<s>
Atari	B-Language
BASIC	I-Language
is	O
an	O
interpreter	B-Application
for	O
the	O
BASIC	O
programming	O
language	O
that	O
shipped	O
with	O
the	O
Atari	B-Device
8-bit	I-Device
family	I-Device
of	O
6502-based	O
home	O
computers	O
.	O
</s>
<s>
Unlike	O
most	O
American	O
BASICs	O
of	O
the	O
home	O
computer	O
era	O
,	O
Atari	B-Language
BASIC	I-Language
is	O
not	O
a	O
derivative	O
of	O
Microsoft	B-Language
BASIC	I-Language
and	O
differs	O
in	O
significant	O
ways	O
.	O
</s>
<s>
The	O
language	O
was	O
distributed	O
as	O
an	O
8KB	O
ROM	B-Protocol
cartridge	I-Protocol
for	O
use	O
with	O
the	O
1979	O
Atari	O
400	O
and	O
800	O
computers	O
.	O
</s>
<s>
Starting	O
with	O
the	O
600XL	B-Device
and	O
800XL	B-Device
in	O
1983	O
,	O
BASIC	O
is	O
built	O
into	O
the	O
system	O
.	O
</s>
<s>
Despite	O
the	O
Atari	B-Device
8-bit	I-Device
computers	I-Device
running	O
at	O
a	O
higher	O
speed	O
than	O
most	O
of	O
its	O
contemporaries	O
,	O
several	O
technical	O
decisions	O
placed	O
Atari	B-Language
BASIC	I-Language
near	O
the	O
bottom	O
in	O
performance	O
benchmarks	O
.	O
</s>
<s>
The	O
original	O
authors	O
addressed	O
most	O
of	O
these	O
issues	O
in	O
a	O
series	O
of	O
improved	O
versions	O
:	O
BASIC	B-Language
A+	I-Language
(	O
1981	O
)	O
,	O
BASIC	O
XL	O
(	O
1983	O
)	O
,	O
and	O
BASIC	O
XE	O
(	O
1985	O
)	O
.	O
</s>
<s>
A	O
host	O
of	O
third-party	O
interpreters	B-Application
and	O
compilers	O
like	O
Turbo-Basic	B-Language
XL	I-Language
also	O
appeared	O
.	O
</s>
<s>
The	O
complete	O
,	O
annotated	O
source	O
code	O
and	O
design	O
specifications	O
of	O
Atari	B-Language
BASIC	I-Language
were	O
published	O
as	O
The	O
Atari	B-Language
BASIC	I-Language
Source	O
Book	O
in	O
1983	O
.	O
</s>
<s>
The	O
machines	O
that	O
would	O
become	O
the	O
Atari	B-Device
8-bit	I-Device
family	I-Device
were	O
originally	O
developed	O
as	O
second-generation	O
video	B-Device
game	I-Device
consoles	I-Device
intended	O
to	O
replace	O
the	O
Atari	B-General_Concept
VCS	I-General_Concept
.	O
</s>
<s>
In	O
early	O
1978	O
,	O
Atari	O
licensed	O
the	O
source	O
code	O
to	O
the	O
MOS	B-General_Concept
6502	I-General_Concept
version	O
of	O
Microsoft	B-Language
BASIC	I-Language
.	O
</s>
<s>
It	O
was	O
offered	O
in	O
two	O
versions	O
:	O
one	O
using	O
a	O
32-bit	O
floating	B-Algorithm
point	I-Algorithm
format	I-Algorithm
that	O
was	O
about	O
7800bytes	O
when	O
compiled	O
,	O
and	O
another	O
using	O
an	O
extended	O
40-bit	O
format	O
that	O
was	O
close	O
to	O
9KB	O
.	O
</s>
<s>
Even	O
the	O
32-bit	O
version	O
barely	O
fit	O
into	O
the	O
8KB	O
size	O
of	O
the	O
machine	O
's	O
ROM	B-Protocol
cartridge	I-Protocol
format	O
.	O
</s>
<s>
Atari	O
also	O
felt	O
that	O
they	O
needed	O
to	O
expand	O
the	O
language	O
to	O
support	O
the	O
hardware	O
features	O
of	O
their	O
computers	O
,	O
similar	O
to	O
what	O
Apple	O
had	O
done	O
with	O
Applesoft	B-Language
