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Assembly Program to Count the Number of 1 Bits in BX

January 15, 2020

This program will calculate the number of 1 bit in BX without changing BX. The basic logic of the program is it copies the BX into AX and takes the AND of 1 with AX if the result is 1 then there is 1 at LSB and if it's 0 then there is 0 at LSB. If it's one then we count it otherwise not. Also, rotate BX by one to check for the next bit. This will loop 16 times.

 In this program, the value I have moved in BX is 0EF0h which means 0000110111110000b so this has 7 ones so the program will output 7 and If you change BX the output will be different according to your number.

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.MODEL SMALL
.STACK 100H
.DATA
.CODE
    MAIN PROC
       
       MOV DX, 0
       MOV BX, 0EF0H
       MOV CX, 16
       LABEL: 
        DEC CX
        MOV AX, BX
        AND AX, 1     
        ROL BX, 1
        CMP AX, 0 
        JG INCREMENT
        CMP CX, 0
        JG LABEL
        JMP END
        
        INCREMENT:
            INC DX
            CMP CX, 0
            JG LABEL 
        
       END:      
       ADD DX, 48
       MOV AH, 2
       INT 21H      
    
    MAIN ENDP
END MAIN

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