Nonvirtual and Virtual Blocks

Simulink^® blocks fall into two basic categories: nonvirtual blocks and virtual blocks.

Nonvirtual blocks play an active role in the simulation of a system. If you add or remove a nonvirtual block, you change the model behavior.
Virtual blocks help organize a model graphically. While they play no active role in the simulation, they can affect the execution order of other blocks.

Some Simulink blocks are virtual in some circumstances and nonvirtual in others. Such blocks are called conditionally virtual blocks.

The table lists Simulink virtual and conditionally virtual blocks.

Block Name	Condition Under Which Block Is Virtual
Bus Assignment	Virtual if input bus is virtual.
Bus Creator	Virtual if output bus is virtual.
Bus Selector	Virtual if input bus is virtual.
Demux	Always virtual.
Enable	Virtual unless connected directly to an Outport block.
From	Always virtual.
Goto	Always virtual.
Goto Tag Visibility	Always virtual.
Ground	Always virtual.
In Bus Element	Virtual unless input bus is nonvirtual and contains a variable-size signal.
Inport	Always virtual. (since R2022a) Before R2022a: Virtual unless* the block resides in a conditionally executed or atomic subsystem and has a direct connection to an Outport block.*
Mux	Always virtual.
Out Bus Element	Virtual unless output bus is nonvirtual.
Outport	Virtual when the block resides within any subsystem (conditional or not), and does not reside in the root (top-level) Simulink window. For more information, see Ensure outport is virtual.
Selector	Virtual only when Number of input dimensions specifies `1` and Index Option specifies `Select all`, `Index vector (dialog)`, or `Starting index (dialog)` for fixed-size index signal.
Signal Specification	Always virtual.
Subsystem	Virtual unless the block is conditionally executed or the Treat as atomic unit check box is selected. You can check if a block is virtual with the `IsSubsystemVirtual` block property. See Programmatically Specify Block Parameters and Properties.
Terminator	Always virtual.
Trigger	Virtual when the output port is not present.

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