| 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 conditional jump instructions can key off of them in combination.
- 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
- Reference: http://www.unixwiz.net/techtips/x86-jumps.html
