Software, consisting of programs, enables a computer to perform specific tasks,
as opposed to its physical components (hardware) which can only do the tasks they
are mechanically designed for. The term includes application software such as word
processors which perform productive tasks for users, system software such as operating
systems, which interface with hardware to run the necessary services for user-interfaces
and applications, and middleware which controls and co-ordinates distributed systems.
Contents [hide]
1 Terminology
2 Relationship to computer hardware
3 Types
4 Program and library
5 Three layers
6 Creation
7 Operation
8 Quality and reliability
9 License
10 Patents
11 Ethics and rights for software users
12 See also
12.1 Computer programming
12.2 Software licenses
13 Footnotes
[edit] Terminology
The term "software" is sometimes used in a broader context to describe any electronic
media content which embodies expressions of ideas such as film, tapes, records,
etc.[1]
A screenshot of computer software - AbiWord.The term "software" as an instruction-procedural
programming source for scheduling instruction streams according to the von Neumann
machine paradigm should not be confused with Configware and Flowware, which are
programming sources for configuring the resources (structural "programming" by Configware)
and for scheduling the data streams (data-procedural programming by Flowware) of
the Anti machine paradigm of Reconfigurable Computing systems. This is an important
issue, since Computer Science is meanwhile a dual-paradigm world, due to the existence
of FPGAs and Reconfigurable Computing.
[edit] Relationship to computer hardware
Main article: Computer hardware
Computer software is so called in contrast to computer hardware, which encompasses
the physical interconnections and devices required to store and execute (or run)
the software. In computers, software is loaded into RAM and executed in the central
processing unit. At the lowest level, software consists of a machine language specific
to an individual processor. A machine language consists of groups of binary values
signifying processor instructions (object code), which change the state of the computer
from its preceding state. Software is an ordered sequence of instructions for changing
the state of the computer hardware in a particular sequence. It 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 compiled or interpreted into machine language object code. Software may also
be written in an assembly language, essentially, a mnemonic representation of a
machine language using a natural language alphabet. Assembly language must be assembled
into object code via an assembler.
The term "software" was first used in this sense by John W. Tukey in 1958.[2] In
computer science and software engineering, computer software is all computer programs.
The concept of reading different sequences of instructions into the memory of a
device to control computations was invented by Charles Babbage as part of his difference
engine. The theory that is the basis for most modern software was first proposed
by Alan Turing in his 1935 essay Computable numbers with an application to the Entscheidungsproblem.[3]
[edit] Types
Practical computer systems divide software systems into three major classes: system
software, programming software and application software, although the distinction
is arbitrary, and often blurred.
System software helps run the computer hardware and computer system. It includes
operating systems, device drivers, diagnostic tools, servers, windowing systems,
utilities and more. The purpose of systems software is to insulate the applications
programmer as much as possible from the details of the particular computer complex
being used, especially memory and other hardware features, and such accessory devices
as communications, printers, readers, displays, keyboards, etc.
Programming software usually provides tools to assist a programmer in writing computer
programs and software using different programming languages in a more convenient
way. The tools include text editors, compilers, interpreters, linkers, debuggers,
and so on. An Integrated development environment (IDE) merges those tools into a
software bundle, and a programmer may not need to type multiple commands for compiling,
interpreter, debugging, tracing, and etc., because the IDE usually has an advanced
graphical user interface, or GUI.
Application software allows end users to accomplish one or more specific (non-computer
related) tasks. Typical applications include industrial automation, business software,
educational software, medical software, databases, and computer games. Businesses
are probably the biggest users of application software, but almost every field of
human activity now uses some form of application software. It is used to automate
all sorts of functions.
[edit] Program and library
A program may not be sufficiently complete for execution by a computer. In particular,
it may require additional software from a software library in order to be complete.
Such a library may include software components used by stand-alone programs, but
which cannot work on their own. Thus, programs may include standard routines that
are common to many programs, extracted from these libraries. Libraries may also
include 'stand-alone' programs which are activated by some computer event and/or
perform some function (e.g., of computer 'housekeeping') but do not return data
to their calling program. Programs may be called by one to many other programs;
programs may call zero to many other programs.
[edit] Three layers
Starting in the 1980s, application software has been sold in mass-produced packages
through retailers.See also: Software architecture
Users often see things differently than programmers. People who use modern general
purpose computers (as opposed to embedded systems, analog computers, supercomputers,
etc.) usually see three layers of software performing a variety of tasks: platform,
application, and user software.
Platform software
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, and users may not realize that it exists or that they have a
choice to use different 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 almost always 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
User software tailors systems to meet the users specific needs. User software include
spreadsheet templates, word processor macros, scientific simulations, and scripts
for graphics and animations. 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 purchased
application packages, many users may not be aware of the distinction between the
purchased packages, and what has been added by fellow co-workers.
[edit] Creation
Main article: Computer programming
[edit] Operation
Computer software has to be "loaded" into the computer's storage (such as a hard
drive, memory, or RAM). Once the software is loaded, the computer is able to execute
the software. Computers operate by executing the computer program. 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.
Instructions may be performed sequentially, conditionally, or iteratively. Sequential
instructions are those operations that are performed one after another. Conditional
instructions are performed such that different sets of instructions execute depending
on the value(s) of some data. In some languages this is known as an "if" statement.
Iterative instructions are performed repetitively and may depend on some data value.
This is sometimes called a "loop." Often, one instruction may "call" another set
of instructions that are defined in some other program or module. When more than
one computer processor is used, instructions may be executed simultaneously.
A simple example of the way software operates is what happens when a user selects
an entry such as "Copy" from a menu. In this case, a conditional instruction is
executed to copy text from data in a 'document' area residing in memory, perhaps
to an intermediate storage area known as a 'clipboard' data area. If a different
menu entry such as "Paste" is chosen, the software may execute the instructions
to copy the text from the clipboard data area to a specific location in the same
or another document in memory.
Depending on the application, even the example above could become complicated. The
field of software engineering endeavors to manage the complexity of how software
operates. This is especially true for software that operates in the context of a
large or powerful computer system.
Currently, almost the only limitations on the use of computer software in applications
is the ingenuity of the designer/programmer. Consequently, large areas of activities
(such as playing grand master level chess) formerly assumed to be incapable of software
simulation are now routinely programmed. The only area that has so far proved reasonably
secure from software simulation is the realm of human art— especially, pleasing
music and literature.
Kinds of software by operation: computer program as executable, source code or script,
configuration.
[edit] Quality and reliability
Software reliability considers the errors, faults, and failures related to the creation
and operation of software.
See Software auditing, Software quality, Software testing, and Software reliability.
[edit] License
Software license gives the user the right to use the software in the licensed environment,
some software comes with the license when purchased off the shelf, or OEM license
when bundled with hardware. Software can also be in the form of freeware or shareware.
See also License Management.
[edit] Patents
The issue of software patents is controversial. Some believe that they hinder software
development, while others argue that software patents provide an important incentive
to spur software innovation. See software patent debate.
[edit] Ethics and rights for software users
Being a new part of society, the idea of what rights users of software should have
is not very developed. Some, such as the free software community, believe that software
users should be free to modify and redistribute the software they use. They argue
that these rights are necessary so that each individual can control their computer,
and so that everyone can cooperate, if they choose, to work together as a community
and control the direction that software progresses in. Others believe that software
authors should have the power to say what rights the user will get.
The former philosophy is somewhat derived from the "hacker ethic" that was common
in the 60s and 70s.
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