How to use AND to check condition in Assembly language? [duplicate] - if-statement

Question

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Closed 2 years ago.
I'm trying to check even odd in assembly, using a 32-bit NASM, the code is working fine for odd numbers, but for even numbers it is giving output
Even
Odd
Odd
My code is,
section .data
even db "Even", 0xa;
odd db "Odd", 0xa;
lene equ $-even;
leno equ $-odd;
section .text
global _start;
_start:
mov ax, 0x4;
and ax, 1;
jz evenn;
jnz oddd;
jmp outprog;
evenn:
mov eax, 4;
mov ebx, 1;
mov ecx, even;
mov edx, lene;
int 0x80;
oddd:
mov eax, 4;
mov ebx, 1;
mov ecx, odd;
mov edx, leno;
int 0x80;
outprog:
mov eax, 1;
int 0x80;

Answer 1

void fun ( int x )
{
int y;
y=x&1;
if(y==0)
{
show_even();
}
else
{
show_odd();
}
}
is essentially what you are trying to do and you start off in the right direction, but after the show_odd or show_even you need to take separate paths to the end of the function you don't want to go through the second path
Your even path is going through this code:
evenn:
mov eax, 4;
mov ebx, 1;
mov ecx, even;
mov edx, lene;
int 0x80;
oddd:
mov eax, 4;
mov ebx, 1;
mov ecx, odd;
mov edx, leno;
int 0x80;
which prints Even then falls into the code that prints Odd. You want to branch to outprog after printing Even.
The C code above as a model instead of this:
void fun ( int x )
{
int y;
y=x&1;
if(y==0)
{
show_even();
}
show_odd();
}
where odd is always printed no matter what.
And you can optimize this into a single instruction.
jz evenn;
jnz oddd;
jmp outprog;
vs
jnz oddd;
Think through the code execution path.