1. CSC 172 DATA STRUCTURES

2. POINTERS

3. POINTERS
int a, b;
a = 7;
b = 11;

4. POINTERS
int a, b;
a = 7;
b = 11; a 7 b 11

5. POINTERS
int a, b;
a = 7;
b = 11; a 7 b 11
x01b5
xf37a

6. int a, b;
a = 7;
b = 11;
&a ;
//the address of a a 7 b 11
x01b5
xf37a

7. int *p ;
//declaring a pointer p
x0427 a 7 b 11
x01b5
xf37a

8. int *p
p = &a ; p
x01b5
x0427 a 7 b 11
x01b5
xf37a

9. int *p p = &a ; int c = *p ; 7 x015b 7 11 c p x219b x0427 a b x01b5
xf37a

10. Function Calls
Call by value – you get a copy of the data

11. swap1 (x, y )
int x, y ; {
int temp ;
temp = x ;
x = y;
y = temp; }
swap2 (px, py )
int *px, *py;{
int temp ;
temp = *px ;
*px = *py;
*py = temp; }

12. COMPUTER MEMORY: A BIG ARRAY

13. ADDRESS
CONTENT
x[0] x0000
x[1] x0001
x[2] x0002
. . .
. . .

14. . . . x[1] = 5; . . . ADDRESS CONTENT x[0] x0000 x[1] x0001 5

15. . . . x[3] = x[1]; . . . ADDRESS CONTENT x[0] x0000 x[1] x0001 5

16. . . . x[4] = &(x[1]); . . . ADDRESS CONTENT x[0] x0000 x[1] x0001 5

17. . . . x[6] = *(x[4]); . . . ADDRESS CONTENT x[0] x0000 x[1] x0001 5

18. int x = 1;
int y = 2;
int *ip ;
int z[10];

19. . . . int x = 1; int y = 2; int *ip ; int z[10]; x0bc1 x0bc1 1 x0bc2 2

20. . . . int x = 1; int y = 2; int *ip ; int z[10]; x0bc1 x0bc1 1 x0bc2 1
ip = &x;
y = *ip;
. . .

21. . . . int x = 1; int y = 2; int *ip ; int z[10]; x0bc1 x0bc1 1 x0bc2
x0bc1
x0bc1 1
x0bc2
x0bc4
x0bc3
x0bc4
ip = &x;
y = *ip;
*ip = 0 ;
ip = &z[10];
. . .

22. Arrays are pointers

23. ARRAYS ARE POINTERS
int a[3], *p; a
x01b5 p
x01b6
xf37a
x01b7

24. ARRAYS ARE POINTERS int a[3], *p; p = &a[0]; a p x01b5 x01b5 x01b6
xf37a
x01b7

25. ARRAYS ARE POINTERS int a[3], *p; p = &a[0]; p = a; // same a p x01b5
xf37a
x01b7

26. ARRAYS ARE POINTERS a[0] = 13; *p = 13; 13 a p x01b5 x01b5 x01b6 xf37a

27. ARRAYS ARE POINTERS a[1] = 29; *(p+1) = 29; 13 29 a p x01b5 x01b5
xf37a
x01b7

28. ARRAYS ARE POINTERS a[2] = 31; *(p+2) = 31; 13 29 31 a p x01b5 x01b5
xf37a 31
x01b7

29. int k;
for(k=0;k<3;k++){
a[k] = k * k; }
for (k=0;k<3;k++)
*(p+k) = k * k ;