Thread: Queues

>also suggest me ways for better/best identation technique?
There's not a "best" way to indent. What people complain about is your consistency. As long as you format your code in a consistent way, it doesn't matter much how it looks because people will be able to figure out your indention style and be able to read the code. Here's your code with a more consistent formatting:

Code:

#include<stdio.h>
#include<conio.h>
#include<process.h>
#define Q_SIZE 5
/*function declarations*/
int underflow(int,int);
int overflow(int);
void insert(int a[],int r);
void deleted(int a[],int f,int r);
void display(int a[],int f,int r);
/*variable declarations*/
int q1[Q_SIZE],q2[Q_SIZE],q3[Q_SIZE];
int f1=0,r1=-1,f2=0,r2=-1,f3=0,r3=-1;
void main()
{
  clrscr();
  int choice;
  int prio;
  for(;;)
  {
    printf("Que no.\n");
    scanf("%d",&prio);
    printf("ENTER 1 FOR INSERTION 2 FOR DELETION");
    printf("ENTER 3 FOR DISPLAY 4 FOR EXIT\n");
    printf("ENTER YOUR CHOICE\n");
    scanf("%d",&choice);
    switch(choice)
    {
    case 1:
      if(prio==1)
      {
        insert(q1, r1);
        break;
      }
      if(prio==2)
      {
        insert( q2, r2 ) ;
        break;
      }
      if(prio==3)
      {
        insert( q3, r3 );
        break;
      }
    case 2:
      if(prio==1)
      {
        deleted( q1, f1,r1 );
        break;
      }
      if(prio==2)
      {
        deleted( q2, f2,r1 ) ;
        break;
      }
      if(prio==3)
      {
        deleted( q3, f3,r1 );
        break;
      }
    case 3:
      if(prio==1)
      {
        display( q1,f1, r1 );
        break;
      }
      if(prio==2)
      {
        display( q2,f2,r2 );
        break;
      }
      if(prio==3)
      {
        display(q3,f3,r3);
        break;
      }
    default:
      exit(0);
    }
  }
}
/* overflow*/
int overflow(int r)
{
  if(r>Q_SIZE-1)
  {
    return 1;
  }
  else
  {
    return 0;
  }
}
/*underflow*/
int underflow(int f,int r)
{
  if(f>r)
  {
    return 1;
  }
  else
  {
    return 0;
  }
}
/*insert*/
void insert(int q[],int r)
{
  if(overflow(r)==1)
  {
    printf("overflow reached");
    return;
  }
  else
  {
    int item;
    printf("enter the item to be inserted");
    scanf("%d",&item);
    q[++r]=item;
    printf("%d",r1);/*confusion why is r1 =-1*/
  }
}
/* delete*/
void deleted(int q[],int f,int r)
{
  int item;
  if(underflow(f,r)==1)
  {
    printf("underflow reached");
    return;
  }
  else
  {
    item=(q[f++]);
    printf("deleted item is ..%d\n",item);
  }
}
/* display*/
void display(int a[],int f,int r)
{
  if(underflow(f,r)==1)
  {
    printf("underflow nothing to display\n");
    return;
  }
  else
  {
    printf("elments in queue are \n");
    for(int i=f;i<=r;i++)
      printf("%d\n",a[i]);
  }
}

Vertical whitespace is also a good thing. You can use it to separate blocks of code that are logically separated from other blocks. There are also ways to tighten up what you have. Here's my second pass on your code:

Code:

#include <stdio.h>
#include <stdlib.h>

#define Q_SIZE 5

/*function declarations*/
int underflow(int,int);
int overflow(int);
void insert(int a[],int r);
void deleted(int a[],int f,int r);
void display(int a[],int f,int r);

/*variable declarations*/
int q1[Q_SIZE],q2[Q_SIZE],q3[Q_SIZE];
int f1=0,r1=-1,f2=0,r2=-1,f3=0,r3=-1;

int main()
{
  int choice;
  int prio;

  for(;;)
  {
    printf("Que no.\n");
    scanf("%d",&prio);

    printf("ENTER 1 FOR INSERTION 2 FOR DELETION");
    printf("ENTER 3 FOR DISPLAY 4 FOR EXIT\n");
    printf("ENTER YOUR CHOICE\n");
    scanf("%d",&choice);

    switch(choice)
    {
    case 1:
      if(prio==1) insert(q1,r1);
      if(prio==2) insert(q2,r2);
      if(prio==3) insert(q3,r3);
      break;
    case 2:
      if(prio==1) deleted(q1,f1,r1);
      if(prio==2) deleted(q2,f2,r1);
      if(prio==3) deleted(q3,f3,r1);
      break;
    case 3:
      if(prio==1) display(q1,f1,r1);
      if(prio==2) display(q2,f2,r2);
      if(prio==3) display(q3,f3,r3);
      break;
    default: exit(0);
    }
  }

  return 0;
}

/* overflow*/
int overflow(int r)
{
  return r>Q_SIZE-1;
}

/*underflow*/
int underflow(int f,int r)
{
  return f>r;
}

/*insert*/
void insert(int q[],int r)
{
  if(overflow(r)==1)
  {
    printf("overflow reached");
  }
  else
  {
    int item;

    printf("enter the item to be inserted");
    scanf("%d",&item);

    q[++r]=item;
    printf("%d",r1);/*confusion why is r1 =-1*/
  }
}

/* delete*/
void deleted(int q[],int f,int r)
{
  if(underflow(f,r)==1)
  {
    printf("underflow reached");
  }
  else
  {
    int item;

    item=(q[f++]);
    printf("deleted item is ..%d\n",item);
  }
}

/* display*/
void display(int a[],int f,int r)
{
  if(underflow(f,r)==1)
  {
    printf("underflow nothing to display\n");
  }
  else
  {
    printf("elments in queue are \n");
    for(int i=f;i<=r;i++)
      printf("%d\n",a[i]);
  }
}

See the difference?