Hi!

I'm don't need help solving this question, I just need an explenation to why it turns out this way. I'm using machine language to calculate the result of a question. The program I'm using need the numbers to be in hexadecimal 2's complement form. The registers I'm using only hold for 8-bit however so I can't put in 4 digits, I can only put in 2. The question is:

-125-30

I'll solve it this way:

-125= FF83 -30= FFE2

The result should be:

-155=FF65

What's strange is even though I enter only 83 and E2 in my code, I get the result 65. I'm told my code and result is correct, but I'm wondering why FF before each number doesn't seem to be necessary? Why do I get the correct result anyway? Why does the program calculate the correct result even though I haven't put in the full 4 digit numbers?