Assembly Language for Beginners

1.19. FLOATING-POINT UNIT JPEtriggered,FLDloads the value ofb(3.4) inST(0): Figure 1.71:OllyDbg: the secondFLDhas been executed ...

1.19. FLOATING-POINT UNIT Second OllyDbg example: a=5.6 and b=-4 Let’s load example into OllyDbg: Figure 1.72:OllyDbg: firstFLDe ...

1.19. FLOATING-POINT UNIT FCOMPexecuted: Figure 1.73:OllyDbg:FCOMPexecuted We see the state of theFPU’s condition flags: all zer ...

1.19. FLOATING-POINT UNIT FNSTSWexecuted: Figure 1.74:OllyDbg:FNSTSWexecuted We see that theAXregister contains0x100: theC0flag ...

1.19. FLOATING-POINT UNIT TESTexecuted: Figure 1.75:OllyDbg:TESTexecuted ThePFflag is cleared. Indeed: the count of bits set in0 ...

1.19. FLOATING-POINT UNIT JPEhasn’t been triggered, soFLDloads the value ofa(5.6) inST(0): Figure 1.76:OllyDbg: secondFLDexecute ...

1.19. FLOATING-POINT UNIT ; leave (_b) on top fstp ST(0) ; current stack state: ST(0) = _b ret 0 _d_max ENDP FCOMdiffers fromFCO ...

1.19. FLOATING-POINT UNIT First OllyDbg example: a=1.2 and b=3.4 BothFLDare executed: Figure 1.77:OllyDbg: bothFLDare executed F ...

1.19. FLOATING-POINT UNIT FCOMhas been executed: Figure 1.78:OllyDbg:FCOMhas been executed C0is set, all other condition flags a ...

1.19. FLOATING-POINT UNIT FNSTSWhas been executed,AX=0x3100: Figure 1.79:OllyDbg:FNSTSWis executed ...

1.19. FLOATING-POINT UNIT TESTis executed: Figure 1.80:OllyDbg:TESTis executed ZF=0, conditional jump is about to trigger now. ...

1.19. FLOATING-POINT UNIT FSTP ST(orFSTP ST(0)) has been executed —1.2 has been popped from the stack, and 3.4 was left on top: ...

1.19. FLOATING-POINT UNIT Second OllyDbg example: a=5.6 and b=-4 BothFLDare executed: Figure 1.82:OllyDbg: bothFLDare executed F ...

1.19. FLOATING-POINT UNIT FCOMhas been executed: Figure 1.83:OllyDbg:FCOMis finished All conditional flags are cleared. ...

1.19. FLOATING-POINT UNIT FNSTSWdone,AX=0x3000: Figure 1.84:OllyDbg:FNSTSWhas been executed ...

1.19. FLOATING-POINT UNIT TESThas been executed: Figure 1.85:OllyDbg:TESThas been executed ZF=1, jump will not happen now. ...

1.19. FLOATING-POINT UNIT FSTP ST(1)has been executed: a value of 5.6 is now at the top of the FPU stack. Figure 1.86:OllyDbg:FS ...

1.19. FLOATING-POINT UNIT mov dword ptr [ebp+b], eax mov eax, [ebp+b_second_half] mov dword ptr [ebp+b+4], eax ; load a and b to ...

1.19. FLOATING-POINT UNIT And ifa=b, then:ZF=1, PF=0, CF=0. Depending on the CPU flags and conditions,SETNBEstores 1 or 0 to A ...

1.19. FLOATING-POINT UNIT Thereby, the conditional jumps instructions listed here can be used after aFNSTSW/SAHFinstruction pair ...