BASIC	I-Language
.	O
</s>
<s>
This	O
increased	O
the	O
size	O
of	O
Atari	O
's	O
version	O
to	O
around	O
11KB	O
;	O
AppleSoft	B-Language
BASIC	I-Language
on	O
the	O
Apple	O
II+	O
was	O
10,240	O
bytes	O
long	O
.	O
</s>
<s>
In	O
September	O
1978	O
,	O
Shepardson	B-Device
Microsystems	I-Device
won	O
the	O
bid	O
on	O
completing	O
BASIC	O
.	O
</s>
<s>
At	O
the	O
time	O
they	O
were	O
finishing	O
Cromemco	O
16K	O
Structured	O
BASIC	O
for	O
the	O
Z80-based	O
Cromemco	O
S-100	B-Architecture
bus	I-Architecture
machines	O
.	O
</s>
<s>
Developers	O
Kathleen	O
O'Brien	O
and	O
Paul	O
Laughton	O
used	O
Data	B-Language
General	I-Language
Business	I-Language
Basic	I-Language
,	O
an	O
integer-only	O
implementation	O
,	O
as	O
the	O
inspiration	O
for	O
their	O
BASIC	O
,	O
given	O
Laughton	O
's	O
experience	O
with	O
Data	O
General	O
on	O
a	O
time-sharing	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Cromemco	O
BASIC	O
included	O
an	O
extended	O
floating	B-Algorithm
point	I-Algorithm
implementation	O
using	O
a	O
14-digit	O
binary	O
coded	O
decimal	O
(	O
BCD	O
)	O
format	O
made	O
possible	O
using	O
all	O
16	O
registers	O
of	O
the	O
Zilog	B-General_Concept
Z80	I-General_Concept
processor	O
.	O
</s>
<s>
Even	O
the	O
smallest	O
BASICs	O
on	O
the	O
6502	B-General_Concept
generally	O
used	O
about	O
10K	O
,	O
for	O
instance	O
,	O
Commodore	B-Language
BASIC	I-Language
used	O
9K	O
but	O
also	O
relied	O
on	O
support	O
from	O
the	O
KERNAL	B-Operating_System
,	O
while	O
Applesoft	B-Language
BASIC	I-Language
used	O
10780	O
bytes	O
.	O
</s>
<s>
To	O
meet	O
the	O
goal	O
of	O
fitting	O
in	O
an	O
8K	O
ROM	O
,	O
the	O
new	O
BASIC	O
would	O
be	O
in	O
two	O
parts	O
,	O
the	O
language	O
itself	O
on	O
the	O
cartridge	B-Protocol
,	O
and	O
a	O
separate	O
FP	O
library	O
using	O
2K	O
in	O
the	O
system	O
's	O
10K	O
ROM	O
.	O
</s>
<s>
To	O
fit	O
within	O
2k	O
,	O
the	O
floating-point	B-Algorithm
system	O
supported	O
only	O
the	O
6-digit	O
format	O
.	O
</s>
<s>
Atari	O
's	O
plans	O
were	O
to	O
take	O
an	O
early	O
8K	O
version	O
of	O
Microsoft	B-Language
BASIC	I-Language
to	O
the	O
1979	O
CES	O
,	O
then	O
switch	O
to	O
Atari	B-Language
BASIC	I-Language
for	O
production	O
.	O
</s>
<s>
Atari	O
took	O
an	O
8K	O
cartridge	B-Protocol
version	O
to	O
CES	O
instead	O
of	O
Microsoft	O
's	O
.	O
</s>
<s>
Atari	B-Language
Microsoft	I-Language
BASIC	I-Language
later	O
became	O
available	O
as	O
a	O
separate	O
product	O
.	O
</s>
<s>
Revision	O
B	O
attempted	O
to	O
fix	O
the	O
major	O
bugs	O
in	O
Revision	O
A	O
and	O
was	O
released	O
in	O
1983	O
as	O
a	O
built-in	O
ROM	O
in	O
the	O
600XL	B-Device
and	O
800XL	B-Device
models	O
.	O
</s>
<s>
Mapping	O
the	O
Atari	O
described	O
these	O
as	O
"	O
awesome	O
bugs	O
"	O
and	O
advised	O
Revision	O
B	O
owners	O
"	O
Do	O
n't	O
fool	O
around	O
;	O
get	O
the	O
new	O
ROM	O
,	O
which	O
is	O
available	O
on	O
