<s>
IBM	B-Application
Informix	I-Application
C-ISAM	I-Application
(	O
also	O
C-ISAM	B-Application
or	O
cisam	B-Application
)	O
is	O
an	O
X/Open	O
standards-compliant	O
Application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-General_Concept
)	O
to	O
an	O
Indexed	B-Application
Sequential	I-Application
Access	I-Application
Method	I-Application
or	O
ISAM	B-Application
.	O
</s>
<s>
C-ISAM	B-Application
provides	O
the	O
underlying	O
file	O
storage	O
mechanism	O
of	O
the	O
Informix	B-Application
Standard	O
Engine	O
Relational	B-Application
Database	I-Application
Management	I-Application
System	I-Application
(	O
RDBMS	O
)	O
.	O
</s>
<s>
C-ISAM	B-Application
was	O
first	O
created	O
by	O
Informix	B-Application
Corporation	O
in	O
the	O
1980s	O
.	O
</s>
<s>
It	O
provided	O
the	O
underlying	O
file	O
storage	O
mechanism	O
for	O
the	O
popular	O
first	O
generation	O
Informix	B-Application
Relational	B-Application
Database	I-Application
Management	I-Application
System	I-Application
(	O
RDBMS	O
)	O
,	O
which	O
allows	O
data	O
manipulation	O
by	O
way	O
of	O
the	O
Structured	B-Language
Query	I-Language
Language	I-Language
(	O
SQL	B-Language
)	O
protocol	O
.	O
</s>
<s>
This	O
version	O
later	O
became	O
known	O
as	O
the	O
Standard	O
Engine	O
(	O
SE	O
)	O
,	O
to	O
distinguish	O
it	O
from	O
Informix	B-Application
's	O
later	O
database	O
engine	O
which	O
used	O
Random	O
Sequential	O
Access	O
Method	O
(	O
RSAM	O
)	O
.	O
</s>
<s>
Informix	B-Application
initially	O
called	O
this	O
the	O
"	O
Turbo	O
"	O
engine	O
,	O
but	O
that	O
name	O
was	O
later	O
abandoned	O
in	O
favour	O
of	O
the	O
name	O
"	O
OnLine	O
"	O
.	O
</s>
<s>
Many	O
computer	B-General_Concept
systems	I-General_Concept
were	O
written	O
using	O
C-ISAM	B-Application
,	O
which	O
was	O
fast	O
and	O
efficient	O
and	O
flexible	O
,	O
while	O
providing	O
effective	O
mechanisms	O
for	O
maintaining	O
data	O
integrity	O
.	O
</s>
<s>
C-ISAM	B-Application
was	O
also	O
licensed	O
by	O
other	O
software	O
suppliers	O
,	O
for	O
example	O
as	O
the	O
indexed	B-Language
file	I-Language
handler	O
in	O
early	O
versions	O
of	O
Micro	O
Focus	O
COBOL	B-Application
.	O
</s>
<s>
C-ISAM	B-Application
was	O
primarily	O
used	O
for	O
business	O
applications	O
,	O
which	O
were	O
at	O
the	O
time	O
often	O
written	O
in	O
the	O
C	B-Language
language	I-Language
.	O
</s>
<s>
For	O
business	O
purposes	O
,	O
development	O
in	O
a	O
low	O
level	O
3GL	O
such	O
as	O
C	B-Language
could	O
be	O
too	O
slow	O
and	O
error	O
prone	O
,	O
requiring	O
very	O
high	O
skill	O
levels	O
.	O
</s>
<s>
Another	O
significant	O
limitation	O
was	O
in	O
networked	O
applications	O
,	O
since	O
the	O
use	O
of	O
C-ISAM	B-Application
on	O
a	O
client	O
to	O
access	O
a	O
remote	O
file	O
system	O
resulted	O
in	O
heavy	O
network	O
traffic	O
.	O
</s>
<s>
Both	O
problems	O
could	O
be	O
resolved	O
by	O
use	O
of	O
the	O
SE	O
to	O
provide	O
an	O
SQL	B-Language
interface	O
to	O
C-ISAM	B-Application
,	O
using	O
Informix	B-Application
's	O
embedded	B-Language
SQL	I-Language
(	O
ESQL/C	O
and	O
ESQL/COBOL	O
)	O
or	O
4GL	B-Application
products	O
for	O
client	O
development	O
.	O
</s>
<s>
This	O
allowed	O
programmers	B-Application
to	O
focus	O
on	O
business	O
logic	O
,	O
while	O
the	O
compiler	B-Language
and	O
RDBMS	O
took	O
care	O
of	O
error	O
checking	O
and	O
data-type	O
conversion	O
and	O
most	O
importantly	O
,	O
memory	B-General_Concept
management	I-General_Concept
.	O
</s>
<s>
Thus	O
,	O
the	O
direct	O
use	O
of	O
C-ISAM	B-Application
declined	O
,	O
while	O
4GL	B-Application
with	O
embedded	B-Language
SQL	I-Language
,	O
became	O
the	O
new	O
darling	O
of	O
business	O
programmers	B-Application
.	O
</s>
<s>
Competitors	O
like	O
Microsoft	O
and	O
Oracle	B-Application
supplanted	O
these	O
products	O
by	O
vertically	O
integrating	O
theirs	O
,	O
while	O
Informix	B-Application
focused	O
mainly	O
on	O
developing	O
their	O
RDBMS	O
.	O
</s>
<s>
Informix	B-Application
was	O
acquired	O
by	O
IBM	O
in	O
April	O
2001	O
.	O
</s>
<s>
IBM	O
still	O
recommends	O
the	O
use	O
of	O
the	O
Informix	B-Application
Standard	O
Engine	O
for	O
embedded	O
applications	O
.	O
</s>
