Disclaimer: This article is a blogger original article, 2019-08-23,22: 21:42 reprint please attach the original source link and this statement.
By ----- drowning heart of the ups and downs ---- blog Park
1, write the assembly instructions only affect the value of CF bit (does not affect other flag
MOV AX,0xFF00
ADD AX,0x0101
2, write assembler instruction only affects the value of the PF position (not affect other flags)
MOV AX,0x3
ADD AX,0xC
3, write assembler instruction only affects the value of the AF bit (does not affect other flags)
MOV AX,0xF0
ADD AX,0x10
Disclaimer: This article is a blogger original article, 2019-08-23,22: 21:42 reprint please attach the original source link and this statement.
By ----- drowning heart of the ups and downs ---- blog Park
4, assembler instruction is written only affect the value of SF-bit (not affect other flag bits)
MOV AX,0x8000
ADD AX,0x1
6, write assembler instruction only affects the value OF-bit (can not affect other flags)
O bits, think, if two positive numbers together (i.e., a number between 0x00 ~ 0x7f), so that it becomes a negative number, the value of these two numbers together 0x7F bound to cross this line, Sign Flag changes will inevitably lead, AF bit byte into bits also occurs, so that the AF bits will change, it is clear, so that between two positive (i.e., 0x00 ~ 0x7f) number of added not, from another angle , then the situation by adding two negative numbers it (0x80 ~ 0xFF) it is not it will make C-bit overflows it, is it, then how to solve this problem, we can use the computer bigger negative number, subtract a positive number .
MOV AL, 0x80
SUB AL,0x10
Disclaimer: This article is a blogger original article, 2019-08-23,22: 21:42 reprint please attach the original source link and this statement.
By ----- drowning heart of the ups and downs ---- blog Park