Intel x86 JUMP quick reference

Getting the sense for jumps and flags has long been a troublesome area for me, especially since the Intel assembler book shows 32 of these, all with similar-sounding names. Looking more closely I found that many of the instructions were synonyms for each other, and in practice the whole gamut is not needed, and in the process found that my copy of Intel's 80386 Programmer's Reference Manual gave an incorrect description for one of the instructions.

So I have grouped these functionally, with all instruction synonyms in the same row.

Instruction Description signed-ness Flags short
jump
opcodes near
jump
opcodes

JO Jump if overflow OF = 1 70 0F 80

JNO Jump if not overflow OF = 0 71 0F 81

JS Jump if sign SF = 1 78 0F 88

JNS Jump if not sign SF = 0 79 0F 89

JE
JZ Jump if equal
Jump if zero ZF = 1 74 0F 84

JNE
JNZ Jump if not equal
Jump if not zero ZF = 0 75 0F 85

JB
JNAE
JC Jump if below
Jump if not above or equal
Jump if carry unsigned CF = 1 72 0F 82

JNB
JAE
JNC Jump if not below
Jump if above or equal
Jump if not carry unsigned CF = 0 73 0F 83

JBE
JNA Jump if below or equal
Jump if not above unsigned CF = 1 or ZF = 1 76 0F 86

JA
JNBE Jump if above
Jump if not below or equal unsigned CF = 0 and ZF = 0 77 0F 87

JL
JNGE Jump if less
Jump if not greater or equal signed SF <> OF 7C 0F 8C

JGE
JNL Jump if greater or equal
Jump if not less signed SF = OF 7D 0F 8D

JLE
JNG Jump if less or equal
Jump if not greater signed ZF = 1 or SF <> OF 7E 0F 8E

JG
JNLE Jump if greater
Jump if not less or equal signed ZF = 0 and SF = OF 7F 0F 8F

JP
JPE Jump if parity
Jump if parity even PF = 1 7A 0F 8A

JNP
JPO Jump if not parity
Jump if parity odd PF = 0 7B 0F 8B

JCXZ
JECXZ Jump if %CX register is 0
Jump if %ECX register is 0 %CX = 0
%ECX = 0 E3

Instruction	Description	signed-ness	Flags	short jump opcodes	near jump opcodes
JO	Jump if overflow		OF = 1	70	0F 80
JNO	Jump if not overflow		OF = 0	71	0F 81
JS	Jump if sign		SF = 1	78	0F 88
JNS	Jump if not sign		SF = 0	79	0F 89
JE JZ	Jump if equal Jump if zero		ZF = 1	74	0F 84
JNE JNZ	Jump if not equal Jump if not zero		ZF = 0	75	0F 85
JB JNAE JC	Jump if below Jump if not above or equal Jump if carry	unsigned	CF = 1	72	0F 82
JNB JAE JNC	Jump if not below Jump if above or equal Jump if not carry	unsigned	CF = 0	73	0F 83
JBE JNA	Jump if below or equal Jump if not above	unsigned	CF = 1 or ZF = 1	76	0F 86
JA JNBE	Jump if above Jump if not below or equal	unsigned	CF = 0 and ZF = 0	77	0F 87
JL JNGE	Jump if less Jump if not greater or equal	signed	SF <> OF	7C	0F 8C
JGE JNL	Jump if greater or equal Jump if not less	signed	SF = OF	7D	0F 8D
JLE JNG	Jump if less or equal Jump if not greater	signed	ZF = 1 or SF <> OF	7E	0F 8E
JG JNLE	Jump if greater Jump if not less or equal	signed	ZF = 0 and SF = OF	7F	0F 8F
JP JPE	Jump if parity Jump if parity even		PF = 1	7A	0F 8A
JNP JPO	Jump if not parity Jump if parity odd		PF = 0	7B	0F 8B
JCXZ JECXZ	Jump if %CX register is 0 Jump if %ECX register is 0		%CX = 0 %ECX = 0	E3

Processor Flags

The x86 processors have a large set of flags that represent the state of the processor, and the jump

CF - carry flag: Set on high-order bit carry or borrow; cleared otherwise
PF - parity flag: Set if low-order eight bits of result contain an even number of "1" bits; cleared otherwise
ZF - zero flags: Set if result is zero; cleared otherwise
SF - sign flag: Set equal to high-order bit of result (0 if positive 1 if negative)
OF - overflow flag: Set if result is too large a positive number or too small a negative number (excluding sign bit) to fit in destination operand; cleared otherwise

Navigate: More Tech Tips