<s>
Atari	B-Application
Assembler	I-Application
Editor	I-Application
(	O
sometimes	O
written	O
as	O
Atari	O
Assembler/Editor	O
)	O
is	O
a	O
ROM	O
cartridge-based	O
development	O
system	O
released	O
by	O
Atari	O
,	O
Inc	O
.	O
in	O
1981	O
.	O
</s>
<s>
It	O
is	O
used	O
to	O
edit	O
,	O
assemble	B-Application
,	O
and	O
debug	O
6502	B-General_Concept
programs	O
for	O
the	O
Atari	B-Device
8-bit	I-Device
family	I-Device
of	O
home	O
computers	O
without	O
the	O
need	O
for	O
additional	O
tools	O
.	O
</s>
<s>
It	O
was	O
programmed	O
by	O
Kathleen	O
O'Brien	O
of	O
Shepardson	B-Device
Microsystems	I-Device
,	O
the	O
company	O
which	O
wrote	O
Atari	B-Language
BASIC	I-Language
,	O
and	O
Assembler	B-Application
Editor	B-Application
shares	O
many	O
design	O
concepts	O
with	O
that	O
language	O
.	O
</s>
<s>
Assembly	O
times	O
are	O
slow	O
,	O
making	O
the	O
cartridge	B-Protocol
challenging	O
to	O
use	O
for	O
larger	O
programs	O
.	O
</s>
<s>
In	O
the	O
manual	O
,	O
Atari	O
recommended	O
the	O
Assembler	B-Application
Editor	B-Application
as	O
a	O
tool	O
for	O
writing	O
subroutines	O
to	O
speed	O
up	O
Atari	B-Language
BASIC	I-Language
,	O
which	O
would	O
be	O
much	O
smaller	O
than	O
full	O
applications	O
.	O
</s>
<s>
The	O
Atari	O
Macro	O
Assembler	B-Application
was	O
offered	O
as	O
an	O
alternative	O
with	O
better	O
performance	O
and	O
more	O
features	O
,	O
such	O
as	O
macros	O
,	O
but	O
it	O
was	O
disk-based	O
,	O
copy-protected	B-Application
,	O
and	O
did	O
not	O
include	O
an	O
editor	B-Application
or	O
debugger	O
.	O
</s>
<s>
Despite	O
the	O
recommendation	O
,	O
commercial	O
software	O
was	O
written	O
using	O
the	O
Assembler	B-Application
Editor	B-Application
,	O
such	O
as	O
the	O
games	O
Eastern	B-Application
Front	I-Application
(	O
1941	O
)	O
,	O
Caverns	B-Application
of	I-Application
Mars	I-Application
,	O
Galahad	B-Application
and	I-Application
the	I-Application
Holy	I-Application
Grail	I-Application
,	O
and	O
Kid	B-Application
Grid	I-Application
.	O
</s>
<s>
The	O
source	O
code	O
to	O
the	O
original	O
Assembler	B-Application
Editor	B-Application
was	O
licensed	O
to	O
Optimized	B-Operating_System
Systems	I-Operating_System
Software	I-Operating_System
who	O
shipped	O
EASMD	O
based	O
on	O
it	O
.	O
</s>
<s>
The	O
Assembler	B-Application
Editor	B-Application
is	O
two-pass	O
6502	B-General_Concept
assembler	B-Application
in	O
an	O
8KB	O
cartridge	B-Protocol
.	O
</s>
<s>
The	O
cartridge	B-Protocol
starts	O
in	O
EDIT	O
mode	O
.	O
</s>
<s>
The	O
programmer	O
enters	O
lines	O
of	O
assembly	O
source	O
into	O
the	O
Atari	O
BASIC-like	O
editor	B-Application
.	O
</s>
<s>
Like	O
Atari	B-Language
BASIC	I-Language
,	O
Assembler	B-Application
Editor	B-Application
included	O
an	O
ENTER	O
command	O
that	O
could	O
be	O
used	O
to	O
combine	O
files	O
together	O
into	O
a	O
single	O
larger	O
program	O
listing	O
.	O
</s>
<s>
Unlike	O
Atari	B-Language
BASIC	I-Language
,	O
Assembler	B-Application
Editor	B-Application
includes	O
