<s>
The	O
FLAGS	B-General_Concept
register	I-General_Concept
is	O
the	O
status	B-General_Concept
register	I-General_Concept
that	O
contains	O
the	O
current	O
state	O
of	O
a	O
x86	O
CPU	B-Device
.	O
</s>
<s>
It	O
usually	O
reflects	O
the	O
result	O
of	O
arithmetic	O
operations	O
as	O
well	O
as	O
information	O
about	O
restrictions	O
placed	O
on	O
the	O
CPU	B-Device
operation	O
at	O
the	O
current	O
time	O
.	O
</s>
<s>
Additional	O
status	O
flags	B-General_Concept
may	O
bypass	O
memory	O
mapping	O
and	O
define	O
what	O
action	O
the	O
CPU	B-Device
should	O
take	O
on	O
arithmetic	O
overflow	O
.	O
</s>
<s>
The	O
carry	O
,	O
parity	O
,	O
auxiliary	O
carry	O
(	O
or	O
half	B-Device
carry	I-Device
)	O
,	O
zero	O
and	O
sign	B-Algorithm
flags	I-Algorithm
are	O
included	O
in	O
many	O
architectures	O
.	O
</s>
<s>
In	O
the	O
i286	B-General_Concept
architecture	O
,	O
the	O
register	B-General_Concept
is	O
16	O
bits	O
wide	O
.	O
</s>
<s>
Its	O
successors	O
,	O
the	O
EFLAGS	B-General_Concept
and	O
RFLAGS	B-General_Concept
registers	O
,	O
are	O
32	O
bits	O
and	O
64	O
bits	O
wide	O
,	O
respectively	O
.	O
</s>
<s>
Intel	O
x86	O
FLAGS	B-General_Concept
register	I-General_Concept
Bit	O
#	O
Mask	O
Abbreviation	O
Description	O
Category	O
=	O
1	O
=	O
0	O
FLAGS	B-General_Concept
0	O
0x0001	O
CF	O
Carry	B-Algorithm
flag	I-Algorithm
Status	O
CY(Carry )	O
NC(No Carry )	O
1	O
0x0002	O
Reserved	O
,	O
always	O
1	O
in	O
EFLAGS	B-General_Concept
2	O
0x0004	O
PF	O
Parity	B-General_Concept
flag	I-General_Concept
Status	O
PE(Parity Even )	O
PO(Parity Odd )	O
3	O
0x0008	O
Reserved	O
4	O
0x0010	O
AF	O
Auxiliary	O
Carry	B-Algorithm
flag	I-Algorithm
Status	O
AC(Auxiliary Carry )	O
NA(No Auxiliary Carry )	O
5	O
0x0020	O
Reserved	O
6	O
0x0040	O
ZF	O
Zero	B-Algorithm
flag	I-Algorithm
Status	O
ZR(Zero )	O
NZ(Not Zero )	O
7	O
0x0080	O
SF	O
Sign	B-Algorithm
flag	I-Algorithm
Status	O
NG(Negative )	O
PL(Positive )	O
8	O
0x0100	O
TF	O
Trap	B-General_Concept
flag	I-General_Concept
(	O
single	O
step	O
)	O
Control	O
9	O
0x0200	O
IF	O
Interrupt	B-Device
enable	I-Device
flag	I-Device
Control	O
EI(Enable Interrupt )	O
DI(Disable Interrupt )	O
10	O
0x0400	O
DF	O
Direction	B-Device
flag	I-Device
Control	O
DN(Down )	O
UP(Up )	O
11	O
0x0800	O
OF	O
Overflow	B-Algorithm
flag	I-Algorithm
Status	O
OV(Overflow )	O
NV(Not Overflow )	O
12-13	O
0x3000	O
IOPL	B-Device
I/O	B-Device
privilege	I-Device
level	I-Device
(	O
286+	O
only	O
)	O
,	O
always	O
all-1s	O
on	O
8086	O
and	O
186	B-Device
System	O
14	O
0x4000	O
NT	O
Nested	B-General_Concept
task	I-General_Concept
