# IEC arithmetic logic unit (ALU)

Canonical URL: https://eloragrid.ai/symbols/iec-arithmetic-logic-unit
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: ALU
Drawing use: Schematic
Reference families: IEC, Manufacturer

## Symbol convention

Convention: IEC
Form: Rectangular element with ALU qualifier and mode-select inputs
Qualifying-symbol and dependency conventions as explained in TI's public overview of IEEE Std 91-1984, which incorporates IEC 617-12 work. Independent educational drawing; not certified IEC geometry or an IEC database identifier.

IEC element marked ALU, performing arithmetic or logic functions on two words as chosen by mode inputs.

## In plain English

### What does IEC arithmetic logic unit (ALU) mean?

The ALU additional drawing mark identifies an element that can perform several arithmetic and logic operations on input words P and Q. Function-select inputs use M dependency or a binary grouping to choose the operation, and outputs include the result, carry and often a P=Q flag. Because the function table is large, the symbol usually refers to a table on the drawing or in the datasheet.

### A simple example

ALU symbols appear in processor and controller block diagrams and in legacy logic boards. On a modern control drawing they mainly document programmable logic or explain how a processor module handles signals.

### What the drawings help you do

The ALU additional drawing mark does not list the operations. A function table is essential and should be referenced explicitly. Preserve the mode-select signal names and the carry interpretation when comparing the symbol with that table.

### This particular reference

IEC element marked ALU, performing arithmetic or logic functions on two words as chosen by mode inputs. The Σ element only adds; the ALU selects among many operations, including subtraction and logic functions.

### Terms

- Signal: Electrical information passed between devices, rather than necessarily the main power supply.
- Schematic: A drawing showing function and connections rather than physical appearance.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)](https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf)


## What it represents

The ALU qualifier identifies an element that can perform several arithmetic and logic operations on input words P and Q. Function-select inputs use M dependency or a binary grouping to choose the operation, and outputs include the result, carry and often a P=Q flag. Because the function table is large, the symbol usually refers to a table on the drawing or in the datasheet.
ALU symbols appear in processor and controller block diagrams and in legacy logic boards. On a modern control drawing they mainly document programmable logic or explain how a processor module handles signals.
The ALU qualifier does not list the operations. A function table is essential and should be referenced explicitly. Preserve the mode-select signal names and the carry interpretation when comparing the symbol with that table.

## How to read it

- Find the function table referenced by the mode inputs.
- Check carry and comparison outputs.

## Information to show or reference

- Mark the element ALU.
- Reference the function table.
- Show carry and flag outputs.

## Important distinction

The Σ element only adds; the ALU selects among many operations, including subtraction and logic functions.

## Facts

- Qualifier: ALU
- Function selection: Mode inputs referencing a table
- Artwork scope: Original educational illustration; consult the applicable standard and the selected device documentation for the exact graphic

## Public references

- [Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)](https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf) — Texas Instruments. Lists ALU as a general qualifier.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.