Assembly Language for Beginners

1.14. CONDITIONAL JUMPS

Now let’s reviewthef_signed()function, which works with signed values, in OllyDbg. Flags are set in the
same way: C=1, P=1, A=1, Z=0, S=1, T=0, D=0, O=0. The first conditional jumpJLEis to be triggered:

Figure 1.37:OllyDbg:f_signed(): first conditional jump

In Intel manuals (12.1.4 on page 1013) we find that this instruction is triggered if ZF=1 or SF≠OF. SF≠OF
in our case, so the jump triggers.