commands	O
for	O
automatically	O
creating	O
spaced-out	O
line	O
numbers	O
,	O
as	O
well	O
as	O
renumbering	O
lines	O
and	O
deleting	O
them	O
en	O
masse	O
.	O
</s>
<s>
Values	O
following	O
instructions	O
are	O
normally	O
interpreted	O
as	O
"	O
the	O
value	O
at	O
this	O
memory	O
address	O
"	O
,	O
but	O
an	O
actual	O
numeric	B-Algorithm
value	O
can	O
be	O
provided	O
as	O
an	O
"	O
immediate	O
operand	O
"	O
by	O
appending	O
it	O
with	O
a	O
hash	O
,	O
like	O
LDA	O
#12	O
,	O
which	O
loads	O
the	O
accumulator	O
with	O
the	O
decimal	O
value	O
12	O
.	O
</s>
<s>
Errors	O
are	O
reported	O
with	O
numeric	B-Algorithm
codes	O
that	O
can	O
be	O
looked	O
up	O
in	O
the	O
manual	O
,	O
with	O
about	O
50	O
such	O
codes	O
in	O
total	O
.	O
</s>
<s>
Code	O
can	O
be	O
assembled	O
at	O
any	O
time	O
by	O
typing	O
the	O
ASM	O
command	O
into	O
the	O
editor	B-Application
.	O
</s>
<s>
Assembler	B-Application
Editor	B-Application
was	O
widely	O
derided	O
as	O
the	O
slowest	O
assembler	B-Application
on	O
the	O
platform	O
.	O
</s>
<s>
Much	O
of	O
this	O
was	O
due	O
to	O
it	O
sharing	O
much	O
of	O
the	O
editor	B-Application
code	O
with	O
Atari	B-Language
BASIC	I-Language
,	O
which	O
had	O
also	O
been	O
written	O
by	O
Shepardson	B-Device
Microsystems	I-Device
.	O
</s>
<s>
Atari	B-Language
BASIC	I-Language
was	O
notorious	O
for	O
the	O
very	O
slow	O
routines	O
used	O
to	O
convert	O
numerical	O
constants	O
in	O
code	O
into	O
an	O
internal	O
representation	O
,	O
which	O
used	O
binary-coded	O
decimal	O
(	O
BCD	O
)	O
routines	O
in	O
the	O
Atari	O
's	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
The	O
debugger	O
,	O
really	O
a	O
monitor	B-General_Concept
,	O
is	O
entered	O
with	O
the	O
BUG	O
command	O
.	O
</s>
<s>
The	O
debugger	O
allows	O
the	O
viewing	O
and	O
changing	O
of	O
registers	B-General_Concept
and	O
memory	O
locations	O
,	O
code	O
tracing	O
,	O
single-step	O
and	O
disassembly	O
.	O
</s>
<s>
Assembler	B-Application
Editor	B-Application
was	O
written	O
by	O
Kathleen	O
O'Brien	O
of	O
Shepardson	B-Device
Microsystems	I-Device
.	O
</s>
<s>
The	O
company	O
had	O
been	O
hired	O
by	O
Atari	O
to	O
help	O
fit	O
Microsoft	O
6502	B-General_Concept
BASIC	O
onto	O
an	O
8KB	O
ROM	B-Device
,	O
something	O
programmers	O
at	O
Atari	O
were	O
struggling	O
with	O
.	O
</s>
<s>
Instead	O
,	O
Bill	O
Wilkinson	O
suggested	O
designing	O
an	O
entirely	O
new	O
version	O
of	O
BASIC	O
,	O
which	O
became	O
Atari	B-Language
BASIC	I-Language
.	O
</s>
<s>
While	O
Atari	B-Language
BASIC	I-Language
was	O
being	O
written	O
,	O
primarily	O
by	O
Paul	O
Laughton	O
,	O
Brien	O
's	O
husband	O
,	O
O'Brien	O
worked	O
on	O
the	O
Assembler	B-Application
Editor	B-Application
.	O
</s>
<s>
It	O
was	O
written	O
by	O
punching	O
codes	O
into	O
a	O
punch	O
tape	O
machine	O
,	O
running	O
the	O
tape	O
through	O
an	O
EPROM	B-General_Concept
burner	O
,	O
and	O
then	O
testing	O
the	O
resulting	O
ROM	B-Device
in	O
an	O
Atari	B-Device
800	I-Device
.	O
</s>
<s>
