Write a C program for R-Chart in statistics

How to Write a C program to generate R-Chart in statistics.

C program to generate R-Chart in statistics

#include<conio.h>
#include<stdio.h>
#include<math.h>
#include<stdlib.h>
#define D3 0
#define D4 2.115

void direct();
void indirect();

int num, r[50], i;
float r_m=0.0, R_m, ucl, lcl;


void main()
{
     int ch;
     clrscr();

     while(ch!=5)
     {
          printf("\nenter your choice ");
          printf("\npress 1 for direct mean of sampling range is given ");
          printf("\npress 2 for finding mean of sampling range ");
          printf("\npress 3 for exit ");
          printf("\n");
          scanf("%d",&ch);
          switch(ch)
          {
               case 1 :
                    direct();
                    break;

               case 2 :
                    indirect();
                    break;

               case 3 :
                    exit(0);
                    break;
               default :
                       printf("\nu enter wrong choice \n");
                       break;
          }
     }
getch();
}

void direct()
{
     printf("\n enter the value of mean of all given ranges i.e. R bar = ");
     scanf("%f",&R_m);
     ucl=D4*R_m;
     lcl=D3*R_m;
     printf("\nthe value of central line R_m =  %.3f",R_m);
     printf("\nthe value of upper control limit ucl =  %.3f",ucl);
     printf("\nthe value of lower control limit lcl =  %.3f\n",lcl);
}


void indirect()
{
     printf("\n enter the no of samples  = ");
     scanf("%d",&num);
     printf("\n enter the values of ranges  \n");
     for(i=0;i<num;i++)
     {
          scanf("%d",&r[i]);
     }

     for(i=0;i<num;i++)
     {
          r_m=r_m+r[i];
     }
     R_m=(float)r_m/num;

     ucl=D4*R_m;
     lcl=D3*R_m;

     printf("\nthe value of central line R_m =  %.3f",R_m);
     printf("\nthe value of upper control limit ucl =  %.3f",ucl);
     printf("\nthe value of lower control limit lcl =  %.3f\n",lcl);
}