A parameter is a user-settable filter on the data retrieved by the [[Invantive Control for Excel/Concepts/Block|blocks]] of a model. By setting parameter values, the model user restricts the downloaded data to a subset of the facts database, for instance a specific financial year, cost centre or company. Parameters are defined by the modeler and referenced in the filter and where clauses of blocks. Each parameter has: - a code (`prr_code`): the identifier used in block queries; - a description (`prr_description`): shown to the model user when asking for a value; - a sorting order, determining the display order in the parameter dialog; - a display flag: hidden parameters get their value from formulas or extensions instead of user input; - a mandatory flag: mandatory parameters must have a value before data can be downloaded; - a current value and a default value. When a model user opens a workbook or starts a [[Invantive Control for Excel/Concepts/Synchronization|synchronisation]] and mandatory parameters have no value yet, Invantive Control prompts for them. Parameter values can also be changed at any time through "Edit Parameters" on the Control ribbon (see [[Invantive Control for Excel/User Interface/Control Ribbon|Control Ribbon]]). The current value and description of a parameter can be retrieved in worksheet formulas with `I_PRR_VALUE` and `I_PRR_DESCRIPTION`, for instance to display the selected filter in a report header. See [[Invantive Control for Excel/Formulas/Formulas|Formulas]].