The part in which i am stuck in this program is that....say consider in the function printPreorder what happens when when node==NULL.....where does the control flow...all in all if i am able to understand any of the traversal function code be it preorder or any...it could solve my problem.Please help.Code:#include <stdio.h> #include <stdlib.h> /* A binary tree node has data, pointer to left child and a pointer to right child */ struct node { int data; struct node* left; struct node* right; }; /* Helper function that allocates a new node with the given data and NULL left and right pointers. */ struct node* newNode(int data) { struct node* node = (struct node*) malloc(sizeof(struct node)); node->data = data; node->left = NULL; node->right = NULL; return(node); } /* Given a binary tree, print its nodes according to the "bottom-up" postorder traversal. */ void printPostorder(struct node* node) { if (node == NULL) return; // first recur on left subtree printPostorder(node->left); // then recur on right subtree printPostorder(node->right); // now deal with the node printf("%d ", node->data); } /* Given a binary tree, print its nodes in inorder*/ void printInorder(struct node* node) { if (node == NULL) return; /* first recur on left child */ printInorder(node->left); /* then print the data of node */ printf("%d ", node->data); /* now recur on right child */ printInorder(node->right); } /* Given a binary tree, print its nodes in inorder*/ void printPreorder(struct node* node) { if (node == NULL) return; /* first print data of node */ printf("%d ", node->data); /* then recur on left sutree */ printPreorder(node->left); /* now recur on right subtree */ printPreorder(node->right); } /* Driver program to test above functions*/ int main() { struct node *root = newNode(1); root->left = newNode(2); root->right = newNode(3); root->left->left = newNode(4); root->left->right = newNode(5); printf("\n Preorder traversal of binary tree is \n"); printPreorder(root); printf("\n Inorder traversal of binary tree is \n"); printInorder(root); printf("\n Postorder traversal of binary tree is \n"); printPostorder(root); getchar(); return 0; }