Input
Input is the term
denoting either an entrance or changes which are inserted into a
system and which activate/modify a
process. It is an abstract concept, used in the
modeling, system(s) design and system(s) exploitation. It is usually connected with other terms, for example:
- input variable(s)
- input parameter(s)
- input value(s)
- input signal
and also
- input device.
From the most general
systemics perspective, input is a subjective concept and depends on how the system is used. In such sense, the same system can have different inputs in different applications.
In the case of a process description/model, the concept input is closely connected with the concept
output. Here, what enters is called input and what exits is called output.
Example:For an abstract system
A(x,y,p), where
x,y are variables and
p is a parameter,
x may denote input (variable) and
y may denote the output for a process:
y = f(p,x), but, for another
goal/(system application), the system
A can be the
carrier of a process
x = g(p,y), where
y is an input and
x is an output, see
System-Process Relation.
Usually, in the modeling of a problem/process, input are these variables which are known and output are those unknown to us yet.
In different contexts,
input has several more concrete
domain-dependent meanings.
In
information processing,
input refers to either information received or the process of receiving it:
* In
human-computer interaction, input is the information produced by the
user with the purpose of controlling the
computer program. The
user interface determines what kinds of input the program accepts (for example,
control strings or text typed with keyboard and
mouse clicks).
* Input also comes from
networks and storage devices such as
disk drives.
In
control theory, the
inputs of a system are the signals that can be observed or affected that feed into the system. Specifically, inputs are differentiated from
states.
In
equity theory,
inputs are the skills, time, effort, expertise, experience or qualifications that an employee brings to his job.
In
economics, inputs refer to priced or unpriced resources used in a production process, and outputs refer to the priced or unpriced results of that process. Normally, inputs are regarded as costs, and outputs as products. Outputs may be valued gross (before deduction of costs from sales) or net (after deduction of costs from sales).
Input-output economics was popularised by the economist
Wassily Leontief who devised an ingenious system of input and output accounts and
matrices to analyse the flows of goods and services between different sectors of a national economy. In
national accounts an attempt is made to value national inputs and outputs according to consistent valuation principles, to measure the creation and distribution of wealth.
*
Output*
Input/output*
Gross output*
Net output
