<s>
The	O
TI	O
73	O
series	O
is	O
a	O
series	O
of	O
graphing	B-Application
calculators	I-Application
made	O
by	O
Texas	O
Instruments	O
,	O
all	O
of	O
which	O
have	O
identical	O
hardware	O
.	O
</s>
<s>
The	O
original	O
TI-73	B-Device
graphing	B-Application
calculator	I-Application
was	O
originally	O
designed	O
in	O
1998	O
as	O
a	O
replacement	O
for	O
the	O
TI-80	B-Device
for	O
use	O
at	O
a	O
middle	O
school	O
level	O
(	O
grades	O
6-9	O
)	O
.	O
</s>
<s>
Its	O
primary	O
advantage	O
over	O
the	O
TI-80	B-Device
is	O
its	O
512	O
KB	O
of	O
flash	B-Device
memory	I-Device
,	O
which	O
holds	O
the	O
calculator	O
's	O
operating	O
system	O
and	O
thereby	O
allows	O
the	O
calculator	O
to	O
be	O
upgraded	O
.	O
</s>
<s>
Other	O
advantages	O
over	O
the	O
TI-80	B-Device
are	O
the	O
TI-73	B-Device
'	O
s	O
standard	O
sized	O
screen	O
(	O
as	O
opposed	O
to	O
the	O
TI-80	B-Device
'	O
s	O
smaller	O
screen	O
)	O
,	O
the	O
addition	O
of	O
a	O
link	O
port	O
,	O
25	O
KB	O
of	O
RAM	B-Architecture
(	O
as	O
compared	O
to	O
the	O
TI-80	B-Device
'	O
s	O
7	O
KB	O
of	O
RAM	B-Architecture
)	O
,	O
and	O
a	O
faster	O
6	O
MHz	O
Zilog	B-General_Concept
Z80	I-General_Concept
processor	O
(	O
as	O
compared	O
with	O
the	O
TI-80	B-Device
'	O
s	O
980	O
kHz	O
proprietary	O
processor	O
)	O
.	O
</s>
<s>
The	O
TI-73	B-Device
also	O
uses	O
the	O
standard	O
4	O
AAA	B-Algorithm
batteries	I-Algorithm
with	O
a	O
lithium	O
backup	B-Protocol
battery	O
(	O
instead	O
of	O
the	O
TI-80	B-Device
'	O
s	O
2	O
CR2032	O
lithium	O
batteries	O
)	O
.	O
</s>
<s>
In	O
2003	O
,	O
the	O
TI-73	B-Device
was	O
redesigned	O
with	O
a	O
new	O
body	O
shape	O
and	O
redesignated	O
the	O
TI-73	B-Device
Explorer	I-Device
to	O
indicate	O
its	O
currently	O
intended	O
use	O
as	O
a	O
bridge	O
between	O
the	O
TI-15	B-Device
Explorer	I-Device
and	O
similar	O
calculators	O
and	O
the	O
TI-83	B-Device
Plus	I-Device
,	O
TI-84	B-Device
Plus	I-Device
,	O
and	O
similar	O
calculators	O
.	O
</s>
<s>
Later	O
,	O
the	O
TI-73	B-Device
Explorer	I-Device
was	O
remodeled	O
to	O
resemble	O
the	O
TI-84	B-Device
Plus	I-Device
graphing	B-Application
calculator	I-Application
more	O
closely	O
.	O
</s>
<s>
Due	O
to	O
lack	O
of	O
demand	O
in	O
middle	O
schools	O
,	O
the	O
TI-73	B-Device
and	O
TI-73	B-Device
Explorer	I-Device
have	O
not	O
been	O
huge	O
sellers	O
for	O
TI	O
and	O
are	O
not	O
carried	O
by	O
most	O
retail	O
stores	O
.	O
</s>
<s>
Most	O
American	O
upper-level	O
middle	O
school	O
algebra	O
courses	O
generally	O
tend	O
to	O
use	O
the	O
TI-83	B-Device
or	O
TI-84	B-Device
families	O
instead	O
of	O
the	O
TI-73	B-Device
or	O
TI-73	B-Device
Explorer	I-Device
,	O
while	O
most	O
basic	O
middle	O
school	O
math	O
courses	O
generally	O
do	O
not	O
use	O
graphing	B-Application
calculators	I-Application
,	O
instead	O
opting	O
for	O
scientific	O
calculators	O
such	O
as	O
the	O
TI-30	B-Device
or	O
TI-34	B-Device
families	O
.	O
</s>
<s>
Originally	O
the	O
TI-73	B-Device
could	O
only	O
run	O
programs	O
written	O
in	O
TI-BASIC	B-Language
,	O
although	O
that	O
has	O
changed	O
in	O
recent	O
years	O
.	O
</s>
<s>
In	O
2005	O
,	O
an	O
assembly	B-Device
shell	I-Device
called	O
Mallard	O
was	O
released	O
for	O
the	O
TI-73	B-Device
.	O
</s>
<s>
As	O
with	O
the	O
TI-82	O
and	O
the	O
TI-85	O
before	O
,	O
a	O
hacked	O
backup	B-Protocol
file	O
is	O
downloaded	O
containing	O
the	O
assembly	B-Device
shell	I-Device
.	O
</s>
<s>
Released	O
in	O
late	O
2008	O
,	O
the	O
Windows	B-Application
utility	O
Chameleon	O
allows	O
a	O
user	O
to	O
load	O
the	O
TI-73	B-Device
Explorer	I-Device
with	O
a	O
slightly	O
modified	O
TI-83	B-Device
+	I-Device
firmware	O
,	O
giving	O
it	O
nearly	O
equivalent	O
functionality	O
.	O
</s>
<s>
In	O
2009	O
,	O
Texas	O
Instruments	O
updated	O
the	O
skin	O
of	O
the	O
TI-73	B-Device
Explorer	I-Device
to	O
match	O
the	O
shape	O
of	O
the	O
larger	O
TI-84	B-Device
Plus	I-Device
's	O
case	O
.	O
</s>
<s>
The	O
hardware	O
and	O
software	O
remained	O
unchanged	O
and	O
is	O
identical	O
to	O
an	O
older	O
unit	O
wearing	O
the	O
TI-83	B-Device
plus	I-Device
style	O
casing	O
.	O
</s>
