program calculator;
uses crt;

{add exponents + memory slots}

var
spotfull,mm2,n,c,what,b,deccount,decmult:integer;
c2,c3,answer:real;
x,sign,sign2,gg:char;
quit,dec,neg,sounds_on:boolean;
input:string;

procedure clear_variables;
begin
 {----------------clears all variables---------------------------------------}
 input := ' ';
 c2 := 0;
 c3 := 0;
 spotfull := 0;
 what := 0;
 n := 1;
 dec := false;
 neg := false;
 sign := ' ';
 sign2 := ' ';
 quit := false;

end;


procedure border;
var x:integer;

{----------------Puts a border around the screen----------------------------}
begin
 textcolor (3);
 gotoxy (1,1);
 write (#201);
 for x := 1 to 78 do write (#205);
 write (#187);

 gotoxy (1,24);
 write (#200);
 for x := 1 to 78 do write (#205);
 write (#188);

 for x := 2 to 23 do begin
  gotoxy (80,x);
  write (#186);
  gotoxy (1,x);
  write (#186);
 end;

 gotoxy (1,11);
 write (#199);
 for x := 1 to 78 do write (#196);
 write (#182);

end;


procedure writing;
begin
 {----------------TITLE AND INTRO--------------------------------------------}
 textcolor(green);
 gotoxy (21,3);
 writeln ('~~~~~~~~~~~~The Calculator~~~~~~~~~~~');
 writeln;
 textcolor(7);
 writeln ('     Welcome to the calculator. Press ''h'' for help, but everything works');
 writeln ('     pretty much just like a normal pocket calculator. Basically you just');
 writeln ('     type in a number, a symbol, another number, and then an equal sign.');
 writeln ('     To make a number negative, press ''n'' before you enter in the number.');
 writeln ('     Pressing ''c'' clears everything and pressing ''q'' quits. Have fun');


end;


procedure buttons;
var y:integer;
    y2:char;
begin

 {----------------WRITING NUMBER BUTTONS-------------------------------------}

 gotoxy (2,15);
 write ('             ')   ;

 for y := 0 to 9 do begin
  case y of
   0 : y2 := '0';
   1 : y2 := '1';
   2 : y2 := '2';
   3 : y2 := '3';
   4 : y2 := '4';
   5 : y2 := '5';
   6 : y2 := '6';
   7 : y2 := '7';
   8 : y2 := '8';
   9 : y2 := '9';
  end;
  textcolor(blue);
  if x = y2 then textcolor(red);
  write ('[',y,'] ');
 end;

 textcolor(blue);
 if x = '.' then textcolor(red);
 write ('[.] ');

 textcolor(blue);
 if (x = 'n') or (x = 'N') then textcolor(red);
 write ('[+/-] ');

 {---------------WRITING SYMBOL BUTTONS--------------------------------------}
 gotoxy (2,17);
 write ('             ')   ;

 textcolor(blue);
 if x = '+' then textcolor(red);
 write ('[+] ');

 textcolor(blue);
 if x = '-' then textcolor(red);
 write ('[-] ');

 textcolor(blue);
 if x = '*' then textcolor(red);
 write ('[*] ');

 textcolor(blue);
 if x = '/' then textcolor(red);
 write ('[/] ');

 textcolor(blue);
 if x = '=' then textcolor(red);
 write ('[=] ');

 textcolor(blue);
 if (x = 'c') or (x = 'C') then textcolor(red);
 write ('[C] ');

 textcolor(11);

end;


procedure sounds;
begin

if sounds_on then begin
if x = '=' then begin
sound(750);
delay(1000);
nosound;
end else
if (x = 'Q') or (x = 'C') then begin
sound(300);
delay(1000);
nosound;
end else begin
sound(500);
delay(850);
nosound;
end;
end;
end;


procedure equation;
begin

 {----------------writing user input and answer------------------------------}
 gotoxy (33,20);

 gg := ' ';

 if b <> 5 then write(input)
 else
 write (answer:0:mm2);

 b := 0;
 {----------------input main variable : x------------------------------------}
 gotoxy (80,25);
 x := upcase(readkey);