cartridge	B-Protocol
"	O
from	O
Atari	O
.	O
</s>
<s>
The	O
book	O
provides	O
a	O
type-in	O
program	O
to	O
patch	O
Revision	O
B	O
to	O
Revision	O
C	O
for	O
those	O
without	O
the	O
cartridge	B-Protocol
.	O
</s>
<s>
It	O
is	O
built-in	O
on	O
later	O
versions	O
of	O
the	O
800XL	B-Device
and	O
all	O
XE	O
models	O
including	O
the	O
XEGS	O
.	O
</s>
<s>
Revision	O
C	O
was	O
also	O
available	O
as	O
a	O
cartridge	B-Protocol
.	O
</s>
<s>
The	O
version	O
can	O
be	O
determined	O
by	O
typing	O
PRINT	O
PEEK(43234 )	O
at	O
the	O
READY	O
prompt	O
.	O
</s>
<s>
Like	O
most	O
home	O
computer	O
BASICs	O
,	O
Atari	B-Language
BASIC	I-Language
is	O
anchored	O
around	O
its	O
line	B-Application
editor	I-Application
.	O
</s>
<s>
Atari	B-Language
BASIC	I-Language
's	O
editor	O
catches	O
many	O
errors	O
that	O
would	O
not	O
be	O
noticed	O
in	O
MS-derived	O
versions	O
.	O
</s>
<s>
If	O
an	O
error	O
is	O
found	O
,	O
the	O
editor	O
re-displays	O
the	O
line	O
,	O
highlighting	O
the	O
text	O
near	O
the	O
error	O
in	O
inverse	B-General_Concept
video	I-General_Concept
.	O
</s>
<s>
Errors	O
are	O
displayed	O
as	O
numeric	B-Algorithm
codes	O
,	O
with	O
the	O
descriptions	O
printed	O
in	O
the	O
manual	O
.	O
</s>
<s>
Because	O
of	O
the	O
way	O
the	O
line	B-Application
editor	I-Application
works	O
,	O
the	O
user	O
can	O
immediately	O
fix	O
the	O
error	O
.	O
</s>
<s>
If	O
there	O
's	O
no	O
line	O
number	O
,	O
the	O
interpreter	B-Application
assigns	O
it	O
the	O
number	O
-1	O
(	O
800016	O
)	O
and	O
the	O
commands	O
are	O
executed	O
immediately	O
,	O
in	O
"	O
immediate	O
mode	O
"	O
.	O
</s>
<s>
Atari	B-Language
BASIC	I-Language
allows	O
all	O
commands	O
to	O
be	O
executed	O
in	O
both	O
modes	O
.	O
</s>
<s>
For	O
example	O
,	O
LIST	O
can	O
be	O
used	O
inside	O
a	O
program	O
,	O
whereas	O
in	O
many	O
interpreters	B-Application
this	O
would	O
be	O
available	O
in	O
immediate	O
mode	O
only	O
.	O
</s>
<s>
;	O
GOTO	B-Application
has	O
a	O
synonym	O
,	O
GO	O
TO	O
;	O
and	O
LET	O
has	O
a	O
synonym	O
which	O
is	O
the	O
empty	O
string	O
(	O
so	O
and	O
mean	O
the	O
same	O
thing	O
)	O
.	O
</s>
<s>
MS	B-Language
BASICs	I-Language
also	O
allowed	O
?	O
</s>
<s>
Atari	B-Language
BASIC	I-Language
's	O
tokenizer	O
scans	O
the	O
text	O
,	O
converting	O
each	O
keyword	O
to	O
a	O
single-byte	O
token	O
(	O
for	O
example	O
,	O
is	O
2016	O
)	O
,	O
each	O
number	O
to	O
a	O
six-byte	O
floating	B-Algorithm
point	I-Algorithm
value	I-Algorithm
,	O
each	O
variable	O
name	O
to	O
an	O
index	O
into	O
a	O
table	O
,	O
and	O
so	O
on	O
,	O
until	O
the	O
line	O
is	O
fully	O
turned	O
into	O
an	O
easy	O
to	O
interpret	O
format	O
.	O
</s>
<s>
Shepardson	O
referred	O
to	O
this	O
complete-tokenizing	O
concept	O
as	O
a	O
"	O
pre-compiling	O
interpreter	B-Application
"	O
.	O
</s>
<s>
String	O
variables	O
have	O
their	O
own	O
area	O
(	O
pointed	O
to	O
at	O
STARP	O
8C	O
,	O
8D16	O
)	O
