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# Runtime vs. Self-Installed Custom Operators

Although Self-Installed Custom Operators (SICOs) are the preferred way to implement custom operators in Softimage, legacy operators continue to be supported and you can also build operators on-the-fly, which are known as runtime operators.

Runtime operators are embedded directly within the scene. They are similar in implementation from SICOs but differ in a few key ways:

Area | Description | Runtime | SICO
--- | --- | --- | ---
Applying operators | To apply runtime operators, use either one of the AddScriptedOp methods or the AddScriptedOp command. For SICOs, you use the AddCustomOp versions. | AddScriptedOp Parameter.AddScriptedOp or Parameter::AddScriptedOp ProjectItem.AddScriptedOp or ProjectItem::AddScriptedOp | AddCustomOp Parameter.AddCustomOp or Parameter::AddCustomOp ProjectItem.AddCustomOp or ProjectItem::AddCustomOp
Update signature | Runtime operators include all output and input ports in the Update signature in addition to the context. SICOs only include the context in its Update signature. |
    Update(
    		ctxt,
    		outport,
    		inport1,
    		inport2,
    		...
    		)
    Update( ctxt )
Context available | The UpdateContext object is available for runtime operators. SICOs take the OperatorContext object instead. | UpdateContext or UpdateContext | OperatorContext or OperatorContext