The	O
cartridge	B-Protocol
was	O
completed	O
before	O
Atari	B-Language
BASIC	I-Language
,	O
and	O
O'Brien	O
spent	O
some	O
time	O
working	O
on	O
portions	O
of	O
that	O
project	O
as	O
well	O
.	O
</s>
<s>
As	O
part	O
of	O
Shepardson	O
's	O
work	O
,	O
a	O
number	O
of	O
common	O
routines	O
were	O
incorporated	O
into	O
the	O
Atari	O
computer	O
's	O
operating	B-General_Concept
system	I-General_Concept
,	O
including	O
the	O
floating	B-Algorithm
point	I-Algorithm
math	I-Algorithm
functions	O
.	O
</s>
<s>
These	O
were	O
written	O
by	O
O'Brien	O
,	O
the	O
first	O
floating	B-Algorithm
point	I-Algorithm
math	I-Algorithm
code	O
she	O
worked	O
on	O
.	O
</s>
<s>
The	O
low	O
performance	O
of	O
key	O
functions	O
affected	O
both	O
Atari	B-Language
BASIC	I-Language
and	O
the	O
Assembler	B-Application
Editor	B-Application
and	O
was	O
a	O
topic	O
that	O
Wilkinson	O
often	O
wrote	O
about	O
.	O
</s>
<s>
The	O
following	O
is	O
6502	B-General_Concept
code	O
for	O
Hello	O
World	O
!	O
</s>
<s>
written	O
for	O
the	O
Assembler	B-Application
Editor	B-Application
:	O
</s>
<s>
These	O
commands	O
can	O
be	O
interactively	O
entered	O
to	O
assemble	B-Application
the	O
code	O
,	O
enter	O
the	O
debugger	O
,	O
run	O
the	O
program	O
,	O
then	O
exit	O
the	O
debugger	O
when	O
it	O
is	O
finished	O
:	O
</s>
<s>
Shortly	O
after	O
Shepardson	O
delivered	O
Assembler	B-Application
Editor	B-Application
and	O
Atari	B-Language
BASIC	I-Language
to	O
Atari	O
,	O
Bob	O
Shepardson	O
,	O
the	O
owner	O
,	O
decided	O
to	O
return	O
to	O
being	O
a	O
one-person	O
company	O
.	O
</s>
<s>
O'Brien	O
,	O
Laughton	O
and	O
Wilkinson	O
formed	O
their	O
own	O
company	O
,	O
Optimized	B-Operating_System
Systems	I-Operating_System
Software	I-Operating_System
(	O
OSS	O
)	O
,	O
to	O
continue	O
development	O
of	O
the	O
Atari	O
products	O
.	O
</s>
<s>
They	O
licensed	O
the	O
original	O
source	O
code	O
for	O
BASIC	O
,	O
Assembler	B-Application
Editor	B-Application
and	O
Atari	B-Operating_System
DOS	I-Operating_System
,	O
which	O
they	O
had	O
collectively	O
written	O
.	O
</s>
<s>
In	O
1981	O
,	O
OSS	O
released	O
an	O
improved	O
version	O
of	O
Assembler	B-Application
Editor	B-Application
,	O
EASMD	O
on	O
floppy	B-Device
disk	I-Device
.	O
</s>
<s>
EASMD	O
was	O
replaced	O
by	O
MAC/65	B-Application
in	O
1982	O
.	O
</s>
<s>
MAC/65	B-Application
was	O
one	O
of	O
the	O
fastest	O
assemblers	B-Application
on	O
the	O
platform	O
.	O
</s>
<s>
Much	O
of	O
the	O
improved	O
performance	O
of	O
MAC/65	B-Application
is	O
the	O
result	O
of	O
tokenizing	O
lines	O
of	O
code	O
as	O
they	O
're	O
entered	O
—	O
at	O
is	O
the	O
case	O
with	O
Atari	B-Language
BASIC	I-Language
—	O
to	O
reduce	O
the	O
amount	O
of	O
work	O
needed	O
at	O
assembly	O
time	O
.	O
</s>
<s>
Assembler	B-Application
Editor	B-Application
continued	O
to	O
be	O
available	O
from	O
Atari	O
,	O
and	O
increased	O
in	O
popularity	O
as	O
the	O
price	O
dropped	O
to	O
in	O
the	O
latter	O
half	O
of	O
the	O
1980s	O
.	O
</s>