as	O
does	O
the	O
runtime	O
stack	O
(	O
pointed	O
to	O
at	O
RUNSTK	O
8E	O
,	O
8F16	O
)	O
used	O
to	O
store	O
the	O
line	O
numbers	O
of	O
looping	O
statements	O
(	O
FOR	O
...	O
NEXT	O
)	O
and	O
subroutines	O
(	O
GOSUB	B-Device
...	O
RETURN	O
)	O
.	O
</s>
<s>
Atari	B-Language
BASIC	I-Language
includes	O
three	O
trigonometric	O
functions	O
:	O
sine	O
,	O
cosine	O
,	O
and	O
arc	O
tangent	O
.	O
</s>
<s>
Atari	B-Language
BASIC	I-Language
copied	O
the	O
string-handling	O
system	O
of	O
Hewlett-Packard	B-Language
BASIC	I-Language
,	O
where	O
the	O
basic	O
data	O
type	O
is	O
a	O
single	O
character	O
,	O
and	O
strings	O
are	O
arrays	O
of	O
characters	O
.	O
</s>
<s>
Arrays	O
are	O
not	O
initialized	O
,	O
so	O
a	O
numeric	B-Algorithm
array	O
or	O
string	O
contains	O
whatever	O
data	O
was	O
in	O
memory	O
when	O
it	O
was	O
allocated	O
.	O
</s>
<s>
Numeric	B-Algorithm
arrays	O
can	O
only	O
be	O
cleared	O
with	O
a	O
FOR	O
...	O
NEXT	O
loop	O
:	O
</s>
<s>
Numeric	B-Algorithm
values	O
in	O
DATA	O
statements	O
are	O
read	O
as	O
strings	O
or	O
as	O
numbers	O
according	O
to	O
the	O
type	O
of	O
the	O
variable	O
they	O
are	O
read	O
into	O
.	O
</s>
<s>
The	O
Atari	O
OS	B-General_Concept
includes	O
a	O
subsystem	O
for	O
peripheral	O
device	O
input/output	O
(	O
I/O	O
)	O
known	O
as	O
CIO	O
(	O
Central	O
Input/Output	O
)	O
.	O
</s>
<s>
New	O
device	O
drivers	O
could	O
be	O
written	O
fairly	O
easily	O
that	O
would	O
automatically	O
be	O
available	O
to	O
Atari	B-Language
BASIC	I-Language
and	O
any	O
other	O
program	O
using	O
the	O
Atari	O
OS	B-General_Concept
,	O
and	O
existing	O
drivers	O
could	O
be	O
supplanted	O
or	O
augmented	O
by	O
new	O
ones	O
.	O
</s>
<s>
A	O
replacement	O
,	O
for	O
example	O
could	O
displace	O
the	O
one	O
in	O
ROM	O
to	O
provide	O
an	O
80-column	O
display	O
,	O
or	O
to	O
piggyback	O
on	O
it	O
to	O
generate	O
a	O
checksum	B-Algorithm
whenever	O
a	O
line	O
is	O
returned	O
(	O
such	O
as	O
used	O
to	O
verify	O
a	O
type-in	O
program	O
listing	O
)	O
.	O
</s>
<s>
Atari	B-Language
BASIC	I-Language
supports	O
CIO	O
access	O
with	O
reserved	O
words	O
and	O
.	O
</s>
<s>
There	O
are	O
routines	O
in	O
the	O
OS	B-General_Concept
for	O
simple	O
graphics	O
drawing	O
functions	O
but	O
not	O
all	O
are	O
available	O
as	O
specific	O
BASIC	O
keywords	O
.	O
</s>
<s>
Here	O
,	O
means	O
"	O
ensure	O
channel	O
1	O
is	O
free	O
,	O
"	O
call	O
the	O
driver	O
to	O
prepare	O
the	O
device	O
(	O
this	O
will	O
set	O
the	O
cassette	B-Device
tape	I-Device
spools	O
onto	O
tension	O
and	O
advance	O
the	O
heads	O
keeping	O
the	O
cassette	B-Device
tape	I-Device
player	O
"	O
paused	O
"	O
.	O
</s>
<s>
Typing	O
from	O
BASIC	O
exits	O
to	O
the	O
Atari	B-Operating_System
DOS	I-Operating_System
command	O
menu	O
.	O
</s>
<s>
Atari	B-Language
BASIC	I-Language
supports	O
sound	O
,	O
(	O
via	O
the	O
statement	O
)	O
,	O
graphics	O
(	O
)	O
,	O
