C Program for Simple DSC order Priority QUEUE Implementation

#define SIZE 5            /* Size of Queue */
int PQ[SIZE],f=0,r=-1;       /* Global declarations */
 
PQinsert(int elem)
{
int i;       /* Function for Insert operation */
if( Qfull()) printf("\n\n Overflow!!!!\n\n");
else
{
i=r;
++r;
while(PQ[i] <= elem && i >= 0) /* Find location for new elem */
{
PQ[i+1]=PQ[i];
i--;
}
PQ[i+1]=elem;
}
}
 
int PQdelete()
{                      /* Function for Delete operation */
int elem;
if(Qempty()){ printf("\n\nUnderflow!!!!\n\n");
return(-1); }
else
{
elem=PQ[f];
f=f+1;
return(elem);
}
}
 
int Qfull()
{                     /* Function to Check Queue Full */
if(r==SIZE-1) return 1;
return 0;
}
 
int Qempty()
{                    /* Function to Check Queue Empty */
if(f > r) return 1;
return 0;
}
 
display()
{                  /* Function to display status of Queue */
int i;
if(Qempty()) printf(" \n Empty Queue\n");
else
{
printf("Front->");
for(i=f;i<=r;i++)
printf("%d ",PQ[i]);
printf("<-Rear");
}
}
 
main()
{                         /* Main Program */
int opn,elem;
do
{
clrscr();
printf("\n ### Priority Queue Operations(DSC order) ### \n\n");
printf("\n Press 1-Insert, 2-Delete,3-Display,4-Exit\n");
printf("\n Your option ? ");
scanf("%d",&opn);
switch(opn)
{
case 1: printf("\n\nRead the element to be Inserted ?");
scanf("%d",&elem);
PQinsert(elem); break;
case 2: elem=PQdelete();
if( elem != -1)
printf("\n\nDeleted Element is %d \n",elem);
break;
case 3: printf("\n\nStatus of Queue\n\n");
display(); break;
case 4: printf("\n\n Terminating \n\n"); break;
default: printf("\n\nInvalid Option !!! Try Again !! \n\n");
break;
}
printf("\n\n\n\n  Press a Key to Continue . . . ");
getch();
}while(opn != 4);
}