COMPUTER SOFTWARE, or simply SOFTWARE, is a part of a computer system that consists of data or computer instructions, in contrast to the physical hardware from which the system is built. In computer science and software engineering , computer software is all information processed by computer systems , programs and data. Computer software includes computer programs , libraries and related non-executable data , such as online documentation or digital media . Computer hardware and software require each other and neither can be realistically used on its own.
At the lowest level, executable code consists of machine language instructions specific to an individual processor —typically a central processing unit (CPU). A machine language consists 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 in 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 is interrupted (by now multi-core processors are dominant, where each core can run instructions in order; then, however, each application software runs only on one core by default, but some software has been made to run on many).
The majority of software is written in high-level programming
languages that are easier and more efficient for programmers to use
because they are closer than machine languages to natural languages .
High-level languages are translated into machine language using a
compiler or an interpreter or a combination of the two.
* 1 History
* 2 Types of software
* 2.1 Purpose, or domain of use * 2.2 Nature or domain of execution * 2.3 Programming tools
* 3.1 Architecture * 3.2 Execution * 3.3 Quality and reliability * 3.4 License * 3.5 Patents
* 4 Design and implementation * 5 Industry and organizations * 6 See also * 7 References * 8 External links
Main article: History of software
An outline (algorithm ) for what would have been the first piece of software was written by Ada Lovelace in the 19th century, for the planned Analytical Engine . However, neither the Analytical Engine nor any software for it were ever created.
The first theory about software—prior to creation of computers as we know them today—was proposed by Alan Turing in his 1935 essay _Computable numbers with an application to the Entscheidungsproblem_ (decision problem).
This eventually led to the creation of the twin academic fields of
computer science and software engineering, which both study software
and its creation.
However, prior to 1946, software as we now understand it—programs stored in the memory of stored-program digital computers—did not yet exist. The first electronic computing devices were instead rewired in order to "reprogram" them.
TYPES OF SOFTWARE
See also: List of software categories
On virtually all computer platforms, software can be grouped into a few broad categories.
PURPOSE, OR DOMAIN OF USE
Based on the goal, computer software can be divided into:
* APPLICATION SOFTWARE which is software that uses the computer system to perform special functions or provide entertainment functions beyond the basic operation of the computer itself. There are many different types of application software, because the range of tasks that can be performed with a modern computer is so large—see list of software . * SYSTEM SOFTWARE which is software that directly operates the computer hardware , to provide basic functionality needed by users and other software, and to provide a platform for running application software. System software includes:
* OPERATING SYSTEMS which are essential collections of software that manage resources and provides common services for other software that runs "on top" of them. Supervisory programs , boot loaders , shells and window systems are core parts of operating systems. In practice, an operating system comes bundled with additional software (including application software) so that a user can potentially do some work with a computer that only has one operating system. * DEVICE DRIVERS which operate or control a particular type of device that is attached to a computer. Each device needs at least one corresponding device driver; because a computer typically has at minimum at least one input device and at least one output device, a computer typically needs more than one device driver. * UTILITIES which are computer programs designed to assist users in the maintenance and care of their computers.
* MALICIOUS SOFTWARE or MALWARE which is software that is developed to harm and disrupt computers. As such, malware is undesirable. Malware is closely associated with computer-related crimes, though some malicious programs may have been designed as practical jokes .
NATURE OR DOMAIN OF EXECUTION
Desktop applications such as web browsers and
Microsoft Office ,
as well as smartphone and tablet applications (called "apps "). (There
is a push in some parts of the software industry to merge desktop
applications with mobile apps, to some extent.
Windows 8 , and later
Ubuntu Touch , tried to allow the same style of application user
interface to be used on desktops, laptops and mobiles.)
in web pages that are run directly inside the web browser when a web
page is loaded without the need for a web browser plugin. Software
written in other programming languages can also be run within the web
web browser plugin that supports that language is installed; the most
common example of the latter is
ActionScript scripts, which are
supported by the
* Server software , including:
* Plugins and extensions are software that extends or modifies the functionality of another piece of software, and require that software be used in order to function; * Embedded software resides as firmware within embedded systems , devices dedicated to a single use or a few uses such as cars and televisions (although some embedded devices such as wireless chipsets can _themselves_ be part of an ordinary, non-embedded computer system such as a PC or smartphone). In the embedded system context there is sometimes no clear distinction between the system software and the application software. However, some embedded systems run embedded operating systems , and these systems do retain the distinction between system software and application software (although typically there will only be one, fixed, application which is always run). * Microcode is a special, relatively obscure type of embedded software which tells the processor _itself_ how to execute machine code, so it is actually a lower level than machine code. It is typically proprietary to the processor manufacturer, and any necessary correctional microcode software updates are supplied by them to users (which is much cheaper than shipping replacement processor hardware). Thus an ordinary programmer would not expect to ever have to deal with it.