and	O
controllers	O
(	O
)	O
.	O
</s>
<s>
Advanced	O
capabilities	O
of	O
the	O
hardware	O
such	O
as	O
higher	O
pitch	O
resolution	O
,	O
high-pass	O
filters	O
,	O
digitised	O
sound	O
and	O
waveforms	O
,	O
player/missile	O
graphics	O
(	O
sprites	O
)	O
,	O
redefined	O
character	O
sets	O
,	O
scrolling	O
,	O
and	O
custom	O
graphics	O
modes	O
are	O
not	O
supported	O
by	O
BASIC	O
;	O
these	O
will	O
require	O
machine	O
language	O
routines	O
or	O
PEEK/POKE	B-Language
statements	O
.	O
</s>
<s>
A	O
few	O
of	O
the	O
17	O
basic	O
character/graphics	O
modes	O
supported	O
by	O
the	O
hardware	O
cannot	O
be	O
simply	O
accessed	O
from	O
BASIC	O
on	O
the	O
Atari	O
400/800	O
as	O
the	O
OS	B-General_Concept
ROMs	O
do	O
not	O
support	O
them	O
.	O
</s>
<s>
The	O
OS	B-General_Concept
ROMs	O
on	O
the	O
XL/XE	O
added	O
support	O
for	O
these	O
modes	O
except	O
for	O
ANTIC	O
mode	O
3	O
,	O
which	O
requires	O
a	O
character	O
set	O
redefined	O
in	O
RAM	O
to	O
operate	O
correctly	O
.	O
</s>
<s>
If	O
bitmap	O
mode	O
in	O
full	O
screen	O
is	O
invoked	O
Atari	B-Language
BASIC	I-Language
will	O
gracefully	O
switch	O
back	O
into	O
text	O
mode	O
when	O
program	O
execution	O
is	O
terminated	O
,	O
avoiding	O
leaving	O
the	O
user	O
with	O
an	O
unresponsive	O
screen	O
that	O
must	O
be	O
escaped	O
by	O
typing	O
a	O
blind	O
command	O
or	O
resetting	O
the	O
computer	O
.	O
</s>
<s>
If	O
Atari	B-Language
BASIC	I-Language
attempts	O
to	O
plot	O
beyond	O
the	O
allowed	O
coordinates	O
for	O
the	O
mode	O
a	O
runtime	O
error	O
occurs	O
.	O
</s>
<s>
Atari	B-Language
BASIC	I-Language
allows	O
numeric	B-Algorithm
variables	O
and	O
expressions	O
to	O
be	O
used	O
to	O
supply	O
line	O
numbers	O
to	O
GOTO	B-Application
and	O
GOSUB	B-Device
commands	O
.	O
</s>
<s>
For	O
instance	O
,	O
a	O
subroutine	O
that	O
clears	O
the	O
screen	O
can	O
be	O
written	O
as	O
GOSUB	B-Device
CLEARSCREEN	O
,	O
which	O
is	O
easier	O
to	O
understand	O
than	O
GOSUB	B-Device
10000	O
.	O
</s>
<s>
This	O
is	O
particularly	O
useful	O
for	O
achieving	O
rapid	O
vertical	O
movement	O
of	O
player/missile	O
images	O
directly	O
from	O
Atari	B-Language
BASIC	I-Language
.	O
</s>
<s>
Numeric	B-Algorithm
variables	O
and	O
expressions	O
can	O
be	O
used	O
as	O
the	O
parameter	O
for	O
the	O
RESTORE	O
statement	O
,	O
allowing	O
DATA	O
statements	O
to	O
be	O
randomly	O
accessed	O
through	O
code	O
such	O
as	O
.	O
</s>
<s>
Atari	B-Language
BASIC	I-Language
can	O
call	O
machine	O
code	O
subroutines	O
stored	O
in	O
strings	O
or	O
POKEed	O
into	O
memory	O
.	O
</s>
<s>
In	O
theory	O
,	O
Atari	B-Language
BASIC	I-Language
should	O
run	O
faster	O
than	O
contemporary	O
BASICs	O
based	O
on	O
the	O
MS	O
pattern	O
.	O
</s>
<s>
In	O
spite	O
of	O
these	O
theoretical	O
advantages	O
,	O
in	O
practice	O
,	O
Atari	B-Language
BASIC	I-Language
is	O
slower	O
than	O
most	O
other	O
home	O
computer	O
BASICs	O
,	O