flag	I-General_Concept
(	O
286+	O
only	O
)	O
,	O
always	O
1	O
on	O
8086	O
and	O
186	B-Device
System	O
15	O
0x8000	O
MD	O
Mode	O
flag	O
(	O
NEC	B-Device
V-series	I-Device
only	O
)	O
,	O
NEC	O
,	O
16-bit	B-Device
V-Series	O
User	O
's	O
Manual	O
,	O
document	O
no	O
.	O
</s>
<s>
U11301E	O
,	O
sep	O
2000	O
,	O
p	O
.	O
186reserved	O
on	O
all	O
Intel	O
CPUs.Always	O
1	O
on	O
8086/186	O
,	O
0	O
on	O
286	B-General_Concept
and	O
later	O
.	O
</s>
<s>
Control	O
(	O
NEC	O
only	O
)	O
Native	O
Mode(186 compatible )	O
(	O
NEC	O
only	O
)	O
Emulation	O
Mode(8080 compatible )	O
EFLAGS	B-General_Concept
16	O
0x0001	O
0000	O
RF	O
Resume	O
flag	O
(	O
386+	O
only	O
)	O
System	O
17	O
0x0002	O
0000	O
VM	O
Virtual	B-Application
8086	I-Application
mode	I-Application
flag	O
(	O
386+	O
only	O
)	O
System	O
18	O
0x0004	O
0000	O
AC	O
Alignment	O
Check	O
(	O
486+	O
,	O
ring	O
3	O
)	O
,	O
SMAP	O
Access	O
Check	O
(	O
Broadwell+	O
,	O
ring	O
0-2	O
)	O
System	O
19	O
0x0008	O
0000	O
VIF	O
Virtual	O
interrupt	B-Device
flag	I-Device
(	O
Pentium+	O
)	O
System	O
20	O
0x0010	O
0000	O
VIP	O
Virtual	O
interrupt	O
pending	O
(	O
Pentium+	O
)	O
System	O
21	O
0x0020	O
0000	O
ID	O
Able	O
to	O
use	O
CPUID	B-Architecture
instruction	O
(	O
Pentium+	O
)	O
System	O
22-29	O
0x3FC0	O
0000	O
Reserved	O
30	O
0x4000	O
0000	O
(	O
none	O
)	O
AES	O
key	O
schedule	O
loaded	O
flagVIA	O
,	O
PadLock	O
Programming	O
Guide	O
,	O
v1.66	O
,	O
Aug	O
4	O
,	O
2005	O
,	O
pp	O
.	O
</s>
<s>
Note	O
:	O
The	O
mask	O
column	O
in	O
the	O
table	O
is	O
the	O
AND	O
bitmask	O
(	O
as	O
hexadecimal	O
value	O
)	O
to	O
query	O
the	O
flag(s )	O
within	O
FLAGS	B-General_Concept
register	I-General_Concept
value	O
.	O
</s>
<s>
All	O
FLAGS	B-General_Concept
registers	I-General_Concept
contain	O
the	O
condition	B-General_Concept
codes	I-General_Concept
,	O
flag	O
bits	O
that	O
let	O
the	O
results	O
of	O
one	O
machine-language	B-Language
instruction	O
affect	O
another	O
instruction	O
.	O
</s>
<s>
Arithmetic	O
and	O
logical	O
instructions	O
set	O
some	O
or	O
all	O
of	O
the	O
flags	B-General_Concept
,	O
and	O
conditional	O
jump	O
instructions	O
take	O
variable	O
action	O
based	O
on	O
the	O
value	O
of	O
certain	O
flags	B-General_Concept
.	O
</s>
<s>
For	O
example	O
,	O
jz	O
(	O
Jump	O
if	O
Zero	O
)	O
,	O
jc	O
(	O
Jump	O
if	O
Carry	O
)	O
,	O
and	O
jo	O
(	O
Jump	O
if	O
Overflow	O
)	O
depend	O
on	O
specific	O
flags	B-General_Concept
.	O
</s>
<s>
Other	O
conditional	O
jumps	O
test	O
combinations	O
of	O
several	O
flags	B-General_Concept
.	O
</s>
<s>
FLAGS	B-General_Concept
registers	I-General_Concept
