Operacinės Sistemos

2025-02-17 susitinkame per Teams.

Konspektas
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