often	O
by	O
a	O
large	O
amount	O
.	O
</s>
<s>
On	O
two	O
widely	O
used	O
benchmarks	O
of	O
the	O
era	O
,	O
Byte	O
magazine	O
's	O
Sieve	B-Language
of	I-Language
Eratosthenes	I-Language
and	O
the	O
Creative	O
Computing	O
benchmark	O
test	O
written	O
by	O
David	O
H	O
.	O
Ahl	O
,	O
the	O
Atari	O
finished	O
near	O
the	O
end	O
of	O
the	O
list	O
in	O
terms	O
of	O
performance	O
,	O
and	O
was	O
much	O
slower	O
than	O
the	O
contemporary	O
Apple	B-Device
II	I-Device
or	O
Commodore	B-Device
PET	I-Device
,	O
in	O
spite	O
of	O
having	O
the	O
same	O
CPU	O
but	O
running	O
it	O
at	O
roughly	O
twice	O
the	O
speed	O
of	O
either	O
.	O
</s>
<s>
The	O
first	O
is	O
that	O
the	O
floating-point	B-Algorithm
math	I-Algorithm
routines	O
are	O
poorly	O
optimized	O
.	O
</s>
<s>
The	O
conversion	O
between	O
floating-point	B-Algorithm
and	O
16-bit	O
integers	O
is	O
also	O
particularly	O
slow	O
.	O
</s>
<s>
Another	O
issue	O
is	O
how	O
Atari	B-Language
BASIC	I-Language
implements	O
branches	O
.	O
</s>
<s>
To	O
perform	O
a	O
branch	O
in	O
a	O
GOTO	B-Application
or	O
GOSUB	B-Device
,	O
the	O
interpreter	B-Application
searches	O
through	O
the	O
entire	O
program	O
for	O
the	O
matching	O
line	O
number	O
.	O
</s>
<s>
When	O
a	O
FOR	B-Language
statement	I-Language
is	O
executed	O
,	O
Atari	B-Language
BASIC	I-Language
records	O
its	O
line	O
number	O
.	O
</s>
<s>
All	O
other	O
BASICs	O
instead	O
record	O
the	O
memory	O
location	O
of	O
the	O
FOR	B-Language
statement	I-Language
and	O
can	O
immediately	O
return	O
to	O
it	O
without	O
having	O
to	O
search	O
.	O
</s>
<s>
One	O
may	O
contrast	O
this	O
philosophy	O
with	O
that	O
of	O
Steve	O
Wozniak	O
's	O
Apple	B-Language
BASIC	I-Language
for	O
the	O
original	O
Apple	B-Device
I	I-Device
which	O
was	O
designed	O
specifically	O
to	O
have	O
the	O
performance	O
required	O
to	O
write	O
games	O
:	O
</s>
<s>
On	O
the	O
Ahl	O
benchmark	O
,	O
Atari	B-Language
BASIC	I-Language
required	O
405	O
seconds	O
,	O
while	O
exactly	O
the	O
same	O
code	O
in	O
Turbo-BASIC	B-Language
XL	I-Language
took	O
41.6	O
seconds	O
,	O
an	O
order	O
of	O
magnitude	O
improvement	O
.	O
</s>
<s>
The	O
following	O
keywords	O
are	O
not	O
in	O
Atari	B-Language
BASIC	I-Language
:	O
INKEY$	O
,	O
CLS	O
,	O
DEF	O
FN	O
,	O
SPC	O
,	O
TAB	O
,	O
ELSE	O
.	O
</s>
<s>
All	O
arrays	O
must	O
be	O
dimensioned	O
prior	O
to	O
use	O
while	O
Microsoft	B-Language
BASIC	I-Language
defaults	O
an	O
array	O
to	O
10	O
elements	O
if	O
not	O
dimensioned	O
.	O
</s>
<s>
MS	B-Language
BASIC	I-Language
stores	O
strings	O
on	O
the	O
heap	O
and	O
sometimes	O
pauses	O
for	O
garbage	B-General_Concept
collection	I-General_Concept
.	O
</s>
<s>
as	O
in	O
Microsoft	B-Language
BASIC	I-Language
,	O
but	O
Atari	B-Language
BASIC	I-Language
does	O
not	O
tokenize	O
it	O
into	O
PRINT	O
.	O
</s>
<s>
The	O
target	O
of	O
GOTO	B-Application
and	O
GOSUB	B-Device
can	O
be	O
