program base_conversion_program;
uses crt;

function topower(base : integer;
                power : integer):longint;

var total,
    temp : longint;
    i : integer;

begin
   total := 1;
   for i := 1 to 32 do
   begin
      temp:=base*total;
      total:=total*base;
      if power = 0 then topower := 1;
      if i = power then topower := total;
   end;
end;

function decimal_binary(decimal : longint): string;

var remain : array[1..32] of integer;
    binary,tempchar : string;
    count,i : integer;

begin
   count := 0;
   binary := '';
   while decimal <> 0 do
   begin
      count := count + 1;
      remain[count] := decimal mod 2;
      decimal := decimal div 2;
   end;
   for i := count downto 1 do
   begin
      str(remain[i],tempchar);
      binary := binary + tempchar;
   end;
   decimal_binary := binary;
   writeln;
end;

function binary_decimal(binary : string): longint;

var  decimal : longint;
     base,power,error,len,i : integer;
     num : array[1..32] of longint;

begin
   decimal := 0;
   base := 2; power := 0;
   len := length(binary);
   for i := len downto 1 do
   begin
      val(binary[i],num[i],error);
      num[i] := num[i]*topower(base,power);
      decimal := decimal + num[i];
      power := power + 1;
   end;
   binary_decimal := decimal;
   writeln; writeln;
end;

procedure readxy(var reply : longint;
                var binary : string;
                row,colour : integer;
                        ok : boolean;
                       max : integer);

procedure centre_line(tempstr : string;
                          row : integer);

var  column : integer;

begin
    window(1,row,80,row); clrscr;
    window(1,1,80,25);
    column := 40-(length(tempstr) div 2);
    gotoxy(column,row);
    write(tempstr);
end;


var  letter : char;
     count,error : integer;
     decimal : string;

begin
   count := 1;
   binary := '';
   str(reply,decimal);
   decimal := ''; textcolor(colour);
   repeat
      letter := readkey;
      if ok=false then
      begin
         if letter=#8 then
         begin
            count := count - 1;
            if count < 1 then count := 1;
            write(chr(8),' ',chr(8));
            delete(binary,count,1);
         end else
         if count <= max then
         if (letter='0') or (letter='1') then
         begin
            count := count + 1;
            binary := binary + letter;
         end;
         centre_line(binary,row);
      end else
      if ok=true then
      begin
         if letter=#8 then
         begin
            count := count - 1;
            if count < 1 then count := 1;
            write(chr(8),' ',chr(8));
            delete(decimal,count,1);
         end else
         if count <= max then
         if (letter>='0') and (letter<='9') then
         begin
            count := count + 1;
            decimal := decimal + letter;
         end;
         centre_line(decimal,row);
      end;
   until letter=#13;
   val(decimal,reply,error);
end;

procedure writexy(text1,text2,text3 : string;
                  row,colour : integer);

var   len,column : integer;
      tempstr : string;

begin
   tempstr := text1+text2+text3;
   len := length(tempstr);
   column := 40-(len div 2);
   textcolor(colour);
   gotoxy(column,row);
   write(tempstr);
   gotoxy(1,25);
end;

procedure menu(var option : integer;
                  var row : integer);

var  pause : char;

begin
   clrscr;
   repeat

      clrscr;
      writexy('Select a base conversion','','',10,4);
      writexy('Decimal To Binary','','',12,6);
      writexy('Binary To Decimal','','',13,6);
      writexy('To The Power','','',14,6);
      writexy('Exit','','',15,6);

      textcolor(4);

      gotoxy(29,row);
      writeln(chr(175));

      gotoxy(51,row);
      writeln(chr(174));

      gotoxy(1,25);
      pause := readkey;
      case pause of
         #72 : row := row - 1;
         #80 : row := row + 1;
      end;

      if row < 12 then row := 12;
      if row > 15 then row := 15;

   until pause = #13;
   option := row-11;
   clrscr;
end;

function commas(no : longint):string;

var count : integer;
    len,i : integer;
    number : string;

begin
   count := 2;
   str(no,number);
   len := length(number);
   for i := len downto 1 do
      if len-count = i then
      begin
         insert(',',number,i);
         count := count + 3;
         if number[1] = #44 then
         delete(number,1,1);
      end;
   commas := number;
end;


{  Start of main program  }


var decimal     : longint;
    binary      : string;
    base,power  : longint;
    option,row  : integer;
    pause       : char;

begin
   textmode(80);
   row := 12;
   while option <> 4 do
   begin
      menu(option,row);
      case option of
         1 :
         begin
            writexy('Enter a decimal number','','',10,6);
            readxy(decimal,binary,11,2,true,10);
            binary := decimal_binary(decimal);
            writexy(commas(decimal),' = ',binary,13,4);
         end;
         2 :
         begin
            writexy('Enter a binary number','','',10,6);
            readxy(decimal,binary,11,2,false,31);
            decimal := binary_decimal(binary);
            writexy(binary,' = ',commas(decimal),13,4);
         end;
         3 :
         begin
            writexy('Enter Base','','',10,6);
            readxy(base,binary,11,2,true,10);
            writexy('Enter Power','','',12,6);
            readxy(power,binary,13,2,true,10); writeln;
            writexy(commas(topower(base,power)),'','',15,4);
         end;
      end;
      if option <> 4 then pause := readkey;
   end;
   textcolor(7);
   clrscr;
end.


{  End of main program  }