1. Pointers and dynamic memory

2. malloc, calloc, realloc, free
Allocate block of memory
malloc - void* malloc(size_t size) //unsigned int
calloc
realloc
free - deallocate block of memory
Memory (heap)
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3. malloc, calloc, realloc, free
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Allocate block of memory
malloc - void* malloc(size_t size) //unsigned int
void *p = malloc(4)
print p //200

4. malloc, calloc, realloc, free
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Allocate block of memory
malloc - void* malloc(size_t size) //unsigned int
int *p = (int*) malloc(3*sizeof(int))
print p //200
*p = 2
*(p+1) = 4
*(p+2) = 5

5. malloc, calloc, realloc, free
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Allocate block of memory
malloc - void* malloc(size_t size) //unsigned int
int *p = (int*) malloc(3*sizeof(int))
print p //200
p[0] = 2
p[1] = 4
p[2] = 5

6. malloc, calloc, realloc, free
Allocate block of memory
malloc - void* malloc(size_t size) //unsigned int
calloc - void* calloc(size_t num, size_t size)
int *p = (int*) calloc(3, sizeof(int))
Memory (heap)
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7. malloc, calloc, realloc, free
Allocate block of memory
malloc - void* malloc(size_t size) //unsigned int
calloc - void* calloc(size_t num, size_t size)
realloc - void* realloc(void *ptr, size_t size)
Memory (heap)
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8. #include<stdio. h> #include<stdlib
#include<stdio.h> #include<stdlib.h> int main() { int n, i; printf("Enter size of array\n"); scanf("%d",&n); int A[n]; for (i = 0; i < n; i++) A[i] = 1+i; printf("the value is %d\n", A[i]); }

9. malloc
#include<stdio.h> #include<stdlib.h> int main() { int n, i; printf("Enter size of array\n"); scanf("%d",&n); int *A = (int*) malloc(n*sizeof(int)); //dynamically allocated array for (i = 0; i < n; i++) A[i] = 1+i; printf("%d ", A[i]); }

10. calloc
#include<stdio.h> #include<stdlib.h> int main() { int n, i; printf("Enter size of array\n"); scanf("%d",&n); int *A = (int*) calloc(n,sizeof(int)); //dynamically allocated array for (i = 0; i < n; i++) A[i] = 1+i; printf("%d ", A[i]); }

11. calloc
#include<stdio.h> #include<stdlib.h> int main() { int n, i; printf("Enter size of array\n"); scanf("%d",&n); int *A = (int*) calloc(n,sizeof(int)); //dynamically allocated array for (i = 0; i < n; i++) printf("%d ", A[i]); }

12. free
#include<stdio.h> #include<stdlib.h> int main() { int n, i; printf("Enter size of array\n"); scanf("%d",&n); int *A = (int*) malloc(n*sizeof(int)); //dynamically allocated array for (i = 0; i < n; i++) A[i] = 1+i; free(A); printf("%d ", A[i]); }

13. free
#include<stdio.h> #include<stdlib.h> int main() { int n, i; printf("Enter size of array\n"); scanf("%d",&n); int *A = (int*) malloc(n*sizeof(int)); //dynamically allocated array for (i = 0; i < n; i++) A[i] = 1+i; //free(A); printf("%d ", A[i]); }

14. free
#include<stdio.h> #include<stdlib.h> int main() { int n, i; printf("Enter size of array\n"); scanf("%d",&n); int *A = (int*) malloc(n*sizeof(int)); //dynamically allocated array for (i = 0; i < n; i++) A[i] = 1+i; free(A); A[3] = 9; printf("%d ", A[i]); }

15. free
#include<stdio.h> #include<stdlib.h> int main() { int n, i; printf("Enter size of array\n"); scanf("%d",&n); int *A = (int*) malloc(n*sizeof(int)); //dynamically allocated array for (i = 0; i < n; i++) A[i] = 1+i; free(A); A = NULL; //Adjust pointer to NULL after free printf("%d ", A[i]); }

16. realloc
#include<stdio.h> #include<stdlib.h> int main() { int n, i; printf("Enter size of array\n"); scanf("%d",&n); int *A = (int*) malloc(n*sizeof(int)); //dynamically allocated array for (i = 0; i < n; i++) A[i] = 1+i; int *B = (int*) realloc(A, 2*n*sizeof(int)); printf("Previous block address = %p, new address = %p\n", A,B); for (i = 0; i < 2*n; i++) printf("%d\n", B[i]); }

17. realloc
#include<stdio.h> #include<stdlib.h> int main() { int n, i; printf("Enter size of array\n"); scanf("%d",&n); int *A = (int*) malloc(n*sizeof(int)); //dynamically allocated array for (i = 0; i < n; i++) A[i] = 1+i; int *B = (int*) realloc(A, 2*n*sizeof(int)); printf("Previous block address = %p, new address = %p\n", A,B); for (i = 0; i < 2*n; i++) printf("%d\n", B[i]); }

18. realloc
#include<stdio.h> #include<stdlib.h> int main() { int n, i; printf("Enter size of array\n"); scanf("%d",&n); int *A = (int*) malloc(n*sizeof(int)); //dynamically allocated array for (i = 0; i < n; i++) A[i] = 1+i; int *B = (int*) realloc(A, (n/2)*sizeof(int)); printf("Previous block address = %p, new address = %p\n", A,B); printf("%d\n", B[i]); }

19. realloc as free
#include<stdio.h> #include<stdlib.h> int main() { int n, i; printf("Enter size of array\n"); scanf("%d",&n); int *A = (int*) malloc(n*sizeof(int)); //dynamically allocated array for (i = 0; i < n; i++) A[i] = 1+i; int *B = (int*) realloc(A, 0); //equivalent to free(A) printf("Previous block address = %p, new address = %p\n", A,B); printf("%d\n", B[i]); }

20. realloc as malloc
#include<stdio.h> #include<stdlib.h> int main() { int n, i; printf("Enter size of array\n"); scanf("%d",&n); int *A = (int*) malloc(n*sizeof(int)); //dynamically allocated array for (i = 0; i < n; i++) A[i] = 1+i; int *B = (int*) realloc(NULL, n*sizeof(int)); //equivalent to malloc printf("Previous block address = %p, new address = %p\n", A,B); printf("%d\n", B[i]); }