<s>
FLEX	B-Device
is	O
a	O
discontinued	O
single-tasking	O
operating	B-General_Concept
system	I-General_Concept
developed	O
by	O
Technical	O
Systems	O
Consultants	O
(	O
TSC	O
)	O
of	O
West	O
Lafayette	O
,	O
Indiana	O
,	O
for	O
the	O
Motorola	B-Device
6800	I-Device
in	O
1976	O
.	O
</s>
<s>
The	O
original	O
version	O
was	O
distributed	O
on	O
8	B-Device
"	I-Device
floppy	I-Device
disks	I-Device
;	O
the	O
(	O
smaller	O
)	O
version	O
for	O
5.25	O
"	O
floppies	O
is	O
called	O
mini-Flex	O
.	O
</s>
<s>
It	O
was	O
also	O
later	O
ported	O
to	O
the	O
Motorola	B-Device
6809	I-Device
;	O
that	O
version	O
is	O
called	O
Flex09	O
.	O
</s>
<s>
All	O
versions	O
are	O
text-based	O
and	O
intended	O
for	O
use	O
on	O
display	O
devices	O
ranging	O
from	O
printing	O
terminals	O
like	O
the	O
Teletype	B-Application
Model	I-Application
33	I-Application
ASR	O
to	O
smart	O
terminals	O
.	O
</s>
<s>
FLEX	B-Device
is	O
a	O
disk-based	O
operating	B-General_Concept
system	I-General_Concept
,	O
using	O
256-byte	O
sectors	O
on	O
soft-sectored	O
floppies	O
;	O
the	O
disk	O
structure	O
uses	O
linkage	O
bytes	O
in	O
each	O
sector	O
to	O
indicate	O
the	O
next	O
sector	O
in	O
a	O
file	O
or	O
free	O
list	O
.	O
</s>
<s>
TSC	O
(	O
and	O
others	O
)	O
provide	O
several	O
programming	O
languages	O
including	O
BASIC	O
in	O
two	O
flavors	O
(	O
standard	O
and	O
extended	O
)	O
and	O
a	O
tokenizing	O
version	O
of	O
extended	O
BASIC	O
called	O
Pre-compiled	O
BASIC	O
,	O
FORTH	B-Application
,	O
C	B-Language
,	O
FORTRAN	B-Application
,	O
and	O
PASCAL	B-Application
.	O
</s>
<s>
TSC	O
also	O
wrote	O
a	O
version	O
of	O
FLEX	B-Device
,	O
Smoke	O
Signal	O
DOS	O
,	O
for	O
the	O
California	O
hardware	O
manufacturer	O
Smoke	O
Signal	O
Broadcasting	O
;	O
this	O
version	O
uses	O
forward	O
and	O
reverse	O
linkage	O
bytes	O
in	O
each	O
sector	O
which	O
increase	O
disk	O
reliability	O
at	O
the	O
expense	O
of	O
compatibility	O
and	O
speed	O
.	O
</s>
<s>
Later	O
,	O
TSC	O
introduced	O
the	O
multitasking	B-Operating_System
,	O
multi-user	B-Operating_System
,	O
Unix-like	B-Operating_System
UniFLEX	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
,	O
which	O
requires	O
DMA	B-General_Concept
disk	O
controllers	O
,	O
8	O
"	O
disk	O
,	O
and	O
sold	O
in	O
small	O
numbers	O
.	O
</s>
<s>
Several	O
of	O
the	O
TSC	O
computer	O
languages	O
were	O
ported	O
to	O
UniFLEX	B-Operating_System
.	O
</s>
<s>
During	O
the	O
early	O
1980s	O
,	O
FLEX	B-Device
was	O
offered	O
by	O
Compusense	O
Ltd	O
as	O
an	O
operating	B-General_Concept
system	I-General_Concept
for	O
the	O
6809-based	O
Dragon	B-Device
64	I-Device
home	O
computer	O
.	O
</s>
<s>
The	O
following	O
commands	B-Application
are	O
supported	O
by	O
different	O
versions	O
of	O
the	O
FLEX	B-Device
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
