[ns] what does defining nodes initial position mean ?

[Karthik Talloju]

In the following code(it is not complete) :

$node_(0) set X_ 100.0
$node_(0) set Y_ 50.0
$node_(0) set Z_ 0.0

$node_(1) set X_ 300.0
$node_(1) set Y_ 50.0
$node_(1) set Z_ 0.0

# define mobiles initial position for nam
for {set i 0} {$i < $val(nn)} {incr i} {
     $ns_ initial_node_pos $node_($i) 50
}

what is the significance of 50 ? Why does nam need nodes' initial
position? We have specified the coordinates of node0 and node1
already. Can that information not be used by nam ?

Thanks for the help,
Karthik