<s>
Kronos	O
is	O
an	O
operating	B-General_Concept
system	I-General_Concept
with	O
time-sharing	B-General_Concept
capabilities	O
,	O
written	O
by	O
Control	O
Data	O
Corporation	O
in	O
1971	O
.	O
</s>
<s>
Kronos	O
ran	O
on	O
the	O
60-bit	O
CDC	B-Device
6000	I-Device
series	I-Device
mainframe	B-Architecture
computers	I-Architecture
and	O
their	O
successors	O
.	O
</s>
<s>
CDC	O
replaced	O
Kronos	O
with	O
the	O
NOS	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
in	O
the	O
late	O
1970s	O
,	O
which	O
were	O
succeeded	O
by	O
the	O
NOS/VE	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
in	O
the	O
mid-1980s	O
.	O
</s>
<s>
The	O
MACE	O
operating	B-General_Concept
system	I-General_Concept
and	O
APEX	O
were	O
forerunners	O
to	O
KRONOS	O
.	O
</s>
