program asmd;
uses crt;

{--------------------------------------------------------------------------

program description
                        by 

This program asks you what type of math you want to do, then asks for 2
numbers. Depending on what you answered to the first question, the program
will either add, subtract, multiply, or divide the numbers and then print
the output on the screen. You will then be asked if you want to do more math.
If you do, the program will restart. USES PROCEDURES

Also has added features of :
1. exponent procedure
2. ensure that the user does not divide by 0
3. program runs until the user doesn't want to continue

--------------------------------------------------------------------------}


VAR num1, num2, answer:real ;
what, again:char ;
name:string  ;

{-------------------------------------------------------------}



procedure title;
var
a,b:shortint;
begin

gotoxy (80,25);
gotoxy (17,5);

for b := 1 to 3 do
for a := 1 to 15 do begin
textcolor (a);
write ('-');
end;

textcolor (green);
gotoxy (33,8);
write ('The Calculator');
gotoxy (33,10);
textcolor(red);
writeln ('By ');
gotoxy (17,13);

for b := 1 to 3 do
for a := 1 to 15 do begin
textcolor (a);
write ('-');
end;

gotoxy (50,20);
textcolor(blue);
writeln ('Press any key to Continue');

readkey;
end;



procedure add;
begin
answer := num1 + num2
end;



procedure sub;
begin
answer := num1 - num2
end;



procedure mult;
begin
answer := num1 + num2
end;



procedure divide;
begin
answer := num1 / num2
end;



procedure expon;
var a:shortint;
b : integer;
begin
answer := num1;
b := round(num2);
for a := 2 to b do answer := answer * num1;
end;



begin
clrscr;

title;
clrscr;

textcolor (6);
write ('What''s your name? --->  ');
readln (name);

repeat
if again = 'y' then clrscr;

writeln;
writeln;
textcolor (green);
writeln ('Ok, ',name,', what type of math do you want to do? (type only the function''s first');
writeln ('letter)');
writeln;
write ('Multipy, Divide, Add, Subtract, Exponents --->  ');
what := readkey;
writeln;
what := upcase(what);
writeln;


write ('Enter your first real number with no more than 2 decimal places. --->  ');
readln (num1);
writeln;

repeat

write ('Now enter your second real number with a maxium of 2 decimal places. --->  ');
readln (num2);

until (what <> 'D') or (num2 <> 0);

writeln;



writeln;
writeln;


textcolor (blue);
case what of
'A' : add;
'S' : sub;
'M' : mult;
'D' : divide;
'E' : expon;
end;


case what of
'A' : what := '+';
'S' : what := '-';
'M' : what := '*';
'D' : what := '/';
end;


writeln (num1:0:2,' ',what,' ',num2:0:2,' = ',answer:0:2);


textcolor (green);
writeln;
writeln;
writeln;
writeln ('Hey ',name,', do you want to do some more math?');
write ('Type "y" for yes or "n" for no. --->  ');
again := readkey;
again := upcase(again);

until again = 'N';

end.