Counting the number of zeros in a binary representation using assembly language?
Hi
Could anyone suggest how can I count the number of zeros found in a binary representation using assembly language.
For example if the user inputs
20
The output should be
30
Since 20 – 00..010100 (using 32 bits) and contains a total number of 30 zeros.
Thank you
Shifting a register left with the SHL instruction pushes the most significant bit into the carry flag. Therefore, if a 1 was the most significant bit and its shifted left, the carry flag is set, if the most significant bit was 0 it wont be set.
Write a loop that shifts the register you have your input number in to the left 32 times. In this loop have a JC (jump if carry is set / jump no carry) instruction to jump over an instruction where you increment a register containing the sum of your zeros. Heres an untested code snippet:
xor ebx,ebx
mov ecx,32
shiftl:
shl eax,1
jc $+2
inc ebx
loop shiftl
EBX would now contain the number of zeros in the value contained within EAX. Keep in mind that in order to display the number of zeros you will have to convert the value in EBX to to ascii.
Upfront CFD for the Drilling Industry – tricone bit assembly
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