# C Program for Circular QUEUE Operations – using Array

Source: Dr. G T Raju, Professor & Head, Dept. of CSE, RNSIT

```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 #define SIZE 5 /* Size of Circular Queue */ int CQ[SIZE],f=-1,r=-1; /* Global declarations */   CQinsert(int elem) { /* Function for Insert operation */ if( CQfull()) printf("\n\n Overflow!!!!\n\n"); else { if(f==-1)f=0; r=(r+1) % SIZE; CQ[r]=elem; } } int CQdelete() { /* Function for Delete operation */ int elem; if(CQempty()){ printf("\n\nUnderflow!!!!\n\n"); return(-1); } else { elem=CQ[f]; if(f==r){ f=-1; r=-1;} /* Q has only one element ? */ else f=(f+1) % SIZE; return(elem); } } int CQfull() { /* Function to Check Circular Queue Full */ if( (f==r+1) || (f == 0 && r== SIZE-1)) return 1; return 0; }   int CQempty() { /* Function to Check Circular Queue Empty */ if(f== -1) return 1; return 0; }   display() { /* Function to display status of Circular Queue */ int i; if(CQempty()) printf(" \n Empty Queue\n"); else { printf("Front[%d]->",f); for(i=f;i!=r;i=(i+1)%SIZE) printf("%d ",CQ[i]); printf("%d ",CQ[i]); printf("<-[%d]Rear",r); } }   main() { /* Main Program */ int opn,elem; do { clrscr(); printf("\n ### Circular Queue Operations ### \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); CQinsert(elem); break; case 2: elem=CQdelete(); if( elem != -1) printf("\n\nDeleted Element is %d \n",elem); break; case 3: printf("\n\nStatus of Circular 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); }```

### 8 Responses to “C Program for Circular QUEUE Operations – using Array”

1. Suramrit Singh

The only correct working example from many so called ‘programming’ websites.. ThanQ

2. rajarshi sen

i got a problem with the display function:
1. when there is only one element in the Queue, as in(f==r)..the loop wont run since(i=f; i!=r….)
2. this loop wont print the last element anyway, because the loop is meant to stop at i=r..hence not printing the last element (full or not)!
Pls help(:facing the same problem here:)
Thank You!

• rajarshi sen

solved::
for(i=front; ; i=(i+1)%max){
printf(” %d”, que[i]);
if(i==rear)break;
}
printf(” <-rear\n");

3. good solution explained in simplest way………

4. Can u make this for structures containing integer string and character instead of just one integer. I mean the array should contain the structures adressess and then can be retrieved and be replaced in queue