# Operator Representations The C API provides various data structures for representing fermionic operators in different bases. | [`QfFermionOperator`](qf-ferm-op.html.md#c.QfFermionOperator) | An operator in the basis of the second-quantization creation
and annihilation operators. | |------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------| | [`QfMajoranaOperator`](qf-maj-op.html.md#c.QfMajoranaOperator) | An operator in the basis of Majorana fermions. | | [`QfEdgeVertexOperator`](qf-edge-op.html.md#c.QfEdgeVertexOperator) | An operator in the basis of the edge and vertex operators. | | [`QfTransferVertexOperator`](qf-transfer-op.html.md#c.QfTransferVertexOperator) | An operator in the basis of the transfer and vertex
operators. |