assembly language--conditional jump instruction

Modified from: http://bdxnote.blog.163.com/blog/static/84442352015327011988/

In this tribute to the original, most of the online posts are copied from a jump condition to write the wrong post, harm I almost want to suspect life,-_-!.

This post is mainly to change the original author's jump condition to the C language logical expression of the wording, so look more comfortable, and will not produce ambiguity

Direct Transfer Instructions
instruction Format	Machine code	Jump Conditions	Condition Description	symbols
JO OPR	70	Of==1	The result is overflow.
Jno OPR	71	Of==0	Results No overflow
JC OPR	72	Cf==1	Less than	<
JNC OPR	73	Cf==0	Greater than or equal to	>=
Jz/je OPR	74	Zf==1	Result is 0	==
Jnz/jne OPR	75	Zf==0	Results not 0	!=
JS OPR	78	Sf==1	The result is negative	<0
JNS OPR	79	Sf==0	The result is positive	>0
Jp/jpe OPR	7A	Pf==1	The number of 1 in the result is even
Jnp/jpo OPR	7B	Pf==0	The number of 1 in the result is odd

Indirect transfer instruction-unsigned number
instruction Format	Machine code	Test Flags	Condition Description	symbols
Jb/jnae OPR	72	Cf==1	below/not above and not equal to	<
Jnb/jae OPR	73	Cf==0	No less than/above or equal to	>=
Jbe/jna OPR	76	(cf==1) | | (zf==1)	Less than or equal to/not higher than	<=
Jnbe/ja OPR	77	(cf==0) && (zf==0)	No less than and not equal to/above	>

Indirect transfer instruction-signed number
instruction Format	Machine code	Test Flags	Condition Description	symbols
Jl/jnge OPR	7C	(sf^of) ==1	Less than/not greater than and not equal to	<
Jnl/jge OPR	7D	(sf^of) ==0	not less than/greater than or equal to	>=
Jle/jng OPR	7E	(sf^of) ==1 | | (zf==1)	Less than or equal to/not greater than	<=
JNLE/JG OPR	7F	(sf^of) ==0 && (zf==0)	Not less than and not equal to/greater than	>

Understanding Method :
N:not
E:equal
A:above
B:below
L:less (Little's comparative level)
G:greater (comparative level of great)

Conditional jump instruction is to jump according to the value of the relevant flag bit in the flag register, therefore, the conditional jump instruction can only be used with the instruction that can affect the flags of the flag register;
Directives that can directly affect the flag register are:
1. Arithmetic operation instruction: Add, Sub, ADC, SBB, Inc, Dec, neg, mul, Div, Imul, idiv, etc.;
2, bitwise logical operation: And, OR, XOR, not, and so on;
3. Comparison operation instruction: CMP, test;
4. Shift Operation instruction: SHR, SHL, SAR, Sal, Ror, Rol, RCR, RCL;
5, BCD number adjustment directive: AAA, AAs, DAA, Das, AAM, AAD;
6, marking processing instructions: CLC, STC, CMC, CLD, STD, CLI, STI;

The following paragraph is not verified, after the completion of the Assembly to test the paragraph

The sequence of instructions that can indirectly affect the relevant flag bits of the flag register are:
PUSHF--pop eax--Modify EAX--push eax--Popf
That
Pushf
Pop eax
Modify EAX
Push EAX
Popf
Jbe OPR
After such a series of operations, the conditional transfer instruction "Jbe OPR" can also be transferred according to the flag register;

assembly language--conditional jump instruction