Integer Pointers

#include <stdio.h>

int main(){
  int *p;                       /* declare a pointer to an integer */
  int i;

  p=(int *)malloc(sizeof(int)); /* Allocate a block of memory the size of an
                                   integer and make p point to that block */

  *p=4;                         /* Store 4 in that block */
  printf("*p+1 = %d\n", (*p)+1);

  free(p);                      /* free the memory allocated to p */

  /* Warning: If you don't free memory after you are done using the space,
     you will eventually use up all the memory available to your program. */

  p=(int *)malloc(7*sizeof(int)); /* Allocate a block 7 times the size of an
                                     integer. The pointer p points to the
                                     first integer in that block. */

  for (i=0; i<7; i++)
    p[i]=2*i+1;        /* Store 2*i+1 in the (i-1)th space in the block */

  for (i=0; i<7; i++)
    printf("p[%d]=%d ",i,p[i]);   /* Print the array. */
  printf("\n");

  /* There are two equivalent ways to access each element
     p[i] = *(p+i) */

  for (i=0; i<7; i++)
    printf("*(p+%d)=%d ",i,*(p+i));   /* Print the array. */
  printf("\n");

  p=(int *)realloc(p,9*sizeof(int));  /* Enlarge the array p points to. */

  p[7]=7;
  p[8]=8;

  for (i=0; i<9; i++)
    printf("p[%d]=%d ",i,p[i]);   /* Print the array. */
  printf("\n");

  free(p);             /* Again it is really bad to forget this */

  return 0;
}