gcb

The current block is:

• The most recently clicked block; when you select multiple blocks using a selection box, it is the first block that gets selected

• The S-Function block currently running its MATLAB^® function

• When a callback is invoked, the block invoking the callback; the current block can change during the execution of the callback, for example if you set breakpoints or interact with an editor.

• The block whose mask is being evaluated as part of the MaskInitialization parameter evaluation, provided the mask initialization code does not change the current block

• The last block loaded after opening a model

The current system is one of these:

• During editing, the most recently clicked subsystem or the subsystem that contains the most recently clicked block; if the most recent click is in the top level of the model hierarchy, the current system is the model.

• During simulation of a model that contains an S-Function block, the subsystem containing the S-Function block currently being evaluated; if the S-Function being evaluated is in the top level of the model hierarchy, the current system is the model.

• When a callback is invoked, the model, subsystem, or block invoking the callback; the current system can change during the execution of the callback, for example if you set breakpoints or interact with an editor.

• During evaluation of the MaskInitialization function, the subsystem containing the block whose mask is being evaluated; if the mask is in the top level of the model hierarchy, the current system is the model.

• The model most recently loaded into memory with the load_system function.

  If you load a model using the load_system function and then change the current system, loading the model a second time using the load_system function does not make the model the current system. To make the model the current system, close the model and then reload the model using the load_system function.