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

int main ( ) {
    int     arr[10][20];    // a 2D array
    int     (*pa)[20];      // a pointer to a 2D array
    int     **b;            // a pointer to a pointer
    int     cols;

    // simple point at the given array
    pa = arr;

    // you can also call malloc to initialise
    // this synthesises arr[30][20]
    // the major size can be anything you want, but
    // the minor size is stuck at 20 at compile time
    pa = malloc ( 30 * sizeof(pa[0]) );

    // for total flexibility
    // this also allocates arr[30][20]
    // but you can choose all dimensions at run-time
    b = malloc( 30 * sizeof(b[0]) );
    for ( cols = 0 ; cols < 30 ; cols++ ) {
        b[cols] = malloc( 20 * sizeof(b[0][0]) );
    }

    return 0; 
}