# IEC magnitude comparator (COMP)

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

## Symbol convention

Convention: IEC
Form: Rectangular element with COMP qualifier and P, Q input groups
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.
Related representation: [Digital magnitude comparator](https://eloragrid.ai/symbols/digital-magnitude-comparator)

IEC COMP element comparing two binary words P and Q, with outputs for P>Q, P=Q and P<Q.

## In plain English

### What does IEC magnitude comparator (COMP) mean?

The IEC magnitude comparator is marked COMP. Its inputs are grouped as word P and word Q with binary weights, and its outputs are labelled P>Q, P=Q and P<Q. Cascading inputs carry the same labels in a separate group so that comparators can be chained for longer words.

### A simple example

Digital comparators appear in set-point logic, address matching and limit checking. A reviewer should confirm the bit order of P and Q, because a swapped weight produces a comparison that is correct only for some values.

### What the drawings help you do

The symbol does not indicate whether the comparison is for signed or unsigned numbers. Standard devices compare unsigned binary.

### This particular reference

IEC COMP element comparing two binary words P and Q, with outputs for P>Q, P=Q and P<Q. An analogue voltage comparator compares two voltages, not binary words.

### 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)
- [CD74HC85 — digital magnitude comparators](https://www.ti.com/product/CD74HC85)


## What it represents

The IEC magnitude comparator is marked COMP. Its inputs are grouped as word P and word Q with binary weights, and its outputs are labelled P>Q, P=Q and P<Q. Cascading inputs carry the same labels in a separate group so that comparators can be chained for longer words.
Digital comparators appear in set-point logic, address matching and limit checking. A reviewer should confirm the bit order of P and Q, because a swapped weight produces a comparison that is correct only for some values.
The symbol does not indicate whether the comparison is for signed or unsigned numbers. Standard devices compare unsigned binary.

## How to read it

- Check bit weights on both words.
- Cascade inputs are needed for words longer than one device.

## Information to show or reference

- Group and weight the P and Q inputs.
- Label all three outputs.
- Show cascade connections.

## Important distinction

An analogue voltage comparator compares two voltages, not binary words.

## Facts

- Qualifier: COMP
- Outputs: P>Q, P=Q, P<Q
- 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 COMP as the magnitude comparator qualifier.
- [CD74HC85 — digital magnitude comparators](https://www.ti.com/product/CD74HC85) — Texas Instruments. Magnitude comparator documentation.

## 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.