8086 Assembly with AFD error but emu8086 everything fine why?

Question

When I'm running this code in emu8086 everything is fine, but I have to run this code in AFD and when then line after line im tipping I have a error in JC et2

Symbol not defined

MOV CL,00fh
MOV SI,000h
MOV DI,000h

;i=0    
MOV [220h+SI],240h

et1:        
MOV AH,[210h+DI]
INC DI
MOV AL, [210h+DI]  
CMP AH,AL
JC et2   

INC SI
INC SI              
MOV [220h+SI],240h

loop et1 

HLT    

et2:      
INC SI
INC SI
DEC CL
JNZ et1
HLT     
loop et2  

ret

Please help me handle that

Answer 1

It seems very hard to find info about "AFD" but here are some pointers that might help you find a solution:

• If you're submitting this program to "AFD" as source, then it could be that the mnemonic jc is simply not understood. Try using jb which does exactly the same.

• Different programs have different sets of reserved words. Maybe "AFD" considers et2 a reserved symbol rendering the instruction jc et2 meaningless. Try renaming your labels. Perhaps choose IsBelow ? Anyway , using more meaningful names is always a good idea.

---

A few remarks on your code:

• You only initialize the CL register with MOV CL,00fh . Note that the loop instruction depends on the entire CX register.

• The loop et2 instruction below the hlt makes no sense! If it got executed at all, it would start a 64KB loop (because the counter would be 0 at that time) destroying your program data altogether.

---

Since all that you really do when AH is below AL is bypass the writing of another number 0240h, you can nicely simplify your progran like this:

    MOV  CX, 000Fh
    MOV  SI, 0000h
    MOV  DI, 0000h
    MOV  [0220h+SI], 0240h
TopOfTheLoop:
    MOV  AH, [0210h+DI]
    INC  DI
    MOV  AL, [0210h+DI]
    INC  SI
    INC  SI
    CMP  AH, AL
    JB   IsBelow
    MOV  [0220h+SI], 0240h
IsBelow:
    LOOP TopOfTheLoop
    HLT    

Answer 2

Yes, to solve my problem you have to define et2:...loop et2 and then write JC et2. if et2 is not defined you cannot use JC et2.