a	O
variable	O
or	O
expression	O
.	O
</s>
<s>
FOR	O
..	O
NEXT	O
loops	O
in	O
Atari	B-Language
BASIC	I-Language
must	O
have	O
a	O
variable	O
name	O
referenced	O
by	O
the	O
NEXT	O
statement	O
while	O
Microsoft	B-Language
BASIC	I-Language
does	O
not	O
require	O
it	O
.	O
</s>
<s>
Multiple	O
variables	O
are	O
not	O
permitted	O
with	O
NEXT	O
statements	O
as	O
they	O
are	O
in	O
Microsoft	B-Language
BASIC	I-Language
(	O
e.g.	O
,	O
NEXT	O
X	O
,	O
Y	O
)	O
.	O
</s>
<s>
+	O
Atari	B-Language
BASIC	I-Language
keywords	O
Keyword	O
Description	O
ABS	O
Returns	O
the	O
absolute	O
value	O
of	O
a	O
number	O
ADR	O
Returns	O
the	O
address	O
in	O
memory	O
of	O
a	O
variable	O
(	O
mostly	O
used	O
for	O
machine	O
code	O
routines	O
stored	O
in	O
variables	O
)	O
AND	O
Logical	O
conjunction	O
ASC	O
Returns	O
the	O
ATASCII	B-Protocol
value	O
of	O
a	O
character	O
ATN	O
Returns	O
the	O
arctangent	O
of	O
a	O
number	O
BYE	O
Transfers	O
control	O
to	O
the	O
internal	O
"	O
Self	O
Test	O
"	O
program	O
(	O
"	O
Memo	O
Pad	O
"	O
on	O
early	O
models	O
)	O
CHR$	O
Returns	O
a	O
character	O
given	O
an	O
ATASCII	B-Protocol
value	O
CLOAD	O
Loads	O
from	O
cassette	B-Device
tape	I-Device
a	O
tokenized	O
program	O
that	O
was	O
saved	O
with	O
CSAVE	O
CLOG	O
Returns	O
the	O
common	O
logarithm	O
of	O
a	O
number	O
CLOSE	O
Terminates	O
pending	O
transfers	O
(	O
flush	O
)	O
and	O
closes	O
an	O
I/O	O
channel	O
CLR	O
Clears	O
variables	O
 '	O
memory	O
and	O
program	O
stack	O
COLOR	O
Chooses	O
which	O
logical	O
color	O
to	O
draw	O
in	O
COM	O
Implementation	O
of	O
MS	B-Language
Basic	I-Language
's	O
COMMON	O
was	O
cancelled	O
.	O
</s>
<s>
Recognized	O
but	O
the	O
code	O
for	O
DIM	O
is	O
executed	O
instead	O
CONT	O
Resumes	O
execution	O
of	O
a	O
program	O
after	O
a	O
STOP	O
at	O
the	O
next	O
line	O
number	O
(	O
see	O
STOP	O
)	O
COS	O
Returns	O
the	O
cosine	O
of	O
a	O
number	O
CSAVE	O
Saves	O
to	O
cassette	B-Device
tape	I-Device
a	O
program	O
in	O
tokenized	O
form	O
(	O
see	O
CLOAD	O
)	O
DATA	O
Stores	O
data	O
in	O
lists	O
of	O
numeric	B-Algorithm
or	O
string	O
values	O
DEG	O
Switches	O
trigonometric	O
functions	O
to	O
compute	O
in	O
degrees	O
(	O
radians	O
is	O
the	O
default	O
mode	O
)	O
(	O
see	O
RAD	O
)	O
DIM	O
Defines	O
the	O
size	O
of	O
a	O
string	O
or	O
array	O
(	O
see	O
COM	O
)	O
DOS	O
Transfers	O
control	O
to	O
the	O
Disk	O
Operating	B-General_Concept
System	I-General_Concept
(	O
DOS	O
)	O
;	O
if	O
DOS	O
was	O
not	O
loaded	O
,	O
same	O
as	O
BYE	O
DRAWTO	O
Draws	O
a	O
line	O
to	O
given	O
coordinates	O
END	O
Finishes	O
execution	O
of	O
the	O
program	O
,	O
closes	O
open	O
I/O	O
channels	O
and	O
stops	O
any	O
sound	O
ENTER	O
Loads	O
and	O
merges	O
into	O
memory	O
a	O
plain	O
text	O
program	O
from	O
an	O
external	O
device	O
,	O
usually	O
from	O
cassette	B-Device
tape	I-Device
or	O
disk	O
(	O
see	O
LIST	O
)	O
EXP	O
Exponential	O
function	O
FOR	O
