<s>
Zeus	B-Application
Assembler	I-Application
is	O
an	O
assembler	B-Language
development	O
tool	O
for	O
the	O
Z80	B-General_Concept
originally	O
written	O
by	O
Neil	O
Mottershead	O
for	O
the	O
Nascom	O
2	O
and	O
then	O
ported	O
to	O
the	O
ZX	B-Operating_System
Spectrum	I-Operating_System
by	O
Neil	O
Mottershead	O
and	O
Simon	O
Brattel	O
in	O
1983	O
.	O
</s>
<s>
The	O
program	O
was	O
designed	O
to	O
make	O
Z80	B-General_Concept
machine	B-Language
code	I-Language
programming	O
easier	O
,	O
with	O
full	O
symbolic	O
instructions	O
,	O
and	O
an	O
editing	O
style	O
similar	O
to	O
the	O
Spectrum	O
's	O
built-in	O
BASIC	O
.	O
</s>
<s>
Zeus	B-Application
Assembler	I-Application
was	O
later	O
re-released	O
by	O
the	O
manufacturer	O
of	O
the	O
ZX	B-Operating_System
Spectrum	I-Operating_System
,	O
Sinclair	O
Research	O
.	O
</s>
<s>
Zeus	O
is	O
a	O
two-pass	O
assembler	B-Language
which	O
uses	O
the	O
standard	O
Zilog	B-General_Concept
Z80	I-General_Concept
instruction	O
set	O
mnemonics	O
.	O
</s>
<s>
It	O
was	O
the	O
one	O
of	O
the	O
first	O
assemblers	B-Language
to	O
tokenise	O
source	O
code	O
as	O
it	O
is	O
entered	O
,	O
along	O
with	O
MAC/65	B-Application
for	O
the	O
Atari	B-Device
8-bit	I-Device
family	I-Device
,	O
similar	O
to	O
how	O
many	O
BASIC	O
implementations	O
work	O
.	O
</s>
<s>
It	O
has	O
two	O
command	O
modes	O
:	O
assembler	B-Language
and	O
editor	O
,	O
and	O
includes	O
an	O
auto	O
line-numbering	O
facility	O
,	O
and	O
various	O
subroutines	O
for	O
use	O
within	O
the	O
user	O
's	O
programs	O
,	O
as	O
well	O
as	O
printer	O
output	O
and	O
basic	O
assembler	B-Language
features	O
such	O
as	O
labels	O
and	O
expressions	O
.	O
</s>
<s>
The	O
previous	O
year	O
Crystal	O
Computing	O
had	O
released	O
another	O
machine	B-Language
code	I-Language
tool	O
for	O
the	O
16K	O
ZX	B-Operating_System
Spectrum	I-Operating_System
called	O
Monitor	O
and	O
Disassembler	O
that	O
could	O
be	O
used	O
in	O
conjunction	O
with	O
Zeus	O
.	O
</s>
<s>
While	O
Zeus	O
has	O
a	O
monitor	O
included	O
,	O
the	O
more	O
extensive	O
Monitor	O
and	O
Disassembler	O
allows	O
for	O
disassembly	O
,	O
the	O
display	O
and	O
editing	O
of	O
the	O
processor	B-General_Concept
registers	I-General_Concept
,	O
as	O
well	O
as	O
code	O
substitution	O
and	O
the	O
ability	O
to	O
move	O
blocks	O
of	O
memory	O
.	O
</s>
<s>
Zeus	B-Application
Assembler	I-Application
was	O
well-received	O
by	O
the	O
computing	O
press	O
.	O
</s>
<s>
The	O
necessity	O
of	O
exiting	O
the	O
assembler	B-Language
in	O
order	O
to	O
save	O
any	O
generated	O
code	O
was	O
cited	O
as	O
a	O
potential	O
drawback	O
,	O
especially	O
for	O
beginners	O
.	O
</s>
<s>
Sinclair	O
User	O
also	O
praised	O
the	O
documentation	O
as	O
the	O
best	O
of	O
any	O
assembler	B-Language
available	O
at	O
the	O
time	O
,	O
for	O
its	O
use	O
of	O
step-by-step	O
instructions	O
and	O
code	O
examples	O
.	O
</s>
<s>
In	O
2008	O
Simon	O
Brattel	O
rewrote	O
Zeus	O
under	O
the	O
same	O
name	O
as	O
a	O
cross-assembler	O
for	O
Microsoft	O
Windows	O
together	O
with	O
integrated	O
emulator	B-Application
and	O
debugger	B-Application
.	O
</s>
<s>
This	O
was	O
later	O
bundled	O
with	O
various	O
changes	O
to	O
help	O
ZX	B-Device
Spectrum	I-Device
Next	I-Device
developers	O
.	O
</s>
