1. Programming Languages and Paradigms
Activations
The figures in these slides are taken from the Sethi Textbook

2. Activation Records Revisited
Activation record (or frame): contains the data needed for the activation of a routine
Layout conventions depend on the language
Nested calls
Recursion
6/15/2005
Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved.

3. Activation Records in C
6/15/2005
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4. Activation Records in Pascal
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5. Nested Calls Suppose the functions main and f are defined as follows:
void main() { f(); g(); }
void f() { g(); }
There are two different activations of g() when the program executes g f
main g
main
6/15/2005
Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved.

6. Recursion Activation records using runtime stacks support recursion
Recursive calls create separate activations of the function
Example: binary search
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7. 6/15/2005
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8. 6/15/2005
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9. Links in Activation Records
Control links provide access to calling frames
Used to restore to calling frame when the called routine completes
Access links provide access to non-local data
In the next example, take note of the data that the procedures need access to
6/15/2005
Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved.

10. 6/15/2005
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11. 6/15/2005
Copyright 2005, by the authors of these slides, and Ateneo de Manila University. All rights reserved.