Starts	O
a	O
for	B-Language
loop	I-Language
FRE	O
Returns	O
the	O
amount	O
of	O
free	O
memory	O
in	O
bytes	O
GET	O
Reads	O
one	O
byte	O
from	O
an	O
I/O	O
channel	O
(	O
see	O
PUT	O
)	O
GOSUB	B-Device
Jumps	O
to	O
a	O
subroutine	O
at	O
a	O
given	O
line	O
in	O
the	O
program	O
,	O
placing	O
the	O
return	O
address	O
on	O
the	O
stack	O
(	O
see	O
POP	O
and	O
RETURN	O
)	O
GOTO	B-Application
and	O
GO	O
TO	O
Jumps	O
to	O
a	O
given	O
line	O
in	O
the	O
program	O
.	O
</s>
<s>
GOTO	B-Application
can	O
be	O
omitted	O
in	O
"	O
IF	O
...	O
THEN	O
GOTO	B-Application
...	O
"	O
GRAPHICS	O
Sets	O
the	O
graphics	O
mode	O
IF	O
Executes	O
code	O
depending	O
on	O
whether	O
a	O
condition	O
is	O
true	O
or	O
not	O
INPUT	O
Retrieves	O
a	O
stream	O
of	O
text	O
from	O
an	O
I/O	O
channel	O
;	O
usually	O
data	O
from	O
keyboard	O
(	O
default	O
)	O
,	O
cassette	B-Device
tape	I-Device
or	O
disk	O
INT	O
Returns	O
the	O
floor	O
of	O
a	O
number	O
LEN	O
Returns	O
the	O
length	O
of	O
a	O
string	O
LET	O
Assigns	O
a	O
value	O
to	O
a	O
variable	O
.	O
</s>
<s>
LET	O
can	O
be	O
omitted	O
LIST	O
Lists	O
(	O
all	O
or	O
part	O
of	O
)	O
the	O
program	O
to	O
screen	O
(	O
default	O
)	O
,	O
printer	O
,	O
disk	O
,	O
cassette	B-Device
tape	I-Device
,	O
or	O
any	O
other	O
external	O
device	O
(	O
see	O
ENTER	O
)	O
LOAD	O
Loads	O
a	O
tokenized	O
program	O
from	O
an	O
external	O
device	O
;	O
usually	O
a	O
cassette	B-Device
tape	I-Device
or	O
disk	O
(	O
see	O
SAVE	O
)	O
LOCATE	O
Stores	O
the	O
logical	O
color	O
or	O
ATASCII	B-Protocol
character	O
at	O
given	O
coordinates	O
LOG	O
Returns	O
the	O
natural	O
logarithm	O
of	O
a	O
number	O
LPRINT	O
Prints	O
text	O
to	O
a	O
printer	O
device	O
(	O
same	O
result	O
can	O
be	O
achieved	O
with	O
OPEN	O
,	O
PRINT	O
and	O
CLOSE	O
statements	O
)	O
NEW	O
Erases	O
the	O
program	O
and	O
all	O
the	O
variables	O
from	O
memory	O
;	O
automatically	O
executed	O
before	O
a	O
LOAD	O
or	O
CLOAD	O
NEXT	O
Continues	O
the	O
next	O
iteration	O
of	O
a	O
FOR	B-Language
loop	I-Language
NOT	O
Logical	O
negation	O
NOTE	O
Returns	O
the	O
current	O
position	O
on	O
an	O
I/O	O
channel	O
ON	O
A	O
computed	O
goto	B-Application
or	O
gosub	B-Device
-	O
performs	O
a	O
jump	O
based	O
on	O
the	O
value	O
of	O
an	O
expression	O
OPEN	O
Initialises	O
an	O
I/O	O
channel	O
OR	O
Logical	O
disjunction	O
PADDLE	B-Device
Returns	O
the	O
position	O
of	O
a	O
paddle	B-Device
controller	I-Device
PEEK	B-Language
Returns	O
the	O
value	O
at	O
an	O
address	O
in	O
memory	O
PLOT	O
Draws	O
a	O
point	O
at	O
given	O
coordinates	O
POINT	O
Sets	O
the	O
current	O
position	O
on	O
an	O
I/O	O
channel	O
POKE	B-Language
Sets	O
a	O
value	O
at	O
an	O
address	O
in	O
memory	O
POP	O
Removes	O
a	O
subroutine	O
return	O
address	O
from	O
the	O
stack	O
(	O
see	O
GOSUB	B-Device
and	O
RETURN	O
)	O
POSITION	O
Sets	O
the	O
position	O
of	O
the	O
graphics	O
cursor	O
PRINT	O
and	O
?	O
</s>
