program dos_calculator;

{
use the x for multiply and the / for divide


}

{add help page}

uses
   crt;

const
   sign : array[1..4] of char = ('+','-','x','/');


procedure writexy(text : string;
                   row : byte;
                colour : byte);

var
   len    : byte;
   column : byte;

begin
   len := length(text);
   column := 40-(len div 2);
   gotoxy(column,row);
   textcolor(colour);
   write(text);
   gotoxy(1,25);
end;

procedure help_page;

var
   pause : char;

begin
   textcolor(black);
   clrscr;

   writexy('Sum Calculator',8,4);
   writexy('Programmed by Fraser King',9,4);

   writexy('A simple Ms-Dos calculator.',11,6);
   writexy('Use the x for multiply and the / for divide.',12,6);
   writexy('Have a space inbetween each character i.e.',14,6);
   writexy('sum 456 + 345',16,5);
   writexy('sum 350 / 3',18,5);
   writexy('sum 2 x 34 x 45 x 12',20,5);

   pause := readkey;

   textcolor(lightgray);
   clrscr;
   halt;
end;


var
   num      : array[1..32] of real;
   count,i  : byte;
   error    : integer;
   start    : byte;
   tempchar : byte;
   x,y      : byte;
   sum      : real;

begin
   textmode(80);

   if paramstr(1) = '/?' then help_page;

   count := 1;
   for i := 1 to 32 do
   begin
      val(paramstr(count),num[i],error);
      count := count + 2;
   end;

   for i := 1 to 4 do
      if paramstr(2) = sign[i] then
         tempchar := i;

   count := 1; start := 1;
   for i := start to paramcount div 2 do
   begin
      count := count + 1;
      start := start + 2;
   end;

   for i := 1 to count do
   begin
      if frac(num[i]) = 0 then write(num[i]:0:0,' ')
      else write(num[i]:0:2,' ');
      write(sign[tempchar],' ');
   end;

   x := wherex;
   y := wherey;
   gotoxy(x-2,y);
   write('  ');
   gotoxy(x-3,y);
   write(' = ');

   sum := num[1];
   for i := 2 to count do
   case sign[tempchar] of
      '+' : sum := sum + num[i];
      '-' : sum := sum - num[i];
      'x' : sum := sum * num[i];
      '/' : sum := sum / num[i];
   end;

   if frac(sum) = 0 then write(sum:0:0)
   else write(sum:0:2);
end.