Mock Interview: Coding random 'Bit masking' Questions | Embedded systems podcast, in Pyjama

𝗜𝗻 𝘁𝗵𝗶𝘀 𝘃𝗶𝗱𝗲𝗼: Mahmad was asked to solve two coding problems.

Questions:

𝗖𝗵𝗮𝗽𝘁𝗲𝗿𝘀:
00:00 Modify a range of bits of a given 32-bit register.
24:12 Minimum number of bit flips required to convert a number A into B.

𝙋𝙖𝙣𝙚𝙡 𝙈𝙚𝙢𝙚𝙗𝙚𝙧𝙨:

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#inpyjama #embeddedsystems #embedded #systemdesign #software #softwareengineering #embeddedpodcast

[yogeshchauhan]

I will give you awesome trick to remember XOR. XOR is nothing but an Inequality detector. When two bits are not equal the XOR operator detect it otherwise not. Conversly, You can remember XNOR as an Equality detector.

[sushilsingh]

Valuable content, the likes of which have been missing specially for embedded domain. Please do keep with such content in future as well😊.

[emanivamsikrishna]

Thank you guys for such a detailed explanation. Honestly, I did not know about builtin function like popcount that's supported by GCC compiler. Figured out there are couple of more functions like this while I goggled about the same.

[tabrezahmed]

This is Quality content !! Thanks for doing this!

[poornachandumarneni]

Guys it’s a great series, we know that u people are attempting with any preparation, please continue the series & we need more questions in bit masking

[Akash_]

last problem
int num = a^b;
for(int i=0;i<8*sizeof(a);i++)
{
flag = ((num>>i) & 1)?1:0;
if(flag)
{
count++;
}
}
printf("number of bits: %d", count);

Please continue this series..Thanku!!!

[bornmad]

I think in first question where you have calculated "value to be written", we don't need mask. It can simply be x << m because x is smaller than 2^(n-m). Please correct me if I am wrong. But yes we need mask for putting that value in a.

[JgNt]

Why a and b are multiplied with 0x01 in line ax01 & bx01? To get the rightmost bit?

[shankarsridhar]

We can also generate mask programmatically by doing 2^(m-n+1) to get a mask of 8 bits, OR it with desired value and then << m-1 for final mask, then OR it with input to set those bit range. Am I correct?

[poornachandumarneni]

Need more info & questions on bit masking