Queue using array

#include<iostream>
using namespace std;

int q[5];

int f=-1;
int r=-1;

void insert()
{
int item;
if((f==0 && r==4) || (r+1==f))
{
cout<<"overflow";
return;
}

if(f==-1)
{
f=0;r=0;
}
else if(r==4)
{
r=0;
}
else
r++;

cout<<"insert item:"<<endl;
cin>>item;
q[r]=item;
return;
}

void del()
{

if(f==-1)
{
cout<<"underflow"<<endl;
return;
}
else
cout<<q[f]<<" is deleted....."<<endl;

if(f==r)
{
f=-1;r=-1;
return;
}
else if(f==4)
{
f=0;
return;
}
else
{
f++;
return;
}

}

void show()
{
if(f==-1)
{
cout<<"underflow"<<endl;
return;
}

for(int i=f;i<=r;i++)
cout<< q[i] <<endl;
return;
}


int main()
{
int c;


while(1)
{
cout<<"choose your choice"<<endl;
cout<<"1. insert"<<endl;
cout<<"2. delete"<<endl;
cout<<"3. show "<<endl;

cin>>c;
switch(c)
{
case 1:
insert();
break;
case 2:
del();
break;
case 3:
show();
break;
}
}

return 0;
}