 {----------------sorting out actions determined by x------------------------}
 case x of
  '0','1','2','3','4','5','6','7','8','9' : begin
   if dec = true then if what = 5 then n := n + 1;
   sounds;
   input := input + x;
   what := 5;
  end;
  '+','-','*','/','=' : begin
   if what <> 5 then x := ' '
   else
   begin
    sounds;
    spotfull := spotfull + 1;
    input := input + x;
    neg := false;
    dec := false;
   end;
   n := 1;
   what := 6;
  end;
  '.' : begin
   if dec = true then x := ' ';
   if dec = false then begin
   sounds;
   input := input + x;
   what := 7;
   end;
   dec := true;
  end;
  'N' : begin
   if (what <> 5) and (what <> 7) and (neg = false) then begin
    sounds;
    neg := true;
    input := input + '-';
    what := 8;
   end
   else x := ' ';
  end;
  'C' : begin
   clear_variables;
   sounds;
   end;
  #27,'Q' : begin
   sounds;
   quit := true;
   x := ' ';
  end
  else
  if x <> 'H' then x := ' ';
 end;

 {----------------COMPUTATION------------------------------------------------}
 if (x <> ' ') and (x <> 'C') and (x <> 'Q') and (x <> 'H') then
  begin

  {----------------getting variable x into sign holder or integer-------------}
  if x = '=' then sign2 := sign;
  if (what = 6) and (spotfull = 2) then sign2 := sign;
  case x of
   '0' : c := 0;
   '1' : c := 1;
   '2' : c := 2;
   '3' : c := 3;
   '4' : c := 4;
   '5' : c := 5;
   '6' : c := 6;
   '7' : c := 7;
   '8' : c := 8;
   '9' : c := 9;
   else
   if (what <> 8) and (x <> '.') then sign := x;
  end;

  {----------------putting together negitive whole numbers--------------------}
  if (what = 5) and (dec = false) and (neg = true) then
  if sign = ' ' then c2 := c2 * 10 - c
  else
  c3 := c3 * 10 - c;

{----------------putting together decimal numbers (pos and neg)-------------}
  if (what = 5) and (dec = true) then begin
   decmult := 1;
   deccount := 0;
   repeat
    decmult := decmult * 10;
    deccount := deccount + 1;
   until deccount = n;
   if (sign = ' ') and (neg = false) then c2 := c2 + c / decmult
   else
   if (sign <> ' ') and (neg = false) then c3 := c3 + c / decmult
   else
   if (sign = ' ') and (neg = true) then c2 := c2 - c / decmult
   else
   if (sign <> ' ') and (neg = true) then c3 := c3 - c / decmult;
  end;

  {-----------------putting together positive whole numbers-------------------}
  if (what = 5) and (dec = false) and (neg = false) then begin
   if sign = ' ' then c2 := c2 * 10 + c
   else
   c3 := c3 * 10 + c;
  end;

  {-----------------more than 2 number answer (2+2+2)-------------------------}
  if (spotfull = 2) and (what = 6) and (sign <> '=') then begin
   case sign2 of
    '+' : c2 := c2 + c3;
    '-' : c2 := c2 - c3;
    '*' : c2 := c2 * c3;
    '/' : begin
     if c3 <> 0 then c2 := c2 / c3
     else
     begin
      clear_variables;
      x := ' ';
      gotoxy (30,18);
      writeln ('Can''t divide by 0');
      gotoxy (80,25);
      gg := readkey;
     end;
    end;
   end;
   c3 := 0;
   spotfull := 1;
  end;

