# fsVarsIVarSet The **fsVarsIVarSet** function can be used to set the value of a specific `IVar`.   ##### Syntax ``` wasm FsVarError fsVarsIVarSet( FsOVarId iVarId, FsUnitId unitId, double value, FsObjectId target ); ```   ##### Parameters
ParametersDescription
iVarId

The ID of an IVar (found using fsVarsGetIVarId or fsVarsRegisterIVar).

unitIdThe ID of a unit (found using fsVarsGetUnitId).
valueThe new value of the variable.
target

The ID of the object on which the variable is being set.

  ##### Return Values The function returns `FsVarError`, where 0 means there is no error.   ##### Example ``` wasm FsUnitId unitId = fsVarsGetUnitId("DEGREES"); FsIVarId iVarId = fsVarsRegisterIVar("Toto", "LIGHTING"); double value = 8; if (fsVarsIVarSet(iVarId, unitId, value) == FS_VAR_ERROR_NONE) { // valid } else { // error } ```