---
title: Operator Representations (latest version)
description: API reference for Operator Representations in the latest version of qiskit-fermions-c
source: https://quantum.cloud.ibm.com/docs/en/api/qiskit-fermions-c/qf-operators
---

# Operator Representations

The C API provides various data structures for representing fermionic operators in different bases.

|                                                                                                       |                                                                                          |
| ----------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------- |
| [`QfFermionOperator`](/docs/api/qiskit-fermions-c/qf-ferm-op#qffermionoperator "QfFermionOperator")   | An operator in the basis of the second-quantization creation and annihilation operators. |
| [`QfMajoranaOperator`](/docs/api/qiskit-fermions-c/qf-maj-op#qfmajoranaoperator "QfMajoranaOperator") | An operator in the basis of Majorana fermions.                                           |