关于汇编语言条件选择

Question

我对c语言更加熟悉，但我们如何将以下c语言编码写入汇编语言？我试过但总是失败。

if(a==4) 
{ 
    routine1(); 
} 
else if(a==5) 
{ 
    routine2(); 
} 
else if(a==6) 
{ 
    routine3(); 
} 

Answer 1

一种可能性是使用goto重写它，那么它应该是直截了当地移植到你使用任何语言汇编。

if (a != 4) goto not4; 
routine1(); 
goto end; 

not4: if (a != 5) goto not5; 
routine2(); 
goto end; 

not5: if (a != 6) goto not6; 
routine3(); 
end: 

Answer 2

在86它会是这样的命令http://www.gabrielececchetti.it/Teaching/CalcolatoriElettronici/Docs/i8086_instruction_set.pdf

a100 
mov al, 0500;move whats in memory location 0500 to al register 
mov bl,4; mov 4 into bl register 
cmp al,bl;this compares them basically subtracting them so 0 is equal 
jz label1;the label is another memory location that you would jump to if they are equal 
mov bl,5; if it doesnt jump then the code will continue to run 
cmp al,bl 
jz label2 
mov bl,6 
cmp al,bl 
jz label3 
int 3; to end program or you can use ret 

的深度描述也检查出的链接...

label1 call 0200;call instruction runs the code that is at the memory location stated 
label2 call 0300 
label3 call 0400 

希望这有助于记住这个是x86！ 快乐编码！