(* Techniques : This program demonstrates the use of CASE for slecting choices, calling procedures
                to show the use of string functions COPY, ORD, CHR and procedure STR. *) 
{*Winnie Leung F.4CA  (22) *}
program StringFunction;
uses wincrt;
var  i:integer;
     choice,ans:char;
     

procedure f_copy;
   var strg:string[5];
   begin
       strg:='JAMES';
       writeln('This procedure uses COPY function to show the characters of a word');
       writeln('seperated from the right to the left.');
       writeln('The original string : ',strg);
       writeln('The characters seperated from the right  to the left : ');
       for i:=length(strg) downto 1 do
           writeln(copy(strg,i,1))
   end;

procedure f_ord;
begin writeln;
      writeln('This procedure uses ORD function to print out the ASCII codes of P,Q and R.');
      writeln('ASCII of P is ',ord('P'));
      writeln('ASCII of Q is ',ord('Q'));
      writeln('ASCII of R is ',ord('R'))
end;

procedure f_chr;
begin writeln;
      writeln('This procedure uses CHR function to print out the characters of A,B and C.');
      writeln('The character with ASCII of 65 is ',chr(65));
      writeln('The character with ASCII of 66 is ',chr(66));
      writeln('The character with ASCII of 67 is ',chr(67))
end;


procedure p_str;
var n:integer;
    n_strg:string[4];
    digit:string;
begin
     writeln;
     writeln('This procedure uses STR procedure to show a number converted to a string.');
     writeln('Then print out each digit from the left to the right.');
     writeln('Enter a number not more than 4 digits.');
     readln(n);
     str(n,n_strg);
     for i:=1 to length(n_strg) do
         begin
            write('Character ',i);
            digit:=copy(n_strg,i,1);     
            writeln(' : ',digit)
         end
end;



(*MAIN PROGRAM*)
begin
   writeln('This program demonstrates the use string functions by calling procedures.');
   repeat
   writeln;
   writeln('Press A for calling the demo procedure for COPY function');
   writeln('Press B for calling the demo procedure for ORD function');
   writeln('Press C for calling the demo procedure for CHR function');
   writeln('Press D for calling the demo procedure for STR procedure');
   readln(choice);
   case choice of
   'A': f_copy;
   'B': f_ord;
   'C': f_chr;
   'D': p_str;
    end;
   write('Continue (Y/N) ?');
   readln(ans)
   until ans='N';
  writeln('Good Bye') 
end.