<s>
Existence	B-General_Concept
checking	I-General_Concept
or	O
existence	B-General_Concept
detection	I-General_Concept
is	O
an	O
important	O
aspect	O
of	O
many	O
computer	B-Application
programs	I-Application
.	O
</s>
<s>
For	O
that	O
reason	O
,	O
most	O
programming	O
language	O
libraries	B-Library
contain	O
a	O
means	O
of	O
checking	O
whether	O
a	O
file	O
exists	O
.	O
</s>
<s>
An	O
existence	O
check	O
can	O
sometimes	O
involve	O
a	O
"	O
brute	B-Algorithm
force	I-Algorithm
"	O
approach	O
of	O
checking	O
all	O
records	O
for	O
a	O
given	O
identifier	O
,	O
as	O
in	O
this	O
Microsoft	B-Application
Excel	I-Application
Visual	B-Language
Basic	I-Language
for	I-Language
Applications	I-Language
code	O
for	O
detecting	O
whether	O
a	O
worksheet	O
exists	O
:	O
</s>
