Side-by-side reference

Understand the difference.

Compare the meaning, drawing context and source references of two entries. A similar graphic or shared abbreviation does not establish equivalence.

First referenceCompare with

ALU

IEC

IEC arithmetic logic unit (ALU)

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.

Drawing use: Schematic
Application: Logic & signals
Reference family: IEC / Manufacturer
Form evidence: 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.

A distinction that matters

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

Full reference

IEC

IEC adder (Σ)

The adder qualifier is the capital sigma. Inputs are grouped into P and Q words with binary weights, plus a carry input CI; outputs give the sum with weights and a carry output CO. TI's overview lists Σ alongside P-Q for subtraction and CPG for look-ahead carry generation.

Drawing use: Schematic
Application: Logic & signals
Reference family: IEC / Manufacturer
Form evidence: Rectangular element with Σ qualifier, P and Q inputs, CI and CO. 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. The counterpart is the matching functional concept; no equivalence of every detailed standard graphic is asserted.

A distinction that matters

A subtracter carries the P-Q qualifier instead; Σ marks an adder.

Full reference

Original educational previews. Follow the source references on each full entry for the appropriate standard or selected product.