#include <stdio.h>
#include <stdlib.h>

#define NRows 3
#define NCols 4

int main(int argc, char *argv[])
{
    int i, j;

    double* p;    // We uses this reference variable to access
                  // dynamically created array elements

    p = calloc(NRows*NCols, sizeof(double) );  // 3x4 = 12 elements

    for ( i = 0; i < NRows; i++ )
       for ( j = 0; j < NCols; j++ )
           p[i*NCols + j] = i+j;   // put value i+j in array element p[i][j]

    for ( i = 0; i < NRows; i++ )
    {
       for ( j = 0; j < NCols; j++ )
          printf("p[%d][%d] = %lf  ", i, j, p[i*NCols + j] );
       putchar('\n');
    }

    free(p);      // Un-reserve the first array
}