orders, or devote more or less time to different stages. The level of detail of the documentation produced at each stage of software development may also vary. These stages may also be carried out in turn (a “waterfall” based approach), or they may be repeated over various cycles or iterations (a more "extreme" approach). The more extreme approach usually involves less time spent on planning and documentation, and more time spent on coding and development of automated tests. More “extreme” approaches also promote continuous testing throughout the development lifecycle, as well as having a working (or bug-free) product at all times. More structured or “waterfall” based approaches attempt to assess the majority of risks and develop a detailed plan for the software before implementation (coding) begins, and avoid significant design changes and re-coding in later stages of the software development life cycle planning.

There are significant advantages and disadvantages to the various methodologies, and the best approach to solving a problem using software will often depend on the type of problem. If the problem is well understood and a solution can be effectively planned out ahead of time, the more "waterfall" based approach may work the best. If, on the other hand, the problem is unique (at least to the development team) and the structure of the software solution cannot be easily envisioned, then a more "extreme" incremental approach may work best.

Software development activities

Identification of need

The sources of ideas for software products are legion. These ideas can come from market research including the demographics of potential new customers, existing customers, sales prospects who rejected the product, other internal software development staff, or a creative third party. Ideas for software products are usually first evaluated by marketing personnel for economic feasibility, for fit with existing channels distribution, for possible effects on existing product lines, required features, and for fit with the company's marketing objectives. In a marketing evaluation phase, the cost and time assumptions become evaluated. A decision is reached early in the first phase as to whether, based on the more detailed information generated by the marketing and development staff, the project should be pursued further.

Students of engineering learn engineering and are rarely exposed to finance or marketing. Students of marketing learn marketing and are rarely exposed to finance or engineering. Most of us become specialists in just one area. To complicate matters, few of us meet interdisciplinary people in the workforce, so there are few roles to mimic. Yet, software product planning is critical to the development success and absolutely requires knowledge of multiple disciplines.

Because software development may involve compromising or going beyond what is required by the client, a software development project may stray into less technical concerns such as human resources, risk management, intellectual property, budgeting, crisis management, etc. These processes may also cause the role of business development to overlap with software development.

Planning

Planning is an objective of each and every activity, where we want to discover things that belong to the project. An important task in creating a software program is extracting there quirements or requirements analysis. Customers typically have an abstract idea of what they want as an end result, but do not know what software should do. Skilled and experienced software engineers recognize incomplete, ambiguous, or even contradictory requirements at this point. Frequently demonstrating live code may help reduce the risk that the requirements are incorrect.

Once the general requirements are gathered from the client, an analysis of the scope of the development should be determined and clearly stated. This is often called a scope document.

Certain functionality may be out of scope of the project as a function of cost or as a result of unclear requirements at the start of development. If the development is done externally, this document can be considered a legal document so that if there are ever disputes, any ambiguity of what was promised to the client can be clarified.

Designing

Once the requirements are established, the design of the software can be established in a software design document. This involves a preliminary, or high-level design of the main modules with an overall picture (such as a block diagram) of how the parts fit together. The language, operating system, and hardware components should all be known at this time. Then a detailed or low-level design is created, perhaps with prototyping as proof-of-concept or to firm up requirements.

Implementation, testing and documenting

Implementation is the part of the process where software engineers actually program the code for the project.

Software testing is an integral and important phase of the software development process. This part of the process ensures that defects are recognized as soon as possible. In some processes, generally known as test-driven development, tests may be developed just before implementation and serve as a guide for the implementation's correctness.

Documenting the internal design of software for the purpose of future maintenance and enhancement is done throughout development. This may also include the writing of an API, be it external or internal. The software engineering process chosen by the developing team will determine how much internal documentation (if any) is necessary. Plan-driven models (e.g., Waterfall) generally produce more documentation than Agile models.

Deployment and maintenance

Deployment starts directly after the code is appropriately tested, approved for release, and sold or otherwise distributed into a production environment. This may involve installation, customization (such as by setting parameters to the customer's values), testing, and possibly an extended period of evaluation.

Software training and support is important, as software is only effective if it is used correctly.

Maintaining and enhancing software to cope with newly discovered faults or requirements can take substantial time and effort, as missed requirements may force redesign of the software.

BUSINESS PROCESS AND DATA MODELING

Graphical representation of the current state of information provides a very effective means for presenting information to both users and system developers.

example of the interaction between business process and data models.

• A business model illustrates the functions associated with the business process being modeled and the organizations that perform these functions. By depicting activities and information flows, a foundation is created to visualize, define, understand, and validate the nature of a process.
• A data model provides the details of information to be stored, and is of primary use when the final product is the generation of computer software code for an application or the preparation of a functional specification to aid a computer software make-or-buy decision. See the figure on the right for an example of the interaction between business process and data models.

Usually, a model is created after conducting an interview, referred to as business analysis. The interview consists of a facilitator asking a series of questions designed to extract required information that describes a process. The interviewer is called a facilitator to emphasize that it is the participants who provide the information. The facilitator should have some knowledge of the process of interest, but this is not as important as having a structured methodology by which the questions are asked of the process expert. The methodology is important because usually a team of facilitators is collecting information across the facility and the results of the information from all the interviewers must fit together once completed.

The models are developed as defining either the current state of the process, in which case the final product is called the "as-is" snapshot model, or a collection of ideas of what the process should contain, resulting in a "what-can-be" model. Generation of process and data models can be used to determine if the existing processes and information systems are sound and only need minor modifications or enhancements, or if re-engineering is required as a corrective action. The creation of business models is more than a way to view or automate your information process. Analysis can be used to fundamentally reshape the way your business or organization conducts its operations.

Computer-aided software engineering

Computer-aided software engineering (CASE), in the field software engineering is the scientific application of a set of software tools and methods to the development of software which results in high-quality, defect-free, and maintainable software products. It also refers to methods for the development of information systems together with automated tools that can be used in the software development process. The term "computer-aided software engineering" (CASE) can refer to the software used for the automated development of systems software, i.e., computer code. The CASE functions include analysis, design, and programming. CASE tools automate methods for designing, documenting, and producing structured computer code in the desired programming language.

Two key ideas of Computer-aided Software System Engineering (CASE) are:

• Foster computer assistance in software development and or software maintenance processes, and
• An engineering approach to software development and or maintenance.

Typical CASE tools exist for configuration management, data modeling, model transformation, refactoring, source code generation.