FCFS Disk Scheduling Algorithm

#include<stdio.h>
#include<conio.h>
#include<math.h>
#define max 20
#define cymax 199

int i,req,ttl_tracks=0,cposn;
int cyposn[max];

void input()
{
 do
 {
  clreol();
  printf("\n Enter the current header position : ");
  scanf("%d",&cposn);
 }while(cposn>cymax || cposn <=0);
 printf("\n Enter the %d I/O Requests : ",req);
 cyposn[0] = cposn;
 for(i=1;i<=req;i++)
  scanf("%d",&cyposn[i]);
}

void FCFS()
{
 printf("\nS.No.  Current Position    Next Position   Displacement \n");
 printf("---------------------------------------------------------- \n\n");
 for(i=0;i<req;i++)
 {
  printf(" %d\t\t%d\t\t%d\t\t%d\n",i+1,cyposn[i],cyposn[i+1],abs(cyposn[i]-cyposn[i+1]));
  ttl_tracks += (abs(cyposn[i]-cyposn[i+1]));
 }
 printf("---------------------------------------------------------- \n\n");
 printf(" Total Tracks Displaced : %d",ttl_tracks);
}

void main()
{
 do
 {
  clrscr();
  printf("\n Enter the number of requests : ");
  scanf("%d",&req);
 }while(req>max || req <=0);
 input();
 FCFS();
 getch();
}