Write lines of code to do the following, in sequence:

1. Declare a variable x to be an int. int x;

2. Declare a variable p to be a pointer to int. int *p;

3. Set p to point to the variable x. p = &x;

4. Use the variable p (and NOT the variable x) to set the variable x equal to 47. *p = 47;

The following program will NOT swap (interchange) the values of a and b. Add and modify the code as necessary so that the program will do the swap.

#include <stdio.h>

void swap(int *i, int  *j) {
   int  t =  *i;
   *i =  *j;
   *j =  t;
}

int main() {
   int a = 23, b = 47;
   printf("Before. a: %d, b: %d\n", a, b);
   swap ( &a, &b  );
   printf("After.  a: %d, b: %d\n", a, b);
   return 0;
}

Consider the following program:

/* 1*/ #include <stdio.h>
/* 2*/
/* 3*/ int main() {
/* 4*/    int a[] = {4, 9, 25, 49, 121, 169, 289, 0};
/* 5*/    int i = 0;
/* 6*/    int sum = 0;
/* 7*/    while (a[i] != 0)
/* 8*/       sum = sum + a[i++];
/* 9*/    printf("Sum: %i\n", sum);
/*10*/ }

1. Rewrite the start of the while loop in line 7 so that it is shorter, but using the square bracket (array indexing) notation. while (a[i])

2. Rewrite lines 7 and 8 to use pointer notation (no use of square brackets).
   while (*(a + i) != 0)
   sum = sum + *(a + i++);