counting number of zeros and ones in a byte

Question

I previously posted a program to find the total number of 1s in a byte. Now I am trying to find the number of 0s in a byte. Following is my code:

MOV AL,1
MOV CX         


        

Answer 1

The bit which is shifted-out from AL goes to the carry-flag, not to the zero-flag. Change your conditional jumps:

    MOV AL,1     ; An investigated byte.    
    MOV CX,08H   ; Number of bits in the byte. 
    MOV BX,0000H ; Result: number of 1s.
    MOV DX,0000H ; Result: number of 0s.
Zero:SHR AL,01H  ; Shift the byte, least significant bit to CF.
    JNC ZrO
ero:INC BX      ; Count 1s. 
    JMP Skip
ZrO:INC DX      ; Count 0s.
Skip:LOOP Zero   ; Repeat CX times.
    hlt

BTW there is a specialized instruction for this task on new Intel processors (NEHALEM): https://www.felixcloutier.com/x86/popcnt

    MOV AL,1     ; An investigated byte.  
    XOR AH,AH    
    POPCNT BX,AX ; Count the number of 1s in AX and put result to BX.
    MOV DX,8
    SUB DX,BX    ; The number of 0s in AL is 8-BX.