Main article: Programming tool
Programming tools are also software in the form of programs or
applications that software developers (also known as _programmers,
coders, hackers_ or _software engineers_) use to create, debug ,
maintain (i.e. improve or fix), or otherwise support software.
Users often see things differently from programmers. People who use modern general purpose computers (as opposed to embedded systems , analog computers and supercomputers ) usually see three layers of software performing a variety of tasks: platform, application, and user software.
* PLATFORM SOFTWARE The Platform includes the firmware , device drivers , an operating system , and typically a graphical user interface which, in total, allow a user to interact with the computer and its peripherals (associated equipment). Platform software often comes bundled with the computer. On a PC one will usually have the ability to change the platform software. * APPLICATION SOFTWARE Application software or Applications are what most people think of when they think of software. Typical examples include office suites and video games. Application software is often purchased separately from computer hardware. Sometimes applications are bundled with the computer, but that does not change the fact that they run as independent applications. Applications are usually independent programs from the operating system, though they are often tailored for specific platforms. Most users think of compilers, databases, and other "system software" as applications. * USER-WRITTEN SOFTWARE End-user development tailors systems to meet users' specific needs. User software include spreadsheet templates and word processor templates. Even email filters are a kind of user software. Users create this software themselves and often overlook how important it is. Depending on how competently the user-written software has been integrated into default application packages, many users may not be aware of the distinction between the original packages, and what has been added by co-workers.
Main article: Execution (computing)
Computer software has to be "loaded" into the computer\'s storage (such as the hard drive or memory ). Once the software has loaded, the computer is able to _execute_ the software. This involves passing instructions from the application software , through the system software, to the hardware which ultimately receives the instruction as machine code . Each instruction causes the computer to carry out an operation—moving data , carrying out a computation , or altering the control flow of instructions.
Data movement is typically from one place in memory to another. Sometimes it involves moving data between memory and registers which enable high-speed data access in the CPU. Moving data, especially large amounts of it, can be costly. So, this is sometimes avoided by using "pointers" to data instead. Computations include simple operations such as incrementing the value of a variable data element. More complex computations may involve many operations and data elements together.
QUALITY AND RELIABILITY
Software quality is very important, especially for commercial and
system software like
Microsoft Office ,
Microsoft Windows and
Many bugs are discovered and eliminated (debugged) through software
testing . However, software testing rarely—if ever—eliminates
every bug; some programmers say that "every program has at least one
more bug" (Lubarsky's Law). In the waterfall method of software
development, separate testing teams are typically employed, but in
newer approaches, collectively termed agile software development ,
developers often do all their own testing, and demonstrate the
software to users/clients regularly to obtain feedback.
Main article: Software license
The software's license gives the user the right to use the software in the licensed environment, and in the case of free software licenses , also grants other rights such as the right to make copies.
Proprietary software can be divided into two types:
* freeware , which includes the category of "free trial" software or "freemium " software (in the past, the term shareware was often used for free trial/freemium software). As the name suggests, freeware can be used free, although in the case of free trials or freemium software, this is sometimes only true for a limited period of time or with limited functionality. * software available for a fee, often inaccurately termed "commercial software ", which can only be legally used on purchase of a license.
Open source software , on the other hand, comes with a free software license , granting the recipient the rights to modify and redistribute the software.
DESIGN AND IMPLEMENTATION
Design and implementation of software varies depending on the complexity of the software. For instance, the design and creation of Microsoft Word took much more time than designing and developing Microsoft Notepad because the latter has much more basic functionality.
Data structures such as hash tables , arrays , and binary trees , and algorithms such as quicksort , can be useful for creating software.
Computer software has special economic characteristics that make its design, creation, and distribution different from most other economic goods.
A person who creates software is called a programmer , software engineer or software developer , terms that all have a similar meaning. More informal terms for programmer also exist such as "coder" and "HACKER" – although use of the latter word may cause confusion, because it is more often used to mean someone who illegally breaks into computer systems .
INDUSTRY AND ORGANIZATIONS
Main article: Software industry
A great variety of software companies and programmers in the world
comprise a software industry.
Non-profit software organizations include the Free Software
GNU Project and
Mozilla Foundation .