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Arithmetic logic unit

Arithmetic logic unit

In Computing, associate degree Arithmetic Logic Unit (ALU) could be a combinative Digital Circuit That Performs Arithmetic And Bitwise Operations On whole number Binary Numbers.

this is often In distinction To A Floating-Point Unit (FPU), that Operates On Floating purpose Numbers. it’s A basic Building Block of the many kinds of Computing Circuits, as well as The Central process Unit (CPU) Of Computers, FPUs, And Graphics process Units (GPUs).

Arithmetic logic unit
Arithmetic logic unit

The Inputs To associate degree ALU area unit the info To Be Operated On, referred to as Operands, And A Code Indicating The Operation To Be Performed; The ALU’s Output is that the results of The Performed Operation. In several styles, The ALU conjointly Has standing Inputs Or Outputs, Or Both, that Convey data a couple of Previous Operation Or the present Operation, severally, Between The ALU And External standing Registers.

Signals:

An Arithmetic logic unit encompasses a style of Input associate degreed Output Nets, that area unit The Electrical Conductors wont to Convey Digital Signals Between The ALU And External electronic equipment. once associate degree ALU is working, External Circuits Apply Signals To The ALU Inputs And, In Response, The ALU Produces And Conveys Signals To External electronic equipment Via Its Outputs.

Data

A Basic ALU Has 3 Parallel information Buses Consisting Of 2 Input Operands (A And B) And A Result Output (Y). every information Bus could be a cluster Of Signals That Conveys One Binary whole number range. Typically, The A, B And Y Bus Widths (The range Of Signals Comprising every Bus) area unit Identical And Match The Native Word Size Of The External electronic equipment (E.G., The Encapsulating processor Or different Processor).

Opcode

The Opcode Input could be a Parallel Bus That Conveys To The ALU associate degree Operation choice Code, that Is associate degree Enumerated worth That Specifies the required Arithmetic Or logical operation To Be Performed By The ALU.

The Opcode Size (Its Bus Width) Determines the most range of various Operations The ALU will Perform; for instance, A Four-Bit Opcode will Specify Up To Sixteen totally different ALU Operations. Generally, associate degree ALU Opcode isn’t a similar As A Machine Language Opcode, tho’ In Some Cases it should Be Directly Encoded As a touch Field inside A Machine Language Opcode.

Status:
Outputs

The standing Outputs area unit varied Individual Signals That Convey Supplemental data concerning The results of the present ALU Operation. general ALUs ordinarily Have standing Signals Such As:

  • Carry-Out, that Conveys The Carry ensuing From associate degree Addition Operation, The Borrow ensuing From A Subtraction Operation, Or The Overflow Bit ensuing From A Binary Shift Operation.
  • Zero, that Indicates All Bits Of Y area unit Logic Zero.
  • Negative, that Indicates The results of associate degree operation Is Negative.
  • Overflow, that Indicates The results of associate degree operation Has Exceeded The Numeric vary Of Y.
  • Parity, that Indicates whether or not an excellent Or Odd range Of Bits In Y area unit Logic One.

At the tip of every ALU Operation, The standing Output Signals area unit typically hold on In External Registers to form Them out there For Future ALU Operations (E.G., To Implement Multiple-Precision Arithmetic) Or For dominant Conditional Branching. the gathering Of Bit Registers That Store The standing Outputs area unit usually Treated As one, Multi-Bit Register, that Is cited because the “Status Register” Or “Condition Code Register”.

Inputs

The standing Inputs enable extra data To Be created out there To The ALU once activity associate degree Operation. Typically, this is often one “Carry-In” Bit that’s The hold on Carry-Out From A Previous ALU Operation.

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