How to do operation on form submit,delete,update?

In any custom module file you have write an hook_nodeapi to do this "hook" is your module name

function hook_nodeapi(&$node, $op, $a3 = NULL, $a4 = NULL) {
switch ($op) {
case 'presave':
break;
case 'insert':
case 'update':
case 'view':
case 'delete':
}
}