1. A method, performed by a computer system, for providing a dispatch table that reflects an execution context of computer readable instructions, the method comprising: determining an execution context for computer readable instructions; responding to a change in the execution context by using the dispatch table which reflects the change; wherein the execution context for the instructions corresponds to the execution context of a thread executing in a data processing system, the thread being a real-time thread that is a schedulable object; wherein if the thread is a real-time thread, the execution context of the thread is one of: a real-time thread with no scope on a scope stack; a real-time thread with at least one scope on a scope stack; a no-heap real-time thread with no scope on a scope stack; or a no-heap real-time thread with at least one scope on the stack; wherein each execution context is associated with a corresponding dispatch table; and wherein determining a change in execution context includes: determining that the execution context of the thread has changed; and responding to the change by causing the thread to be associated with a dispatch table reflecting the change.