Queue

1:  #include<stdio.h>  
2:  #include<conio.h>  
3:  #define max 6  
4:  int i, x, front= -1, rear= -1, queue[max];  
5:  void add( );  
6:  void delet( );  
7:  void display( );  
8:  void main( )  
9:  {  
10:       int ch;  
11:       clrscr( );  
12:       while(1)  
13:  {  
14:       printf(“\n”);  
15:       printf(“\n 1. ADD”);  
16:       printf(“\n 2. DELETE”);  
17:       printf(“\n 3. DISPLAY”);  
18:       printf(“\n 4. EXIT”);  
19:       printf(“\n Enter your choice  : ”);  
20:       scanf(“%d”, &ch);  
21:       switch(ch)  
22:       {  
23:            case 1       :      add( );  
24:                          break;  
25:            case 2       :     delet( );  
26:                      break;  
27:            case 3   :     display( );  
28:                      break;  
29:            case 4   :      exit(1);  
30:            default  :   printf(“\n INVALID CHOICE”);  
31:       }  
32:  }  
33:  getch( );  
34:  }  
35:  void add( )  
36:  {  
37:       if(rear==max)  
38:            printf(“\nQUEUE OVERFLOWS”);  
39:       else  
40:       {  
41:            printf(“\nEnter the element to be inserted in queue : ”);  
42:            scanf(“%d” , &x);  
43:            rear++;  
44:            queue[rear]=x;  
45:       }  
46:  }  
47:  void delet( )  
48:  {  
49:       if(rear==front)  
50:            printf(“\nQUEUE UNDERFLOWS”);  
51:       else  
52:       {  
53:            front++;  
54:            x=queue[front];  
55:            printf(“\nDeleted element is %d”, x);  
56:       }  
57:  }  
58:  void display( )  
59:  {  
60:       int i;  
61:       if(front==rear)  
62:            printf(“\nQUEUE is EMPTY”);  
63:       else  
64:       {  
65:            printf(“\nQueue contains \n”);  
66:            for(i=front+1; i<=rear; i++)  
67:                 printf(“\t%d ”, queue[i]);  
68:       }  
69:  }