Assembly Language Transfer Instruction rule summary

Summary: Although the JMP Directive provides control over transfers, it does not allow any complex judgments to be made. The 80x86 conditional jump instruction provides this kind of judgment. Conditional jump directives are essential elements for creating loops and implementing other conditional execution statements, such as IF...ENDIF. The conditional jump command checks one or more flag bits to determine if they match a particular condition (like the SETCC Directive): If the flag matches successfully, the instruction transfers control to the target location, and if the match fails, the CPU ignores the conditional jump instruction and continues to execute the next instruction . Some conditional jump instructions simply test the setting of the symbol bit (sign), carry bit (carry), overflow bit (overflow), 0 flag (zero) bit. For example, after executing a SH1 instruction, you need to test the carry flag to determine whether the SH1 is shifted from the high address of the operand to one bit. Similarly, you can test the 0 flag bit after a test instruction to determine whether the specified bit is 1. In most cases, the conditional jump instruction is executed after the CMP directive. The CMP directive sets the flag bit to determine less than, greater than, equal to, and so on. JCC directive for test flag bits

Instructions	Description	Conditions	Alias	Opposite instruction
Jc	Jump if the carry bit is set	Carry Flag =1	Jb,jnae	JNC
JNC	Jump if the carry bit has no position	Carry Flag =0	Jnb,jae	Jc
JZ	Jump if the 0 flag is set	0 Mark =1	JE	Jnz
Jnz	If the 0 flag does not have a position then jump	0 Mark =0	JNE	JZ

(Continuation of table)

Instructions	Description	Conditions	Alias	Opposite instruction
Js	Jump if the symbol bit is set	Symbol Mark =1		JNS
JNS	Jump if the symbol bit is not set	Symbol Mark =0		Js
JO	Jump if overflow flag is set	Overflow flag =1		Jno
Jno	If the overflow flag does not have a position then jump	Overflow flag =0	JO
Jp	Jump if parity bit is set	Parity Check Flag =1	JPE	JNP
JPE	Jump if parity bit is parity	Parity Check Flag =1	Jp	JPO
JNP	Jump if parity bit is not set	Parity Check Flag =0	JPO	Jp
JPO	Jump if parity bit is odd check	Parity Check Flag =0	JNP	JPE

JCC Instruction with unsigned number comparison

Instructions	Description	Conditions	Alias	Opposite instruction
JA	If more than (>) jumps	Carry flag =0,0 Flag =0	Jnbe	JNA
Jnbe	Jump if not below or equal to (not <=)	Carry flag =0,0 Flag =0	JA	Jbe
JAE	If it is greater than or equal to (>=), jump	Carry Flag =0	Jnc,jnb	Jnae
JNB	If not below then jump (not <)	Carry Flag =0	Jnc,jae	Jb
Jb	Jump if below (<)	Carry Flag =1	Jc,jnae	JNB
Jnae	Jump if not more than or equal to (not >=)	Carry Flag =1	Jc,jb	JAE
Jbe	Jump if below or equal to (<=)	Carry flag =1 or 0 flag =1	JNA	Jnbe
JNA	Jump if Not over (>)	Carry flag =1 or 0 flag =1	Jbe	JA
JE	Jump if equal (=)	0 Mark =1	JZ	JNE
JNE	If not equal (<>) then jump	0 Mark =0	Jnz	JE

the JCC directive that uses a signed number comparison

Instructions	Description	Conditions	Alias	Opposite instruction
Jg	Jump if greater than (>)	Symbol flag = Overflow flag or 0 flag =0	Jnle	JNG
Jnle	Jump if less than or equal to (<=)	Symbol flag = Overflow flag or 0 flag =0	Jg	Jle
Jge	Jump if greater than or equal to (>=)	Symbol flag = Overflow flag	JNL	Jge
JNL	Jump if not less than (<)	Symbol flag = Overflow flag	Jge	JL
JL	Jump if less than (<)	Symbol Flags <> Overflow flags	Jnge	JNL
Jnge	If greater than or equal to (>=) jump	Symbol Flags <> Overflow flags	JL	Jge
Jle	If less than or equal to (<=) jumps	Symbol sign <> overflow flag or 0 mark =1	JNG	Jnle
JNG	If not greater than (not >) then jump	Symbol sign <> overflow flag or 0 mark =1	Jle	Jg
JE	Jump if equals (=)	0 Mark =1	JZ	JNE
JNE	If not equal to (<>) then jump	0 Mark =0	Jnz	JE

Loop Jump Command: Note the following three lines of code:

1. MOV CX,3
2. Next:movsb
3. LOOP NEXT

Among them, loop's jump mechanism: through the automatic decrement of CX to achieve jump reference: http://blog.csdn.net/trochiluses/article/details/19355425

Assembly Language Transfer Instruction rule summary