Priority Queue Implementation using Linked List

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

//Data Structure Declaration
struct Element
{
 int value;
 int priority;
 struct Element *next;
};

struct Element *FRONT=NULL,*REAR=NULL,*temp=NULL,*head=NULL; 


int SIZE=5,COUNT=0;

//Function Declaration
void enqueue(int,int);
void dequeue();
void displayQueue();
int countElement();

//Main Function
int main()
{
 int choice,priority,value;
 //You are free to create more variable, if needed
 do
 {
  system("cls"); // To clear the screen
  printMenu();
  printf("\nEnter Your Choice : ");
  scanf("%d",&choice);
  
  switch(choice)
  {
   case 1:
    if(COUNT<SIZE)
    {
    printf("\n Enter Value for Element : ");
    scanf("%d",&value);
    printf("\n Enter Priority for Element : ");
    scanf("%d",&priority);
    enqueue(value,priority);
COUNT++; 
}
else
{
printf("\n Queue is Overflow");
}
        
    break;
    
   case 2:
    if(COUNT>0)
    {
    dequeue();
COUNT--; 
}
else
{
printf("\n Queue is Underflow");
}
    break;
    
   case 3:
    if(COUNT>0)
    {
    displayQueue();
}
else
{
printf("\n Queue is Empty");
}
   
    break;
    
   case 4:
    printf("\n No of Element in Queue : %d",countElement());
    break;
    
  
   default:
    printf("Thanks for Using Queue Program");
  }
  
  getch(); //To stop output on Screen
  
 }while(choice>0 && choice<5);
 return 0;
}


//Function Implementation
void printMenu()
{
 printf("\n==============================");
 printf("\nPRIORITY QUEUE OPERATION MENU");
 printf("\n==============================");
 printf("\n     1 - ENQUEUE");
 printf("\n     2 - DEQUEUE");
 printf("\n     3 - DISPLAY");
 printf("\n     4 - SIZE");
 printf("\n     5 - EXIT");
 printf("\n==============================");
}

void enqueue(int value,int priority)
{
temp=(struct Element *)malloc(sizeof(struct Element)*1);
temp->value=value;
temp->priority=priority;
temp->next=NULL;
printf("\n IN Function");

if(FRONT==NULL)
{
FRONT=temp;
REAR =temp;
printf("\n IN NULL");
}
else if(FRONT->next==NULL)
{
if(temp->priority > FRONT->priority)
{
temp->next=FRONT;
FRONT=temp;
}
else
{
REAR->next=temp;
REAR=temp;
}
}
else
{
head=FRONT;
if(temp->priority > head->priority)
{
temp->next=FRONT;
FRONT=temp;
}
else
{
while(temp->priority <= (head->next)->priority)
{
head=head->next;
if(head->next==NULL)
{
break;
}
}

if(head->next==NULL)
{
REAR->next=temp;
REAR=temp;
}
else if(temp->priority > (head->next)->priority)
{
temp->next=head->next;
head->next=temp;
}
}
}
}

void dequeue()
{
temp=FRONT;
FRONT=FRONT->next;
free(temp);
}


void displayQueue()
{
head=FRONT;
while(head!=NULL)
{
printf(" |%d|%d| -> ",head->value,head->priority);
head=head->next;
}
}

int countElement()
{
return COUNT;
}