Editing Adder (electronics) (section)

{{Short description|Digital circuit that produces sums from inputs}}
{{Sidebar arithmetic logic circuits|expand=Components|expand-components=Adder}}
An '''adder''', or '''summer''',<ref>{{cite book | last=Singh | first=Ajay Kumar | date=2010 |chapter=10. Adder and Multiplier Circuits |chapter-url={{GBurl|Gr023E8Kd5QC|p=321}} | title=Digital VLSI Design | publisher=Prentice Hall India | pages=321–344 | isbn=978-81-203-4187-6 | via=Google Books}}</ref> is a [[digital circuit]] that performs [[addition]] of numbers. In many [[computer]]s and other kinds of [[microprocessor|processor]]s, adders are used in the [[arithmetic logic units]] (ALUs). They are also used in other parts of the processor, where they are used to calculate [[address space|address]]es, [[database index|table indices]], [[increment and decrement operators]] and similar operations.

Although adders can be constructed for many [[number representation]]s, such as [[binary-coded decimal]] or [[excess-3]], the most common adders operate on [[binary number]]s.
In cases where [[two's complement]] or [[ones' complement]] is being used to represent [[negative number]]s, it is trivial to modify an adder into an [[adder–subtractor]].
Other [[signed number representations]] require more logic around the basic adder.