<s>
Turbo-BASIC	B-Language
XL	I-Language
is	O
an	O
advanced	O
version	O
of	O
the	O
BASIC	O
programming	O
language	O
for	O
the	O
Atari	B-Device
8-bit	I-Device
family	I-Device
of	O
home	O
computers	O
.	O
</s>
<s>
It	O
is	O
a	O
compatible	O
superset	O
of	O
the	O
Atari	B-Language
BASIC	I-Language
that	O
shipped	O
with	O
the	O
Atari	B-Device
8-bit	I-Device
systems	O
.	O
</s>
<s>
Turbo-Basic	B-Language
XL	I-Language
was	O
developed	O
by	O
Frank	O
Ostrowski	O
and	O
published	O
in	O
the	O
December	O
1985	O
issue	O
of	O
German	O
computer	O
magazine	O
Happy	O
Computer	O
.	O
</s>
<s>
Several	O
modified	O
versions	O
working	O
with	O
different	O
DOS	B-Operating_System
systems	O
have	O
been	O
released	O
by	O
other	O
authors	O
.	O
</s>
<s>
Turbo-Basic	B-Language
XL	I-Language
greatly	O
improves	O
execution	O
over	O
Atari	B-Language
BASIC	I-Language
.	O
</s>
<s>
An	O
Atari	B-Language
BASIC	I-Language
program	O
loaded	O
into	O
Turbo-BASIC	O
,	O
with	O
no	O
changes	O
made	O
,	O
would	O
generally	O
run	O
about	O
three	O
times	O
as	O
fast	O
.	O
</s>
<s>
A	O
Turbo-Basic	B-Language
XL	I-Language
compiler	B-Language
created	O
binary	O
executables	O
,	O
further	O
speeding	O
up	O
program	O
performance	O
to	O
about	O
ten	O
times	O
faster	O
than	O
Atari	B-Language
BASIC	I-Language
.	O
</s>
<s>
Turbo-Basic	B-Language
XL	I-Language
also	O
includes	O
an	O
expanded	O
editor	O
,	O
support	O
for	O
named	O
procedures	O
,	O
and	O
similar	O
block	O
constructs	O
,	O
and	O
added	O
access	O
to	O
the	O
underlying	O
hardware	O
,	O
which	O
,	O
among	O
other	O
things	O
,	O
allowed	O
operation	O
of	O
attached	O
floppy	B-Device
drives	I-Device
without	O
exiting	O
to	O
DOS	B-Operating_System
.	O
</s>
<s>
Ostrowski	O
soon	O
got	O
a	O
job	O
with	O
GFA	O
Systemtechnik	O
GmbH	O
(	O
at	O
the	O
time	O
known	O
as	O
Integral	O
Hydraulik	O
)	O
where	O
he	O
adapted	O
Turbo-Basic	B-Language
XL	I-Language
into	O
GFA	B-Device
BASIC	I-Device
for	O
the	O
Atari	B-Device
ST	I-Device
,	O
which	O
became	O
one	O
of	O
the	O
more	O
popular	O
BASICs	O
on	O
that	O
platform	O
.	O
</s>
<s>
Since	O
their	O
release	O
in	O
1979	O
,	O
the	O
8-bit	O
family	O
normally	O
shipped	O
with	O
a	O
version	O
of	O
Atari	B-Language
BASIC	I-Language
on	O
a	O
ROM	B-Protocol
cartridge	I-Protocol
,	O
or	O
built	O
into	O
the	O
internal	O
ROMs	O
on	O
later	O
machines	O
.	O
</s>
<s>
The	O
poor	O
performance	O
of	O
the	O
official	O
Atari	B-Language
BASIC	I-Language
led	O
to	O
a	O
market	O
for	O
3rd	O
party	O
BASIC	B-Language
interpreters	I-Language
with	O
better	O
performance	O
or	O
more	O
commands	O
.	O
</s>
<s>
Among	O
them	O
was	O
an	O
official	O
port	O
of	O
Microsoft	B-Language
BASIC	I-Language
sold	O
by	O
Atari	O
,	O
several	O
improved	O
versions	O
released	O
by	O
Optimized	B-Operating_System
Systems	I-Operating_System
Software	I-Operating_System
,	O
who	O
had	O
written	O
the	O
original	O
Atari	B-Language
BASIC	I-Language
under	O
contract	O
,	O
and	O
many	O
others	O
.	O
</s>
<s>
There	O
were	O
also	O
several	O
Atari	B-Language
BASIC	I-Language
compilers	B-Language
from	O
a	O
variety	O
of	O
vendors	O
.	O
</s>
<s>
Turbo-Basic	B-Language
XL	I-Language
was	O
a	O
late	O
entry	O
to	O
this	O
list	O
,	O
first	O
published	O
in	O
December	O
1985	O
as	O
type-in	O
program	O
.	O
</s>
<s>
It	O
was	O
unique	O
in	O
that	O
it	O
came	O
in	O
both	O
interpreter	O
and	O
compiler	B-Language
versions	O
.	O
</s>
<s>
This	O
meant	O
that	O
it	O
could	O
not	O
run	O
on	O
the	O
original	O
400/800	O
systems	O
,	O
which	O
led	O
Ostrowski	O
to	O
make	O
a	O
port	O
known	O
as	O
Frost	O
BASIC	O
(	O
short	O
