C program inorder preorder postorder traversal

/* Data structure program to create a tree and traverse the tree in
1. preorder
2. inorder
3. postorder */

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

struct treelist
{
int data;
struct treelist *left;
struct treelist *right;
};
typedef struct treelist tree;

tree *cretree(tree *t,int data);
void preorder(tree *t);
void inorder(tree *t);
void postorder(tree *t);

void main()
{
tree *t = NULL;
int n,a,i,ch;
clrscr();
printf("How many numbers do you wan't to enter : ");
scanf("%d",&n);
for(i=0;i<n;i++)
{
printf("Enter number %d :....: ",i+1);
scanf("%d",&a);
t = cretree(t,a);
}
while(1)
{
printf("\nEnter the order of traversal of tree \n");
printf("1. preorder \n");
printf("2. inorder \n");
printf("3. postorder \n");
printf("4. Terminate the program\n");
printf("Enter the choice : ");
scanf("%d",&ch);
switch(ch)
{
case 1 :
preorder(t);
break;
case 2 :
inorder(t);
break;
case 3 :
postorder(t);
break;
case 4 :
printf("Good Bye");
getch();
exit(0);
default :
printf("You have entered wrong choice ");
break;
}
}
}

tree *cretree(tree *t,int x)
{
tree *newnode;
if(t == NULL )
{
newnode = (tree*)malloc(sizeof(tree));
newnode->data = x;
newnode->left = NULL;
newnode->right= NULL;
return(newnode);
}
else if(x < t->data)
{
if(t->left == NULL)
{
newnode = (tree*)malloc(sizeof(tree));
newnode->data = x;
t->left = newnode;
newnode->left = NULL;
newnode->right = NULL;
return(t);
}
else
cretree(t->left,x);
}
else
{
if(t->right == NULL)
{
newnode = (tree*)malloc(sizeof(tree));
newnode->data = x;
t->right = newnode;
newnode->left = NULL;
newnode->right = NULL;
return(t);
}
else
cretree(t->right,x);
}
return(t);
}
void preorder(tree *t)
{
if( t != NULL)
{
printf("Preorder : %d\n",t->data);
}
else
{
printf("Empty Tree");
return;
}
if(t->left != NULL)
preorder(t->left);
if(t->right != NULL)
preorder(t->right);
}


void inorder(tree *t)
{
if( t == NULL)
{
printf("Empty Tree");
return;
}
if(t->left != NULL)
inorder(t->left);

printf("Inorder : %d \n",t->data);

if(t->right != NULL)
inorder(t->right);
}

void postorder(tree *t)
{
if( t == NULL)
{
printf("Empty Tree");
return;
}
if(t->left != NULL)
postorder(t->left);


if(t->right != NULL)
postorder(t->right);

printf("Post Order : %d\n",t->data);
}