C Program to Print Queue

#include<stdio.h> 
 #include<process.h> 
 #define SIZE 5 
 int rear=-1; 
 int front=-1; 
 int a[SIZE]; 
 void main() 
 { 
         void insert(int); 
         int del(); 
         void display(); 
         int i,j,k; 
         char ch; 
         do 
          { 
                       clrscr(); 
                       printf("\n1.PUSH"); 
                       printf("\n2.POP"); 
                       printf("\n3.DISPLAY"); 
                       printf("\n4.EXIT"); 
                       printf("\nENTER YOUR CHOICE"); 
                       scanf("%d",&i); 
                       switch(i) 
                          { 
                             case 1:           printf("enter the item to be pushed"); 
                                                  scanf("%d",&j); 
                                                  insert(j); 
                                                  display(); 
                                                  break; 
                             case 2:           j=del(); 
                                                  printf("the item deleted is %d\n",j); 
                                                  display(); 
                                                  break; 
                             case 3:           display(); 
                                                  break; 
                             case 4:           exit(0); 
                                                  break; 
                                                  default:printf("\n any choice"); 
                          } 
                                                  fflush(stdin); 
                                                  printf("want to perform any more"); 
                                                  scanf("%c",&ch); 
            }while(ch=='y'); 
 } 
      void insert(int item) 
             { 
                  rear++; 
                  if(rear==0) 
                     { 
                            front=0; 
                     } 
                  else if(rear==SIZE) 
                          { 
                                  printf("queue full"); 
                                  rear--; 
                                  return; 
                           } 
                                  a[rear]=item; 
                                  return; 
               } 
       int del() 
              { 
                    int item ; 
                    if(front==-1) 
                      { 
                            printf("queue under flow"); 
                            return 0; 
                      } 
                    else if(rear==front) 
                           { 
                                  item=a[front]; 
                                  front=-1; 
                            } 
                          else 
                           { 
                                  item =a[front]; 
                            } 
                                  return item; 
               } 
                  void display() 
              { 
                    int i; 
                    for(i=front;i<=rear;i++) 
                        { 
                             printf("%d--",a[i]); 
                        } 
                             return; 
              }