Hexadecimal to Binary Converter (Pascal)

program meng-konversikan bilangan heksadesimal (basis 16)
menjadi bilangan biner (basis 2)

uses crt;

var

  hexa : string;{variable for storing hexa input}

  biner : string;{variable for storing binary output}

  desimal : integer;{temporary variable for decimal conversion}

  index,conv,sub : integer;{variable for looping and subtractor}



BEGIN

clrscr;{clearing the screen}

      {ask for hexa input and read the input}

      write('Input on Hexa : ');readln(hexa);

      {primary loop converter hexa to binary}

      for index:=1 to length(hexa) do

      begin

           {case of hexa written on numeric character}

           if (ord(hexa[index])>=ord('0')) and (ord(hexa[index])<=ord('9')) then              begin                   {ascii code of hexa - ascii code of '0'}                   desimal:=ord(hexa[index])-ord('0');              end              else              {case of hexa written on uppercase letter}              if (ord(hexa[index])>=ord('A')) and (ord(hexa[index])<=ord('F')) then              begin                   {ascii code of hexa - ascii code of 'A'+10}                   {A represent 10 on decimal}                   desimal:=ord(hexa[index])-ord('A')+10;              end              else              {case of hexa written on lowercase letter}              if (ord(hexa[index])>=ord('a')) and (ord(hexa[index])<=ord('f')) then              begin                   {ascii code of hexa - ascii code of 'a'}                   desimal:=ord(hexa[index])-ord('a')+10;              end              else              {case of the input is wrong}              begin                  writeln('INPUTAN SALAH!!');                  readln;                  {terminate the program immediately}                  exit;              end;                 writeln('BINARY');              {the subtractor start on 8 (2^3)}              sub:=8;              for conv:=3 downto 0 do              begin                   {the decimal bigger than subtractor}                   if (desimal>=sub) then

                begin

                     write('1');

                     {subtract the decimal with subtractor}

                     desimal:=desimal-sub;

                end

                else

                begin

                     {write 0 and do nothing}

                     write('0');

                end;

                {decrement the power of subtractor by 1}

                sub:=sub div 2;

                end;

           {just for separating output per character}

           write(' ');

      end;

readln;

END.