can	O
be	O
moved	O
from	O
or	O
to	O
the	O
stack	O
.	O
</s>
<s>
This	O
is	O
part	O
of	O
the	O
job	O
of	O
saving	O
and	O
restoring	O
CPU	B-Device
context	O
,	O
against	O
a	O
routine	O
such	O
as	O
an	O
interrupt	O
service	O
routine	O
whose	O
changes	O
to	O
registers	O
should	O
not	O
be	O
seen	O
by	O
the	O
calling	O
code	O
.	O
</s>
<s>
The	O
PUSHF	O
and	O
POPF	O
instructions	O
transfer	O
the	O
16-bit	B-Device
FLAGS	B-General_Concept
register	I-General_Concept
.	O
</s>
<s>
PUSHFD/POPFD	O
(	O
introduced	O
with	O
the	O
i386	B-General_Concept
architecture	O
)	O
transfer	O
the	O
32-bit	O
double	O
register	B-General_Concept
EFLAGS	B-General_Concept
.	O
</s>
<s>
PUSHFQ/POPFQ	O
(	O
introduced	O
with	O
the	O
x64	B-Device
architecture	I-Device
)	O
transfer	O
the	O
64-bit	B-Device
quadword	O
register	B-General_Concept
RFLAGS	B-General_Concept
.	O
</s>
<s>
In	O
64-bit	B-Device
mode	O
,	O
PUSHF/POPF	O
and	O
PUSHFQ/POPFQ	O
are	O
available	O
but	O
PUSHFD/POPFD	O
are	O
not	O
.	O
</s>
<s>
The	O
lower	O
8	O
bits	O
of	O
the	O
FLAGS	B-General_Concept
register	I-General_Concept
is	O
also	O
open	O
to	O
direct	O
load/store	O
manipulation	O
by	O
SAHF	O
and	O
LAHF	O
(	O
load/store	O
AH	O
into	O
flags	B-General_Concept
)	O
.	O
</s>
<s>
The	O
ability	O
to	O
push	O
and	O
pop	O
FLAGS	B-General_Concept
registers	I-General_Concept
lets	O
a	O
program	O
manipulate	O
information	O
in	O
the	O
FLAGS	B-General_Concept
in	O
ways	O
for	O
which	O
machine-language	B-Language
instructions	O
do	O
not	O
exist	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
cld	O
and	O
std	O
instructions	O
clear	O
and	O
set	O
the	O
direction	B-Device
flag	I-Device
(	O
DF	O
)	O
,	O
respectively	O
;	O
but	O
there	O
is	O
no	O
instruction	O
to	O
complement	O
DF	O
.	O
</s>
<s>
This	O
can	O
be	O
achieved	O
with	O
the	O
following	O
assembly	B-Language
code	I-Language
:	O
</s>
<s>
By	O
manipulating	O
the	O
FLAGS	B-General_Concept
register	I-General_Concept
,	O
a	O
program	O
can	O
determine	O
the	O
model	O
of	O
the	O
installed	O
processor	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
alignment	O
flag	O
can	O
only	O
be	O
changed	O
on	O
the	O
486	B-General_Concept
and	O
above	O
.	O
</s>
<s>
If	O
the	O
program	O
tries	O
to	O
modify	O
this	O
flag	O
and	O
senses	O
that	O
the	O
modification	O
did	O
not	O
persist	O
,	O
the	O
processor	O
is	O
earlier	O
than	O
the	O
486	B-General_Concept
.	O
</s>
<s>
Starting	O
with	O
the	O
Intel	B-General_Concept
Pentium	I-General_Concept
,	O
the	O
CPUID	B-Architecture
instruction	O
reports	O
the	O
processor	O
model	O
.	O
</s>
