C PROGRAM FOR NON RECURSIVE PREORDER TRAVERSAL

#include<stdio.h>
#include<stdlib.h>
struct Tnode{
struct Tnode*pleft;
struct Tnode*pright;char ch;
};
struct Tnode *stack[50];
int top;
void push(struct Tnode* ch1);
struct Tnode* pop();
struct Tnode*root;
struct Tnode*create_node(char c);
void create();
void insert(char c);
void print();
//main function
int main(){
top=-1;root=NULL;
create();
printf("\n");
print();
return 0;}

struct Tnode*create_node(char c){
struct Tnode*pnew=(struct Tnode*)malloc(sizeof(struct Tnode));
if(pnew){
pnew->ch=c;
pnew->pleft=NULL;
pnew->pright=NULL;}
return pnew;}
void insert(char c){
struct Tnode *pnew,*ptrav,*pa;
pnew=create_node(c);
if(!pnew) printf("no memeory\n");
else{
if(!root)
root=pnew;
else{
pa=root;ptrav=root;
while(ptrav){
pa=ptrav;
if(c<(ptrav->ch)){
ptrav=ptrav->pleft;}
else{
ptrav=ptrav->pright;}}
if(c<(pa->ch)){
pa->pleft=pnew;}
else{
pa->pright=pnew;}}return;}}
void create(){
char k,f;
int i,n;
printf("enter number of characters\n");scanf("%d",&n);
for(i=0;i<n;i++) {
scanf("%c",&f);
scanf("%c",&k);
insert(k);
}}
void push(struct Tnode *ch1){
top++;
stack[top]=ch1;
return;
}
struct Tnode *pop(){
struct Tnode* k;
if(top<0){
k=NULL;return k ;}
else
{

k=stack[top];
top--;
return k;
}
}
void print(){
char l;
int done=0;
struct Tnode *ptemp=NULL,*ptr=root;
push(ptr);
if(!root){printf("empty tree\n");
}else{
printf("NON Recursive:\n");
while(top>=0){
// ptemp=ptr;
          ptr=pop();
printf("%c",ptr->ch);
 if((ptr->pright)!=NULL){
ptemp=ptr->pright;
// printf("%c",ptr->ch);
push(ptemp);}
if((ptr->pleft)!=NULL){
ptemp=ptr->pleft;
// printf("%c",ptr->ch);
push(ptemp);
}
}
}}