Computer
software
Computer software (or
simply software) is that
part of a computer system that
consists of encoded information
(or computer instructions), as
opposed to the physical computer
equipment (hardware)
which is used to store and
process this information. The
term is roughly synonymous with
computer program but is more
generic in scope.
The term "software" was first
used in this sense by
John W. Tukey in
1957. In
computer science and
software engineering,
computer software is all
information processed by
computer systems,
programs and
data. The concept of
software was first proposed by
Alan Turing in an essay.
Relationship to hardware
Computer software is so
called in contrast to
computer hardware, which is
the physical substrate 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, and
operating system. The
machine language consists of
groups of binary values
signifying processor
instructions and data, 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 to
obtain a particular result. It
is generally written in
'high-level 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.
Relationship to data
Software has historically
been considered an intermediary
between electronic hardware and
data, which latter the
hardware processes according
to the sequence of instructions
defined by the software. As
computational science becomes
increasingly complex, the
distinction between software and
data becomes less precise. Data
has generally been considered as
either the output or input of
executed software. However, data
is not the only possible output
or input. For example, (system)
configuration information may
also be considered input,
although not necessarily
considered data (and certainly
not applications data). The
output of a particular piece of
executed software may be the
input for another executed piece
of software. Therefore, software
may be considered an interface
between hardware, data, and/or
(other) software.
System, application and
programming software
Practical computer systems
divide software into three major
classes:
system software,
application software and
programming software,
although the distinction is
somewhat 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.
-
Application software
allows humans to accomplish
one or more specific
tasks. Typical
applications include
office suites,
business software,
educational software,
databases and
computer games. Most
contermporary application
software uses a
graphical user interface
(GUI), for humans to
interact with the data, but
a large portion of the
business world still uses
powerful
legacy systems written
before the development of
GUI, and a lot of computing
occurs without direct human
interaction.
-
Programming software
usually provides some useful
tools to help
programmer to write
computer programs and
software using different
programming language in
a more convenient way. The
tools include
text editor,
compiler,
interpreter,
linker,
debugger, and so on.
Integrated development
environment (IDE) merges
those tools in a software
bundle, and programmer
may not need to type a lot
of
commands for compiling,
interpreter, debugging,
tracing, and etc., because
IDE mostly has a GUI.
Software program and library
Software program is usually
the directly
executable part of a
software.
Software libraries can
include software components used
by stand-alone programs, but
which cannot be executed on
their own. Thus, programs can
include standard routines that
are common to many programs,
extracted from the libraries,
but libraries can also include
stand-alone programs. Depending
on
operating system, a program
can be called by another
program, by a human being, and
can call another program.
Three layers of software
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
basic input-output system
(often described as
firmware rather than
software),
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, 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. 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.
See also:
Software architecture.
Software creation
Look back to
Computer software
Software operation
Computer software has to be
"loaded" into the
computer's storage (also
known as memory and
RAM).
Once the software is loaded,
the computer is able to operate
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
flow of instructions.
Kinds of software by
operation:
computer program as
executable,
source code or
script,
configuration.
Software 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.
Software patents
The issue of
software patents is very
controversial, since while
patents protect the ideas of
"inventors",
they are widely believed to
hinder
software development. See
Hacker ethic
See also
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