The original 1746-BAS and 1771-BAS modules had a system-on-chip version of the Intel 8052 microcontroller that ran the BASIC-52 language, with an API and calls that allowed it to interface with the backplane.
Modern Prosoft modules that do similar things have an Intel 80386 system-on-chip that runs DOS.
There aren't a lot of good reasons to run one of these modules in a modern control system, as most of the things they do can be done better on an HMI computer or a network-connected device.
But if you've got an application that calls for simple serial functions and some functions that are appropriate for BASIC, then go ahead.