<s>
The	O
singly	B-Application
rooted	I-Application
hierarchy	I-Application
,	O
in	O
object-oriented	B-Language
programming	I-Language
,	O
is	O
a	O
characteristic	O
of	O
most	O
(	O
but	O
not	O
all	O
)	O
OOP-based	O
programming	O
languages	O
.	O
</s>
<s>
In	O
most	O
such	O
languages	O
,	O
in	O
fact	O
,	O
all	O
classes	O
inherit	B-Language
directly	O
or	O
indirectly	O
from	O
a	O
single	O
root	O
,	O
usually	O
with	O
a	O
name	O
similar	O
to	O
Object	O
;	O
all	O
classes	O
then	O
form	O
a	O
common	O
inheritance	B-Language
hierarchy	I-Language
.	O
</s>
<s>
This	O
idea	O
was	O
introduced	O
first	O
by	O
Smalltalk	B-Application
,	O
and	O
was	O
since	O
used	O
in	O
most	O
other	O
object-oriented	B-Language
languages	I-Language
(	O
notably	O
Java	B-Language
and	O
C#	B-Application
)	O
.	O
</s>
<s>
A	O
notable	O
exception	O
is	O
C++	B-Language
,	O
where	O
(	O
mainly	O
for	O
compatibility	O
with	O
C	O
and	O
efficiency	O
)	O
there	O
is	O
no	O
single	O
object	O
hierarchy	O
.	O
</s>
<s>
Containers	O
in	O
C++	B-Language
have	O
been	O
implemented	O
with	O
multiple	B-Application
inheritance	I-Application
,	O
and	O
with	O
help	O
of	O
template-based	O
generic	B-Language
programming	I-Language
by	O
Bjarne	O
Stroustrup	O
.	O
</s>
<s>
Other	O
object-oriented	B-Language
languages	I-Language
without	O
a	O
singly	B-Application
rooted	I-Application
hierarchy	I-Application
include	O
Objective-C	B-Language
and	O
PHP	B-Application
.	O
</s>
