Source Code : Program that implements circular queue as an array.

_{/* CH7PR5.C: Program that implements circular queue as an array. */}

_{#include <stdio.h>}

_{#include <conio.h>}

_{#define MAX 10}

_{void addq ( int *, int, int *, int * ) ;}

_{int delq ( int *, int *, int * ) ;}

_{void display ( int * ) ;}

_{void main( )}

_{

  _{int arr[MAX] ;}

  _{int i, front, rear ;}

  _{clrscr( ) ;}

  _{/* initialise data member */}

  _{front = rear = -1 ;}

  _{for ( i = 0 ; i < MAX ; i++ )}

  _{arr[i] = 0 ;}

  _{addq ( arr, 14, &front, &rear ) ;}

  _{addq ( arr, 22, &front, &rear ) ;}

  _{addq ( arr, 13, &front, &rear ) ;}

  _{addq ( arr, -6, &front, &rear ) ;}

  _{addq ( arr, 25, &front, &rear ) ;}

  _{printf ( "\nElements in the circular queue: " ) ;}

  _{display ( arr ) ;}

  _{i = delq ( arr, &front, &rear ) ;}

  _{printf ( "Item deleted: %d", i ) ;}

  _{i = delq ( arr, &front, &rear ) ;}

  _{printf ( "\nItem deleted: %d", i ) ;}

  _{printf ( "\nElements in the circular queue after deletion: " ) ;}

  _{display ( arr ) ;}

  _{addq ( arr, 21, &front, &rear ) ;}

  _{addq ( arr, 17, &front, &rear ) ;}

  _{addq ( arr, 18, &front, &rear ) ;}

  _{addq ( arr, 9, &front, &rear ) ;}

  _{addq ( arr, 20, &front, &rear ) ;}

  _{printf ( "Elements in the circular queue after addition: " ) ;}

  _{display ( arr ) ;}

  _{addq ( arr, 32, &front, &rear ) ;}

  _{printf ( "Elements in the circular queue after addition: " ) ;}

  _{display ( arr ) ;}

  _{getch( ) ;}

_}

_{/* adds an element to the queue */}

_{void addq ( int *arr, int item, int *pfront, int *prear )}

_{

  _{if ( ( *prear == MAX - 1 && *pfront == 0 ) || (  *prear + 1 == *pfront ) )}

  _{

  _{printf ( "\nQueue is full." ) ;}

  _{return ;}

  _}

  _{if ( *prear == MAX - 1 )}

  _{*prear = 0 ;}

  _else

  _{( *prear )++ ;}

  _{arr[*prear] = item ;}

  _{if ( *pfront == -1 )}

  _{*pfront = 0 ;}

_}

_{/* removes an element from the queue */}

_{int delq ( int *arr, int *pfront, int *prear )}

_{

  _{int data ;}

  _{if ( *pfront == -1 )}

  _{

  _{printf ( "\nQueue is empty." ) ;}

  _{return NULL ;}

  _}

  _{data = arr[*pfront] ;}

  _{arr[*pfront] = 0 ;}

  _{if ( *pfront == *prear )}

  _{

  _{*pfront = -1 ;}

  _{*prear = -1 ;}

  _}

  _else

  _{

  _{if ( *pfront == MAX - 1 )}

  _{*pfront = 0 ;}

  _else

  _{( *pfront )++ ;}

  _}

  _{return data ;}

_}

_{/* displays element in a queue */}

_{void display ( int * arr )}

_{

  _{int i ;}

  _{printf ( "\n" ) ;}

  _{for ( i = 0 ; i < MAX ; i++ )}

  _{printf ( "%d\t", arr[i] ) ;}

  _{printf ( "\n" ) ;}

_}