QUEUE(FIFO) C CODE

//DATA STRUCTURE
//TOPIC:MENUDRIVEN QUEUE IMPLEMENTATION
//AUTHOR:DARSHIT VORA
#include < stdio.h >
#include < conio.h >
#include < process.h >
void insert();
void qdelete();
void display();
int f=-1,r=-1,i,ch,ele;
char ans;
int q[10];
void main()
{
clrscr();
do
{
clrscr();
printf("1 - insert");
printf("\n2 - delete");
printf("\n3 - display");
printf("\n4 - exit");
printf("\nWhat do u wanna do");
scanf("%d",&ch);
switch(ch)
{
case 1:
{
insert();
break;
}
case 2:
{
qdelete();
break;
}
case 3:
{
display();
break;
}
case 4:exit(0);
}
flushall();
printf("\nDo u wanna continue(y\n)");
flushall();
scanf("%d",&ans);
}while(ans=='y'||'Y');
getch();
}
void insert()
{
if(r==10)
{
printf("Queue is full");
}
if(r==-1 && f==-1)
{
printf("Queue is empty");
f=f+1;
r=r+1;
printf("Enter the element");
scanf("%d",&q[r]);
}
else
{
r=r+1;
printf("Enter the element");
scanf("%d",&q[r]);
}
}
void qdelete()
{
printf("%d is deleted",q[f]);
q[f]=NULL;
f=f+1;
if(r==-1 && f==-1)
{
printf("Queue is empty");
}
}
void display()
{
if(r==-1 && f==-1)
{
printf("Queue is empty");
}
else
{
for(i=f;i<=r;i++)
{
printf("\n%d",q[i]);
}
}

}