Pointer Types and Arrays

Referencing and dereferencing

Examine the following example and predict its output. Also visualize on a memory band what gets done after each initialization or assignment:

session03/vars.c

#include <stdio.h>

int main()
{
    double  x   = 1.23;
    double  y   = 2.13;
    double  *p  = &x;
    double  **q = &p;

    printf("x = %10.4lf\ny = %10.4lf\n\n", x, y);

    *p = 6.66;

    printf("x = %10.4lf\ny = %10.4lf\n\n", x, y);

    **q = 4.2;

    printf("x = %10.4lf\ny = %10.4lf\n\n", x, y);

    *q = &y;
    *p = 6.66;

    printf("x = %10.4lf\ny = %10.4lf\n\n", x, y);

    **q = 4.2;
    printf("x = %10.4lf\ny = %10.4lf\n\n", x, y);
}

Arrays

Complete the following code snippet such that:

function init initializes an array of length \(n\) with values \(1, \dots, n\).
function sum returns the sume of the elements.

Use the * and bracket notation for accessing elements.

session03/array_assign.c

#include <stddef.h>
#include <stdio.h>

#define N 6

double some_array[N];

void init(size_t n, double *x)
{
    // your code
}

double sum(size_t n, const double *x)
{
    double res = 0;

    // your code

    return res;
}

int main()
{
    init(N, some_array);
    printf("res = %10.3lf\n", sum(N, some_array));

    return 0;
}