Please Explain

[bijay_ps]

I have downloaded this top down parsing program from the net.
but am not able to understand the working of fuction "process". somebody please help me in getting the concept of the program.

#include<iostream.h>
#include<conio.h>
#include<string.h>
class parse
{
int nt,t,m[20][20],i,s,n,p1,q,k,j;
char p[30][30],n1[20],t1[20],ch,b,c,f[30][30],fl[30][30];
public:
int scant(char);
int scannt(char);
void process();
void input();
};

int parse::scannt(char a)
{
  int c=-1,i;
  for(i=0;i<nt;i++)
  {
    if(n1[i]==a)
    { 
      return i;
    }
   }
  return c;
}

int parse::scant(char b)
{
int c1=-1,j;
for(j=0;j<t;j++)
{
if(t1[j]==b)
{
return j;
}
}
return c1;
}


void parse::input()

{
cout<<"Enter the number of productions:";
cin>>n;
cout<<"Enter the productions one by one"<<endl;
for(i=0;i<n;i++)
cin>>p[i];
nt=0;
t=0;
}

void parse::process()
{
  for(i=0;i<n;i++)
  {
    if(scannt(p[i][0])==-1)
    n1[nt++]=p[i][0];
  }
  for(i=0;i<n;i++)
  {
    for(j=3;j<strlen(p[i]);j++)
    {
      if(p[i][j]!='e')
      {
        if(scannt(p[i][j])==-1)
        {
          if((scant(p[i][j]))==-1)
          t1[t++]=p[i][j];
        }
       }
     }
  }
  t1[t++]='$';
  for(i=0;i<nt;i++)
  {
    for(j=0;j<t;j++)
    m[i][j]=-1;
  }
  for(i=0;i<nt;i++)
  {
    cout<<"Enter first["<<n1[i]<<"]:";
    cin>>f[i];
  }

  for(i=0;i<nt;i++)
  {
    cout<<"Enter follow["<<n1[i]<<"]:";
    cin>>fl[i];
  }
  for(i=0;i<n;i++)
  {
    p1=scannt(p[i][0]);
    if((q=scant(p[i][3]))!=-1)
    m[p1][q]=i;
    if((q=scannt(p[i][3]))!=-1)
    {
      for(j=0;j<strlen(f[q]);j++)
      m[p1][scant(f[q][j])]=i;
    }
    if(p[i][3]=='e')
    {
      for(j=0;j<strlen(fl[p1]);j++)
      m[p1][scant(fl[p1][j])]=i;
     }
  }
  for(i=0;i<t;i++)
  cout<<"\t"<<t1[i];
  cout<<endl;
  for(j=0;j<nt;j++)
  {
    cout<<n1[j];
    for(i=0;i<t;i++)
    {
      cout<<"\t"<<" ";
      if(m[j][i]!=-1)
      cout<<p[m[j][i]];
    }
     cout<<endl;
   }
}

void main()
{
clrscr();
parse p;
p.input();
p.process();
getch();
}