The below example shows the concept of FIFO. The First Inserted Element is shown at first position and if you want to retrieve the element then first inserted element will be retrieved first.

#include<stdio.h>
#include<conio.h>
#include<process.h>
void insert();
void retrive();
void disp();

int arr[5];
int top=0,last=-1;

void main()
{
int ch;
clrscr();
    while(1)
    {
        printf("\n1:Insert");
        printf("\n2:Retrive");
        printf("\n3:Display");
        printf("\n4:Exit");
        printf("\n\tPlease Enter Your Choice:-");
        scanf("%d",&ch);

        switch(ch)
        {
            case 1:
            insert();
            break;

            case 2:
            retrive();
            break;

            case 3:
            disp();
            break;

            case 4:
            exit(1);

            default:
            printf("\n\tYou Have Entered Wrong Choice");
            break;
        }
    }
getch();
}

void insert()
{
last++;

    if(last==5)
    {
        printf("\n\tQueue is Overflow Stop Inserting Element");
        last--;
    }
    else
    {

        printf("\n\tEnter the Element:=");
        scanf("%d",&arr[last]);
    }
}

void retrive()
{

    if(last<top)
    {
        printf("\n\tQueue is Empty No Element to Retrive");
    }
    else
    {
        printf("\n\t %d is Retrive",arr[top]);
        top++;
    }

}

void disp()
{
int ele=top;
    if(top>last)
    {
          printf("\n\tQueue is Empty No Element Please Insert Element");
    }
    else
    {

        while(ele<=last)
        {
            printf("\n\t%d",arr[ele]);
            ele++;
        }
    }
}