1. Call Stacks John Keyser

2. Stacks A very basic data structure. – Data structure: a container for holding data in a program. – Classes, structs can be thought of as data structures – The vector is a data structure we have already used. Like forming a stack of objects Two basic operations – Push (add something to top of stack) – Pop (remove whatever is on top of stack

3. Example: Push 5 Push 10 Pop Push 8 Push 1 Pop 5 5

4. Example: Push 5 Push 10 Pop Push 8 Push 1 Pop 5 10

5. Example: Push 5 Push 10 Pop Push 8 Push 1 Pop 5 10

6. Example: Push 5 Push 10 Pop Push 8 Push 1 Pop 5 8 8

7. Example: Push 5 Push 10 Pop Push 8 Push 1 Pop 5 8 1 1

8. Example: Push 5 Push 10 Pop Push 8 Push 1 Pop 5 108 1

9. Example: Push 5 Push 10 Pop Push 8 Push 1 Pop 5 8

10. Example: Push 5 Push 10 Pop Push 8 Push 1 Pop 5

11. Functions (aka routines, methods, etc.) When a function is called, it is pushed onto a call stack. – What is pushed on is a “function activation record” – This record contains the information/variables the function uses (effectively the local scope When a function finishes, it is popped off of the call stack. – It might return a value to the prior item in the stack. The call stack can get very deep – many functions are called from one another 11Stroustrup/Programming -- Oct'10

12. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …}

13. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A

14. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A B

15. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A B D

16. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A B

17. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A B E

18. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A B E G

19. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A B E

20. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A B

21. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A

22. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A C

23. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A C D

24. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A C

25. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A C F

26. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A C

27. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack A

28. Example 7 different functions (A through F) int A() {… B(); C(); …} int B() {… D(); E(); …} int C() {… D(); F(); …} int D() {…} int E() {… G(); …} int F() {…} int G() {…} main() {… A(); …} Call Stack