for	O
"	O
Frank	O
Ostrowski	O
"	O
)	O
that	O
was	O
tied	O
to	O
Atari	B-Operating_System
DOS	I-Operating_System
2.0	O
.	O
</s>
<s>
The	O
internal	O
disk-related	O
commands	O
were	O
tied	O
to	O
particular	O
versions	O
of	O
DOS	B-Operating_System
.	O
</s>
<s>
A	O
number	O
of	O
ports	O
to	O
different	O
versions	O
of	O
DOS	B-Operating_System
became	O
available	O
.	O
</s>
<s>
The	O
most	O
notable	O
feature	O
of	O
Turbo-Basic	O
was	O
its	O
dramatically	O
improved	O
speed	O
;	O
an	O
unmodified	O
Atari	B-Language
BASIC	I-Language
program	O
loaded	O
into	O
Turbo-Basic	O
would	O
normally	O
run	O
three	O
to	O
five	O
times	O
faster	O
,	O
and	O
the	O
speed	O
advantage	O
improved	O
as	O
the	O
program	O
size	O
grew	O
.	O
</s>
<s>
This	O
was	O
due	O
largely	O
to	O
a	O
series	O
of	O
improvements	O
on	O
well-known	O
problems	O
in	O
the	O
original	O
Atari	B-Language
BASIC	I-Language
code	O
.	O
</s>
<s>
In	O
MS-derived	O
BASICs	O
the	O
line	O
numbers	O
were	O
stored	O
as	O
16-bit	O
integers	O
and	O
numeric	B-Algorithm
constants	O
in	O
the	O
code	O
in	O
their	O
original	O
ASCII	O
format	O
.	O
</s>
<s>
Atari	B-Language
BASIC	I-Language
worked	O
differently	O
,	O
converting	O
all	O
numeric	B-Algorithm
constants	O
to	O
a	O
6-byte	O
floating-point	B-Algorithm
format	I-Algorithm
when	O
the	O
line	O
was	O
entered	O
.	O
</s>
<s>
This	O
meant	O
the	O
"	O
1000	O
"	O
was	O
no	O
longer	O
in	O
ASCII	O
format	O
and	O
had	O
to	O
be	O
converted	O
from	O
floating-point	B-Algorithm
to	O
integer	O
format	O
.	O
</s>
<s>
FOR	B-Language
...	I-Language
NEXT	I-Language
loops	I-Language
are	O
another	O
common	O
construct	O
in	O
BASIC	O
programs	O
.	O
</s>
<s>
In	O
most	O
BASICs	O
,	O
when	O
the	O
FOR	O
portion	O
was	O
encountered	O
at	O
runtime	O
,	O
its	O
memory	O
location	O
in	O
the	O
source	O
code	O
was	O
pushed	O
onto	O
a	O
call	B-General_Concept
stack	I-General_Concept
so	O
it	O
could	O
easily	O
return	O
to	O
that	O
location	O
when	O
the	O
associated	O
NEXT	O
was	O
encountered	O
.	O
</s>
<s>
For	O
unknown	O
reasons	O
,	O
Atari	B-Language
BASIC	I-Language
pushed	O
the	O
line	O
number	O
of	O
the	O
FOR	O
onto	O
the	O
stack	O
and	O
then	O
looked	O
through	O
the	O
entire	O
code	O
for	O
that	O
line	O
when	O
it	O
encountered	O
the	O
NEXT	O
.	O
</s>
<s>
Turbo-Basic	O
implemented	O
its	O
FOR	B-Language
loops	I-Language
using	O
the	O
address	O
,	O
as	O
was	O
the	O
case	O
in	O
MS	B-Language
BASIC	I-Language
,	O
and	O
thus	O
ran	O
loops	O
with	O
roughly	O
the	O
same	O
performance	O
as	O
MS	O
.	O
</s>
<s>
Line	O
numbers	O
were	O
sent	O
into	O
a	O
hash	B-Error_Name
function	I-Error_Name
that	O
broke	O
them	O
into	O
256-line	O
chunks	O
.	O
</s>
<s>
The	O
other	O
major	O
source	O
of	O
poor	O
performance	O
in	O
Atari	B-Language
BASIC	I-Language
was	O
its	O
very	O
slow	O
binary-coded	O
decimal	O
(	O
BCD	O
)	O
floating	B-Algorithm
point	I-Algorithm
code	O
.	O
</s>
<s>
The	O
library	O
,	O
contained	O
in	O
a	O
separate	O
2K	O
ROM	O
and	O
considered	O
part	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
as	O
opposed	O
to	O
BASIC	O
itself	O
,	O
had	O
been	O
written	O
in	O
a	O
hurry	O
and	O
never	O
optimized	O
.	O
</s>
<s>
Turbo-Basic	O
fixed	O
this	O
by	O
including	O
its	O
own	O
complete	O
floating-point	B-Algorithm
library	O
,	O
which	O
not	O
only	O
fixed	O
many	O
of	O
these	O
issues	O
but	O
also	O
further	O
optimized	O
the	O
code	O
by	O
unrolling	O
small	O
loops	O
.	O
</s>
<s>
Among	O
the	O
extra	O
features	O
of	O
Turbo-Basic	B-Language
XL	I-Language
,	O
added	O
to	O
Atari	B-Language
BASIC	I-Language
,	O
are	O
the	O
following	O
:	O
</s>
