1. Introduction to Programming
Lecture 24

2. Today’s Agenda Memory Allocation Dynamic memory allocation
Advantages/disadvantages of Dynamic and static memory allocation
Common programming errors while using Dynamic memory allocation

3. Static Memory Allocation
int i , j , k ;
char s [ 20 ] ;

4. Compile Time Allocation

5. Dynamic Memory Allocation

6. Heap

7. Pointers

8. void Pointer

9. int *i ;
char *s ;
i is a pointer to an integer

10. void *ptr ;

11. Cast

12. void *ptr ;

13. ( int * ) ptr ;

14. NULL

15. calloc ( n , m ) ; Space in terms of numbers of elements
Space in terms of size each of elements

16. calloc ( 1000 , sizeof ( int ) ) ;

17. ( int * ) calloc ( 1000 , sizeof ( int ) ) ;

18. void * calloc ( size_t n , size_t el-size ) ;

19. Example 1
int *iPtr ;
iPtr = ( int * ) calloc ( 1000 , sizeof ( int ) ) ;
if ( iPtr == NULL )
exit ( ) ;

20. Number of bytes required
void * malloc ( n ) ;
Number of bytes required

21. malloc (1000 *sizeof ( int ) ) ) ;

22. malloc ( n ( sizeof ( float ) ) ) ;

23. Static Memory Allocation
#define MAXSTUDENT 100
int Student [ MAXSTUDENT ] ;

24. Problem statement
Find the average age of
the students in your class

25. Example 2 int numstd ; int *iPtr , *sPtr ;
cout << "Enter the number of students " << endl ;
cin >> numstd ;
iPtr = malloc ( numstd * ( sizeof ( int ) ) ) ;
if ( iPtr == NULL )
{         cout << "Error on malloc " ;         return 1 ;         /* Use a nonzero return to indicate an error has occurred */ }
// a while loop to read the ages of the student and place them in the memory
sPtr = iPtr ;
sPtr++ ;

26. free ( iPtr ) ;

27. realloc(void *iPtr, size_t size);

28. Unreferenced Memory

29. Memory Leaks

30. Example main ( ) { funct ( ) ; } funct ( ) int *iPtr ;
iPtr = malloc ( * ( sizeof ( int ) ) ) ;
// used the memory

31. Dangling Pointers

32. Example
int *ptr1 , *ptr2 ;
ptr1 = malloc (1000 * ( sizeof ( int ) ) ) ;
ptr2 = ptr1 ;
- - -
free ( ptr1 ) ;

33. Multi-tasking

34. Review Dynamic Memory Allocation Efficient usage of computers
resources
Have to do memory
management