dqueue.cpp

It is A c++ code to run a simulation

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
typedef struct queuenode
 {
 char data;
 struct queuenode* nextptr;
 }Queuenode;

typedef Queuenode*qptr;
void printqueue (qptr);
int isempty (qptr);
char dequeue (qptr*,qptr*);
void enqueue (qptr*,qptr*,char);
void instructions(void);
int main()
{clrscr();
 qptr headptr=NULL,tailptr=NULL;
 int choice;
 char item;
 instructions();
 printf ("?");
 scanf ("%d",&choice);
   while (choice!=3)
     {
      switch (choice)
	{
	 case 1:
	   {
	   printf ("Enter a character:");
	   scanf ("\n%c",&item);
	   enqueue (&headptr,&tailptr,item);
	   printqueue (headptr);
	   break;
	   }
	 case 2:
	   {
	    if (!isempty(headptr))
	     {
	       item=dequeue(&headptr,&tailptr);
	       printf ("%c has been dequeued.\n",item);
	     }
	    printqueue(headptr);
	    break;
	   }
	 default:
	  {
	   printf ("Invalid choice.\n\n");
	   instructions();
	   break;
	   }
      }
      printf ("?");
      scanf ("%d",&choice);
      }
     printf ("End of the Program");
     getch();
     return 0;
     }
 void instructions(void)
   {
    printf ("Enter your choice:\n");
    printf ("   1 to add an item to the queue\n");
    printf ("   2 to remove an item from the queue\n");
    printf ("   3 to end\n");
   }
 void enqueue (qptr *headptr,qptr*tailptr,char value)
   {
   qptr newptr;
   newptr= (Queuenode*)malloc(sizeof (Queuenode));
    if (newptr!=NULL)
      {
       newptr->data=value;
       newptr->nextptr=NULL;
	if (isempty(*headptr))
	     *headptr=newptr;
	else
	   (*tailptr)->nextptr=newptr;

       *tailptr=newptr;
      }
    else
      printf ("%c not inserted. No memory availale\n");
    }
   char dequeue (qptr *headptr,qptr*tailptr)
     {
     char value;
     qptr tempPtr;
     value =(*headptr)->data;
     tempPtr=*headptr;
     *headptr=(*headptr)->nextptr;
     if (*headptr==NULL)
       *tailptr=NULL;

       free (tempPtr);
       return value;
     }
   int isempty (qptr headptr)
      {
      return headptr==NULL;
      }
   void printqueue (qptr currentptr)
    {
    if (currentptr==NULL)
      {
       printf ("Queue is empty");
      }
    else
      {
	printf ("The Queue is:\n");

	while (currentptr!=NULL)
	  {
	   printf ("%c-->",currentptr->data);
	   currentptr=currentptr->nextptr;
	  }
      printf ("NULL\n\n");
      }
   }