Control table

A control table is a table data structure (i.e. array of records) used to direct the control flow of a computer program. Software that uses a control table is said to be table-driven. A control table encodes both the parameters to a conditional expression and a function reference. An interpreter processes a table by evaluating the conditional expression for input data and invoking the selected function. Using a control table can reduce the need for repetitive code that implements the same logic.

In general, the mapping of input parameters can be via any data structure. A common data structure is the lookup, which provides relatively high performance but at a relatively high memory footprint. An associative array can minimize memory use at the cost of more lookup time.

How the associated behavior is referenced varies. Some languages provide a direct function reference (i.e. pointer) that can be used to invoke a function directly, but some languages do not. Some languages provide for jumping to a location (i.e.label). As a fallback, any language allows for mapping input to an index that can then be used to branch to a particular part of the code.

A control table is often used as part of a higher-level algorithm. It can control the main loop of an event-driven program. A relatively advanced use is instructions for a virtual machine – similar to bytecode but usually with operations implied by the table structure itself instead of encoded in the table data.