<s>
PurifyPlus	B-General_Concept
is	O
a	O
memory	B-General_Concept
debugger	I-General_Concept
program	O
used	O
by	O
software	O
developers	O
to	O
detect	O
memory	O
access	O
errors	O
in	O
programs	O
,	O
especially	O
those	O
written	O
in	O
C	B-Language
or	O
C++	B-Language
.	O
</s>
<s>
It	O
is	O
functionally	O
similar	O
to	O
other	O
memory	B-General_Concept
debuggers	I-General_Concept
,	O
such	O
as	O
Insure++	B-General_Concept
,	O
Valgrind	B-Application
and	O
BoundsChecker	B-General_Concept
.	O
</s>
<s>
PurifyPlus	B-General_Concept
allows	O
dynamic	O
verification	O
,	O
a	O
process	O
by	O
which	O
a	O
program	O
discovers	O
errors	O
that	O
occur	O
when	O
the	O
program	O
runs	O
,	O
much	O
like	O
a	O
debugger	B-Application
.	O
</s>
<s>
Static	O
verification	O
or	O
static	O
code	O
analysis	O
,	O
by	O
contrast	O
,	O
involves	O
detecting	O
errors	O
in	O
the	O
source	O
code	O
without	O
ever	O
compiling	B-Language
or	O
running	O
it	O
,	O
just	O
by	O
discovering	O
logical	O
inconsistencies	O
.	O
</s>
<s>
The	O
type	O
checking	O
by	O
a	O
C	B-Language
compiler	B-Language
is	O
an	O
example	O
of	O
static	O
verification	O
.	O
</s>
<s>
When	O
a	O
program	O
is	O
linked	B-Application
with	O
PurifyPlus	B-General_Concept
,	O
corrected	O
verification	O
code	O
is	O
automatically	O
inserted	O
into	O
the	O
executable	O
by	O
parsing	O
and	O
adding	O
to	O
the	O
object	B-Language
code	I-Language
,	O
including	O
libraries	O
.	O
</s>
<s>
PurifyPlus	B-General_Concept
also	O
detects	O
memory	B-Error_Name
leaks	I-Error_Name
.	O
</s>
<s>
By	O
default	O
,	O
a	O
leak	O
report	O
is	O
generated	O
at	O
program	O
exit	O
but	O
can	O
also	O
be	O
generated	O
by	O
calling	O
the	O
PurifyPlus	B-General_Concept
leak-detection	O
API	O
from	O
within	O
an	O
instrumented	O
application	O
.	O
</s>
<s>
The	O
errors	O
that	O
PurifyPlus	B-General_Concept
discovers	O
include	O
array	O
bounds	O
reads	O
and	O
writes	O
,	O
trying	O
to	O
access	O
unallocated	O
memory	O
,	O
freeing	O
unallocated	O
memory	O
(	O
usually	O
due	O
to	O
freeing	O
the	O
same	O
memory	O
for	O
the	O
second	O
time	O
)	O
,	O
as	O
well	O
as	O
memory	B-Error_Name
leaks	I-Error_Name
(	O
allocated	O
memory	O
with	O
no	O
pointer	O
reference	O
)	O
.	O
</s>
<s>
Hence	O
PurifyPlus	B-General_Concept
helps	O
by	O
detecting	O
these	O
errors	O
and	O
telling	O
the	O
programmer	O
exactly	O
where	O
they	O
occur	O
.	O
</s>
<s>
Because	O
PurifyPlus	B-General_Concept
works	O
by	O
instrumenting	O
all	O
the	O
object	B-Language
code	I-Language
,	O
it	O
detects	O
errors	O
that	O
occur	O
inside	O
of	O
third-party	O
or	O
operating	B-General_Concept
system	I-General_Concept
libraries	O
.	O
</s>
<s>
These	O
errors	O
are	O
often	O
caused	O
by	O
the	O
programmer	O
passing	O
incorrect	O
arguments	O
to	O
the	O
library	O
calls	O
,	O
or	O
by	O
misunderstandings	O
about	O
the	O
protocols	O
for	O
freeing	O
data	B-General_Concept
structures	I-General_Concept
used	O
by	O
the	O
libraries	O
.	O
</s>
<s>
The	O
ability	O
to	O
detect	O
non-fatal	O
errors	O
is	O
a	O
major	O
distinction	O
between	O
PurifyPlus	B-General_Concept
and	O
similar	O
programs	O
from	O
the	O
usual	O
debuggers	B-Application
.	O
</s>
<s>
By	O
contrast	O
,	O
debuggers	B-Application
generally	O
only	O
allow	O
the	O
programmer	O
to	O
quickly	O
find	O
the	O
sources	O
of	O
fatal	O
errors	O
,	O
such	O
as	O
a	O
program	O
crash	O
due	O
to	O
dereferencing	O
a	O
null	O
pointer	O
,	O
but	O
do	O
not	O
help	O
to	O
detect	O
the	O
non-fatal	O
memory	O
errors	O
.	O
</s>
<s>
Debuggers	B-Application
are	O
useful	O
for	O
other	O
things	O
that	O
PurifyPlus	B-General_Concept
is	O
not	O
intended	O
for	O
,	O
such	O
as	O
for	O
stepping	O
through	O
the	O
code	O
line	O
by	O
line	O
or	O
examining	O
the	O
program	O
's	O
memory	O
by	O
hand	O
at	O
a	O
particular	O
moment	O
of	O
execution	O
.	O
</s>
<s>
PurifyPlus	B-General_Concept
also	O
includes	O
other	O
functionality	O
,	O
such	O
as	O
high-performance	O
watchpoints	O
,	O
which	O
are	O
of	O
general	O
use	O
while	O
using	O
a	O
debugger	B-Application
on	O
one	O
's	O
code	O
.	O
</s>
<s>
It	O
is	O
worth	O
noting	O
that	O
using	O
PurifyPlus	B-General_Concept
makes	O
the	O
most	O
sense	O
in	O
programming	O
languages	O
that	O
leave	O
memory	B-General_Concept
management	I-General_Concept
to	O
the	O
programmer	O
.	O
</s>
<s>
Hence	O
,	O
in	O
Java	B-Language
,	O
Lisp	B-Language
,	O
or	O
Visual	B-Language
Basic	I-Language
,	O
for	O
example	O
,	O
automatic	O
memory	B-General_Concept
management	I-General_Concept
reduces	O
occurrence	O
of	O
any	O
memory	B-Error_Name
leaks	I-Error_Name
.	O
</s>
