<s>
On	O
graphing	B-Application
calculators	I-Application
,	O
an	O
assembly	B-Device
shell	I-Device
is	O
a	O
program	O
that	O
is	O
used	O
to	O
run	O
other	O
programs	O
written	O
in	O
the	O
calculator	O
's	O
native	O
machine	B-Language
code	I-Language
rather	O
than	O
the	O
calculator	O
's	O
standard	O
high-level	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
While	O
all	O
assembly	B-Device
shells	I-Device
can	O
run	O
assembly	O
programs	O
,	O
some	O
can	O
also	O
run	O
high-level	O
programs	O
.	O
</s>
<s>
For	O
example	O
,	O
MirageOS	O
and	O
DoorsCS	O
,	O
two	O
popular	O
TI-83	B-Device
+	O
assembly	B-Device
shells	I-Device
,	O
can	O
run	O
TI-BASIC	B-Language
programs	O
by	O
placing	O
a	O
colon	O
as	O
the	O
first	O
bit	O
of	O
code	O
on	O
the	O
first	O
line	O
in	O
the	O
program	O
.	O
</s>
<s>
Assembly	B-Device
shells	I-Device
were	O
created	O
when	O
calculator	O
manufacturers	O
did	O
not	O
support	O
native-code	O
programming	O
.	O
</s>
<s>
ZShell	O
,	O
the	O
first	O
assembly	B-Device
shell	I-Device
,	O
was	O
created	O
for	O
the	O
TI-85	B-Device
after	O
an	O
exploit	O
was	O
found	O
using	O
a	O
hacked	O
memory	O
backup	O
file	O
containing	O
the	O
shell	B-Operating_System
to	O
bypass	O
the	O
calculator	O
's	O
standard	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Rather	O
than	O
crack	O
down	O
on	O
users	O
who	O
had	O
managed	O
to	O
bypass	O
the	O
OS	O
to	O
run	O
their	O
own	O
code	O
,	O
Texas	O
Instruments	O
chose	O
to	O
release	O
native	O
programming	O
information	O
for	O
its	O
then-upcoming	O
TI-83	B-Device
calculator	O
.	O
</s>
<s>
However	O
,	O
their	O
stance	O
changed	O
and	O
they	O
decided	O
to	O
remove	O
native	B-Language
code	I-Language
functionality	O
from	O
the	O
TI-84	O
plus	O
CE	O
,	O
making	O
an	O
assembly	B-Device
shell	I-Device
necessary	O
once	O
again	O
.	O
</s>
<s>
Although	O
this	O
rendered	O
the	O
traditional	O
assembly	B-Device
shell	I-Device
unnecessary	O
on	O
the	O
TI-83	B-Device
hardware	O
,	O
calculator	O
programmers	O
continued	O
to	O
develop	O
shells	O
to	O
supplement	O
or	O
replace	O
the	O
standard	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Since	O
the	O
TI-83	B-Device
,	O
TI	O
has	O
supported	O
assembly-level	O
programming	O
on	O
all	O
subsequent	O
graphing	B-Application
calculators	I-Application
,	O
though	O
similar	O
shell	B-Operating_System
hacks	O
needed	O
to	O
be	O
created	O
for	O
older	O
hardware	O
,	O
such	O
as	O
the	O
TI-82	O
and	O
the	O
TI-92	O
.	O
</s>
<s>
Hewlett-Packard	O
also	O
supports	O
assembly	O
language	O
programming	O
,	O
though	O
onboard	O
programming	O
tools	O
mean	O
that	O
a	O
separate	O
shell	B-Operating_System
is	O
not	O
needed	O
.	O
</s>
