The global data structures are composed of three arrays:

• comp_table (8x8): the component grid
• inst_table (8x64): the instance grid
• sig_table (8x64): the signal grid

The component grid is initialized at the top of the main() function with the components. After that, it is immutable.
The instance grid is updated by the circuit editor (at the bottom of main()) and used by compute_signals().
The signal grid is updated by compute_signals() once every cycle, and the two user output function (user_process_audio() and user_display_arrays() take the data from the top-right corner of this table.