# [Enums](@id structures-enums)
The members of the fundamental HiGHS enums are defined below. If `Enum` refers
to a particular enum, and `Member` to a particular member, the members are
available as follows.
* Python: `highspy.Enum.Member`
* C++: `Enum::Member`
Members for internal use only are not documented.
## HighsStatus
This is (part of) the return value of most HiGHS methods:
* `kError`: The method has exposed an error
* `kOk`: The method has completed successfully
* `kWarning`: The method has recovered from an unusual event, or has terminated
due to reaching a time or iteration limit
## MatrixFormat
This defines the format of a [HighsSparseMatrix](@ref):
* `kColwise`: The matrix is stored column-wise
* `kRowwise`: The matrix is stored row-wise
## ObjSense
This defines optimization sense of a [HighsLp](@ref):
* `kMinimize`: The objective is to be minimized
* `kMaximize`: The objective is to be maximized
## HighsVarType
This defines the feasible values of a variable within a model:
* `kContinuous`: The variable can take continuous values between its bounds
* `kInteger`: The variable must take integer values between its bounds
* `kSemiContinuous`: The variable must be zero or take continuous values between its bounds
* `kSemiInteger`: The variable must be zero or take integer values between its bounds
## HessianFormat
This defines the format of a [HighsHessian](@ref):
* `kTriangular`: The lower triangular component of the Hessian is stored column-wise or, equivalently, the upper triangular component is stored row-wise
* `kSquare`: The whole Hessian ``Q`` is stored column-wise. This is for input only: internally the Hessian is stored in `kTriangular` format
## SolutionStatus
This defines the nature of any primal or dual solution information:
* `kSolutionStatusNone`: There is no solution information
* `kSolutionStatusInfeasible`: The solution is not feasible
* `kSolutionStatusFeasible`: The solution is feasible
## BasisValidity
This defines the nature of any basis information:
* `kBasisValidityInvalid`: There is no basisn information
* `kBasisValidityValid`: The basis information is valid
## HighsModelStatus
This defines the status of the model after a call to `run`
* `kNotset`: The model status has not been set
* `kModelError`: There is an error in the model
* `kSolveError`: There has been an error when solving the model
* `kModelEmpty`: The model is empty
* `kOptimal`: The model has been solved to optimality
* `kInfeasible`: The model is infeasible
* `kUnboundedOrInfeasible`: The model is unbounded or infeasible
* `kUnbounded`: The model is unbounded
* `kObjectiveBound`: The bound on the model objective value has been reached
* `kObjectiveTarget`: The target value for the model objective has been reached
* `kTimeLimit`: The run time limit has been reached
* `kIterationLimit`: The iteration limit has been reached
* `kSolutionLimit`: The MIP solver has reached the limit on the number of LPs solved
* `kInterrupt`: The solver has been interrupted by the user
* `kMemoryLimit`: The solver has been unable to allocate sufficient memory
* `kUnknown`: The model status is unknown
## HighsBasisStatus
This defines the status of a variable (or slack variable for a constraint) in a
basis:
* `kLower`: The variable is nonbasic at its lower bound (or fixed value)
* `kBasic`: The variable is basic
* `kUpper`: The variable is at its upper bound
* `kZero`: A free variable is nonbasic and set to zero
* `kNonbasic`: The variable is nonbasic
## HighsOptionType
This defines the types of option values that control HiGHS:
* `kBool`: The option type is boolean
* `kInt`: The option type is integer
* `kDouble`: The option type is double
* `kString`: The option type is string
## HighsInfoType
This defines the types of (scalar) information available after a call to `run`:
* `kInt64`: The information type is 64-bit integer
* `kInt`: The information type is integer
* `kDouble`: The information type is double