{"schemaVersion":1,"slug":"iec-subtracter","name":"IEC subtracter (P-Q)","kind":"symbol","abbreviation":"P-Q","aliases":["binary subtracter","P minus Q element","IEC subtractor"],"category":"logic-signals","drawingTypes":["Schematic"],"referenceFamilies":["IEC","Manufacturer"],"summary":"IEC arithmetic element marked P-Q that subtracts word Q from word P, with borrow handling.","description":["The subtracter qualifier is written P minus Q. Inputs are grouped as the P and Q words with binary weights and outputs give the difference, with borrow input and output terminals for cascading. TI's overview lists it with the adder and other arithmetic qualifiers.","Dedicated subtracter devices are uncommon; the function is often provided by an adder with an inverted input word or by an arithmetic logic unit. Functional diagrams and programmable logic documentation still use the P-Q element to state intent clearly.","The symbol does not say whether the result is signed or how negative results are represented. State that in the logic description."],"readingNotes":["P is the minuend and Q the subtrahend.","Check borrow terminals when cascading."],"drawingChecklist":["Mark the element P-Q.","Group and weight both words.","Describe the result representation."],"distinction":"The Σ adder adds P and Q; an ALU may perform either under mode control.","facts":[{"label":"Qualifier","value":"P-Q"},{"label":"Common implementation","value":"Adder with complemented input or ALU"},{"label":"Artwork scope","value":"Original educational illustration; consult the applicable standard and the selected device documentation for the exact graphic"}],"references":[{"sourceId":"s28-ti-ieee91-logic-symbols","relevance":"Lists P-Q as the subtracter qualifier."}],"related":["iec-full-adder","iec-arithmetic-logic-unit","binary-full-adder"],"artwork":"s28-iec-subtracter","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","symbolVariant":{"convention":"IEC","form":"Rectangular element with the P-Q qualifier","reference":"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."},"plainEnglish":{"title":"What does IEC subtracter (P-Q) mean?","introduction":"The subtracter additional drawing mark is written P minus Q. Inputs are grouped as the P and Q words with binary weights and outputs give the difference, with borrow input and output terminals for cascading. TI's overview lists it with the adder and other arithmetic qualifiers.","example":"Dedicated subtracter devices are uncommon; the function is often provided by an adder with an inverted input word or by an arithmetic logic unit. Functional diagrams and programmable logic documentation still use the P-Q element to state intent clearly.","drawings":"The symbol does not say whether the result is signed or how negative results are represented. State that in the logic description.","terms":[{"name":"Terminal","meaning":"An identified point where a conductor connects."},{"name":"Signal","meaning":"Electrical information passed between devices, rather than necessarily the main power supply."},{"name":"Schematic","meaning":"A drawing showing function and connections rather than physical appearance."}],"diagram":"flow","steps":["Identify the device and form","Read the connections and state","Check the equipment reference"],"caption":"A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.","sources":[{"label":"Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)","url":"https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf"}],"detail":"IEC arithmetic element marked P-Q that subtracts word Q from word P, with borrow handling. The Σ adder adds P and Q; an ALU may perform either under mode control.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/iec-subtracter","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/iec-subtracter.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"s28-ti-ieee91-logic-symbols","title":"Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)","publisher":"Texas Instruments","url":"https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf","type":"manufacturer","scope":"Public explanation of rectangular logic symbols, general qualifiers, input and output qualifiers, dependency notation, bistable elements and coders, consistent with IEC 617-12 work.","checkedOn":"2026-10-28","reuse":"link-only","relevance":"Lists P-Q as the subtracter qualifier."}]}