Implementation of Binary Tree Using Linked List

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


struct btreenode
{
struct btreenode *leftchild;
int data;
struct btreenode *rightchild;
};


insert(struct btreenode**,int);
inorder(struct btreenode*);
preorder(struct btreenode*);
postorder(struct btreenode*);

int main()
{
struct btreenode *bt;
int req, i=0, num;

bt=NULL;
clrscr();

printf("Specify the no of data to be entered::\n");
scanf("%d",&req);

while(i<req)
{
printf("Enter the ith i.e %d number::",i);
scanf("%d",&num);
insert(&bt , num);   //need to define later.....function call
i++;
}

clrscr();

printf("Inorder Traversal::\n");
inorder(bt);   //define later

printf("\n\nPreorder Traversal::\n");
preorder(bt);   //define later

printf("\n\n    Post order Traversal::\n");
postorder(bt);   //define later


getch();
 return 0;
}
        /*insert a node to an binary tree*/
        insert(struct btreenode **sr, int num)
        {
        if(*sr == NULL)
        {
        *sr = malloc(sizeof(struct btreenode));

        (*sr)->leftchild=NULL;
        (*sr)->data = num;
        (*sr)->rightchild = NULL;
        }

        else  /*search the node where to be add*/
        {
        /*if new data is less then traverse to left*/
        if(num<((*sr)->data))
        insert(&((*sr)->leftchild),num);
        else
        insert(&((*sr)->rightchild), num);

        }
        }

    /*traversing the node in inoreder fashion*/

    inorder(struct btreenode *sr)
    {

    if(sr!=NULL)
    {
    inorder(sr->leftchild);
    printf("%d    ",sr->data); //print the data that has already traversed
                //whose left child is null
    inorder(sr->rightchild);
    }
    else
    {}
    }


    preorder(struct btreenode *sr)
    {

    if(sr!=NULL)
    {
    printf("%d    ",sr->data); //print the data that has already traversed

    preorder(sr->leftchild);
                //whose left child is null
    preorder(sr->rightchild);
    }
    else
    {}
    }

    postorder(struct btreenode *sr)
    {

    if(sr!=NULL)
    {
    postorder(sr->leftchild);
    postorder(sr->rightchild);

    printf("%d    ",sr->data); //print the data that has already traversed
                //whose left child is null

    }
    else
    {}
    }