zf

[santa]

How can I check if zero flag is set ? Which bit ?

respect  :8)

[P1]

Santa,

There is an op code that does all the work for you.

jz Target ( or jnz )
.
.
.
Target:

Regards,  P1  :8)

[santa]

I konw that, but the thing is that I need check a bit which is responsible for setting ZF

:wink

[P1]

In QEditor there is an OPCODES help file.  This is clipped from there.

FLAGS - Intel 8086 Family Flags Register

      |11|10|F|E|D|C|B|A|9|8|7|6|5|4|3|2|1|0|
        |  | | | | | | | | | | | | | | | | '---  CF Carry Flag
        |  | | | | | | | | | | | | | | | '---  1
        |  | | | | | | | | | | | | | | '---  PF Parity Flag
        |  | | | | | | | | | | | | | '---  0
        |  | | | | | | | | | | | | '---  AF Auxiliary Flag

        |  | | | | | | | | | | | '---  0
        |  | | | | | | | | | | '---  ZF Zero Flag
        |  | | | | | | | | | '---  SF Sign Flag
        |  | | | | | | | | '---  TF Trap Flag  (Single Step)
        |  | | | | | | | '---  IF Interrupt Flag
        |  | | | | | | '---  DF Direction Flag
        |  | | | | | '---  OF Overflow flag
        |  | | | '-----  IOPL I/O Privilege Level  (286+ only)
        |  | | '-----  NT Nested Task Flag  (286+ only)

        |  | '-----  0
        |  '-----  RF Resume Flag (386+ only)
        '------  VM  Virtual Mode Flag (386+ only)
        - see   PUSHF  POPF  STI  CLI  STD  CLD

Regards,  P1  :8)

[donkey]

As P1's chart demonstrates it is bit 6 however using BitTest (BT) you will still have to perform a conditional jump based on the result, in effect you are only copying the Zero flag (ZF) into the Carry flag (CF)

Code Select Expand

pushfd
pop eax
bt eax,6
jnc @F
; bit is set

@@:
; bit is not set

Alot of extra work to replace

Code Select Expand

jnz @F

[P1]

Santa,

What is it your doing???  It would help in giving you an answer, that more directed at what your doing.

Regards,  P1  :8)

[santa]

Hi Hi

P1 .....  it's a secret  :8) but your explanation is sufficient. I have forgotten the bassis of asm ... he he ... I know it's not funny

respect

[P1]

it's a secret  :8)

Just a quick reminder, Please observe all MASMforum rules and guidelines.

Playing with flags is not normal programming.  Has been used for cracks and hacks to work around logic flow of other programs.

Regards,  P1  :8)

[Mark Jones]

Ho Ho Ho!

Those who believe in cracking programs - have never written any.

[santa]

 :clap:

Don't be ridiculous, Please. I've just asked a simple question about asm. I know rules !

it's a secret - he he he ... joke

[evlncrn8]

Ho Ho Ho!

Those who believe in cracking programs - have never written any.

i beg to differ