Student "edition" found at {csi dot journalspace dot com}.

Maybe I shouldn't have started this blog now, not with everything that's been going on.

Just to finish up on my discussion yesterday, there were some students who were confused with the 32 bit addition we were making.

First they had to add the lower 16 bits of both numbers. There is a possibility that the answer will be larger than 16 bits, or greater than 65535.

Then their answer will reach the 17th bit, that has a value of 65536.

When they add the higher 16 bits of both 32 bit numbers, they will include this bit.

This is where the confusion comes in. Some students, when they add the carry bit, converts it to the decimal value first.

I asked them: when you're adding 65 and 29, and you carry one to the tens place, do you convert that to ten first? No. Same here.

That's just for the first carry flag. When the higher 16 bits are added, it also affects the carry flag. Since this is the 33rd bit, this has a value of 4 billion plus if it is equal to one.

So even if the higher 16 bits has a value at the end of both operations, if the carry flag is 1, then the 32 bits is not the final answer, but it's that plus the 4 billion equivalent.

There was also a bit of confusion on when the carry flag becomes 1 when dealing with decimal operations. If it is larger than the maximum value, then they have to subtract that maximum value to find out what the value is that remains in the lower 16 bits.

Maybe I should show them how it all works out in binary first before showing them the decimal and hexadecimal shortcuts so that they can appreciate it. I could do that for subtraction, which is our next topic before we actually get to how to display the numbers, which might need teaching the stack.

Session 1705 doesn;t listen during the lectures, but scrambles in a panic to understand the topic during exams and exercises. Class dismissed.