  {------------------final = sign answer-------------------------------------}
  if (what = 6) and (sign = '=') then begin
   if spotfull = 2 then begin
    case sign2 of
     '+' : answer := c2 + c3;
     '-' : answer := c2 - c3;
     '*' : answer := c2 * c3;
     '/' : begin
      if c3 <> 0 then answer := c2 / c3
      else
      begin
       clear_variables;
       x := ' ';
       gotoxy (30,18);
       writeln ('Can''t divide by 0');
       gotoxy (80,25);
       gg := readkey;
       gg := '}';
      end;
     end;
    end;
   end
   else
   answer := c2;
   if gg <> '}' then b := 5;
   clear_variables;
  end;

 end;

end;


procedure decimal;
begin

 {----------------changing number of decimal places in answer----------------}
 textcolor (green);
 writeln ('      How many decimal places should be displayed in the answer?');
 write ('      (0 through 9)');
 gg := readkey;

 case gg of
  '0' : mm2 := 0;
  '1' : mm2 := 1;
  '2' : mm2 := 2;
  '3' : mm2 := 3;
  '4' : mm2 := 4;
  '5' : mm2 := 5;
  '6' : mm2 := 6;
  '7' : mm2 := 7;
  '8' : mm2 := 8;
  '9' : mm2 := 9;
  else begin
   writeln;writeln;
   textcolor (red);
   writeln ('A number between 1 and 9, please');
   writeln;
   decimal;
  end;
 end;
end;


procedure help;
begin

 {----------------HELP SECTION-----------------------------------------------}
 clrscr;
 textcolor(green);
 writeln;
 writeln ('Despite my master pascal programming skills, this program probably has a');
 writeln ('couple of bugs, but for you to find one, you pretty much have to go looking');
 writeln ('for them. However, I''ve done my best to clear things up and anything that');
 writeln ('you do find won''t be too horrible.');
 writeln ('One major thing is that this program won''t do order of operations. For');
 writeln ('example:');
 writeln;
 textcolor(red);
 writeln ('Real world : 5 + 2 * 5 = 15');
 writeln ('My program : 5 + 2 * 5 = 35');
 writeln;
 textcolor(green);
 writeln ('But that doesn''t really matter, you just gotta put everything in the right');
 writeln ('order from the start, for example:');
 writeln;
 textcolor(red);
 writeln ('Right way  : 2 * 5 + 5 = 15');
 writeln;
 textcolor(blue);
 writeln ('--More--');
 gg := readkey;

 textcolor(green);
 writeln;
 writeln ('The Calculator can also do negative numbers, but there are also a couple of');
 writeln ('catches here. For one thing, you gotta press ''n'' before you enter in the');
 writeln ('number, not at the end or somewhere in the middle. Secondly, pressing ''n''');
 writeln ('again won''t turn turn the number back to positive, if you mess up, you gotta');
 writeln ('just clear everything.');
 writeln;
 writeln ('This program also plays sounds when keys are pressed, nothing big, just');
 writeln ('internal speaker stuff, but they do kind of slow things down a tiny bit. If');
 writeln ('you wanna toggle them on and off for some reason, then press ''s'' right now.');
 writeln;
 writeln ('I''ve also set the default number of decimal places that the answer will');
 writeln ('have to 2, but if you want more or less, then you can set it yourself by');
 writeln ('pressing ''d'' right now.');
 writeln;
 textcolor(blue);
 writeln ('Press any key to continue, or ''d'' to configure decimal places, or ''s''');
 writeln ('to toggle sounds');
 gotoxy (80,25);
 textcolor(green);
 gg := upcase(readkey);
 if gg = 'D' then decimal;
 if gg = 'S' then begin
  textcolor(green);
  writeln;
  writeln ('Do you want the program to play sounds?');
  write ('(press Y or N)');
  repeat
  gg := upcase(readkey);
  until (gg = 'Y') or (gg = 'N');
  if gg = 'Y' then sounds_on := true else sounds_on := false;
 end;
end;



begin

 {----------------SETUP AND MAIN PROCEDURE STARTUP---------------------------}
 x := ' ';
 mm2 := 2;
 sounds_on := false;
 clear_variables;
 repeat
 clrscr;
 writing;
 border;
 buttons;
 equation;
 if x = 'H' then help;
 until quit;
 clrscr;
end.