# Combinational Logic

In digital circuit theory, combinational logic (sometimes also referred to as combinatorial logic or time-independent logic ) is a type of digital logic which is implemented by boolean circuits, where the output is a pure function of the present input only. This is in contrast to sequential logic, in which the output depends not only on the present input but also on the history of the input. In other words, sequential logic has memory while combinational logic does not.

Combinational logic is used in computer circuits to do boolean algebra on input signals and on stored data. Practical computer circuits normally contain a mixture of combinational and sequential logic. For example, the part of an arithmetic logic unit, or ALU, that does mathematical calculations is constructed using combinational logic. Other circuits used in computers, such as half adders, full adders, half subtractors, full subtractors, multiplexers, demultiplexers, encoders and decoders are also made by using combinational logic.

### Other articles related to "logic, combinational logic":

Digital Technology - Construction - Structure of Digital Systems
... Engineers use many methods to minimize logic functions, in order to reduce the circuit's complexity ... The most widely used simplification is a minimization algorithm like the Espresso heuristic logic minimizer within a CAD system, although historically ... The classical way to represent a digital circuit is with an equivalent set of logic gates ...
Algorithmic State Machine - Datapath
... shift register, a counter, or a register preceded by a combinational logic block ... The combinational logic block associated with a register may implement an adder, subtracter, multiplexer, or some other type of combinational logic function ...
Quality Of Results - Current Trends in EDA
... a number representing the ratio between the area required by a combinational logic block and the area required by a simple logic gate, this number being often referred to as "relative density of ... of five will generally be accepted as a good quality of result – relative density of combinational logic component – while a relative density of fifty will indicate severe design problems (routability ...
Combinational Logic - Terminology
... Some people claim that the term "combinatorial logic" is preferred over "combinational logic", although others make the opposite recommendation ...
Sequential Logic
... In digital circuit theory, sequential logic is a type of logic circuit whose output depends not only on the present value of its input signals but on the past history ... This is in contrast to combinational logic, whose output is a function of only the present input ... That is, sequential logic has state (memory) while combinational logic does not ...

### Famous quotes containing the word logic:

“... We need the interruption of the night
To ease attention off when overtight,
To break our logic in too long a flight,
And ask us if our premises are right.”
Robert Frost (1874–1963)