c - Implementing a binary search tree -

i'm trying implement binary search tree holds inventory of ordered stock. stocked item attributes stored in nodes such:

typedef struct item item_t; struct item{     char name;     int price;     int quantity;     item_t *left;     item_t *right; }; 

the idea prompt user enter above attributes, , add entered item node. i've written far:

item_t *root = null; item_t *current_leaf = null;  void prompt_user(){     /*     in here contains code prompts user item attributes     , stores in variable called input     */     insert_node(input); }  void insert_node(char *input){     /*if tree doesnt have root...*/     if (root == null){          /*create one...*/         *root = create_node(input);     }      else{         item_t *cursor = root;         item_t *prev = null;         int is_left = 0;         int comparison;          while(cursor != null){              /*comparison 1 key of input less key                of cursor, , 2 otherwise...*/             comparison = compare(input, cursor);             prev = cursor;              if(comparison == 1){                 is_left = 1;                 cursor = cursor->left;             }             else if (comparison == 2){                 is_left = 0;                 cursor = cursor->right;             }         }          if(is_left){             *prev->left = create_node(input);             current_leaf = prev->left;         }         else{             *prev->right = create_node(input);             current_leaf = prev->right;         }     } }  item_t create_node(char *input){      item_t *new_node = (item_t*)malloc(sizeof(item_t));      if (new_node == null){         printf("out of memory. shutting down.\n");         exit(exit_failure);     }      /*add data node...*/     update_item(input, new_node);      new_node->left = null;     new_node->right = null;      current_leaf = new_node;      return *new_node; } 

i want root pointing first item ever entered, , current_leaf pointing last item processed. compare returns 1 if item being processed (input) less last processed item (current_leaf). update_item sets data new nodes (leaves).

the above isn't complete, it's i'm @ moment. i'm struggling work out how write add_node , how keep current_leaf updated correctly.

edit: revised code

it example of bst. structure of tree is:

typedef struct node{     int data;     struct node *left, *right; }node; 

letting root global not idea, better declare inside main() , insert() called main this:

int main() {     int n,data;     node *root=null;     printf("how many elements? ");     scanf("%d",&n);     for(i=0;i<n;i++)     {          scanf("%d",&data);          insert(&root,data);     }     inorder(root);     return 0; } 

this code insertion , traversing binary tree-

void insert(node **root, int data) {     node *n1,*temp;     n1=(node *)malloc(sizeof(node));      n1->data=data;     n1->left=n1->right=null;     if(!(*root))     {         (*root)=n1;         //printf("node inserted\n");         return;     }     temp=*root;     while(temp!=null)     {         if(temp->data<temp->data)         {             //printf("to right");             if(temp->right==null)             {                 temp->right=n1;                 break;             }             else                 temp=temp->right;         }         else if(temp->data>=n1->data)         {             if(temp->left==null)             {                 temp->left=n1;                 break;             }             else                 temp=temp->left;         }     }     //printf("inserted\n"); }  void inorder(node *root) {     if(root==null)         return;     inorder(root->left);     printf("item: %d",root->data);     inorder(root->right); } 

the searching same same logic insert, please develop yourself.