Operating systems Three Easy Pieces: Chapter 45 solution

Question 1

Sum: 71 Xor: 51 Fletcher: 73 196

Question 3

./checksum.py -D 136,68,34,17 -c

It can happen when there is only one 1 in a position in all the bytes.

Question 4

./checksum.py -D 134,129,1,8 -c

Question 5

Additive checksum will be same for any data set if their summation is same is same. For example

./checksum.py -D 134,129,1,8 -c
./checksum.py -D 131,130,2,9 -c

Question 6

./checksum.py -D 88,145,37,168 -c
./checksum.py -D 216,149,33,40 -c

In general it can happen if bit flip happens in a complementary way in any two of the bytes.

Question 7

Fletcher respects the order of the data unlike the other two.

Question 8

./checksum.py -D 0,1,2,258 -c
./checksum.py -D 0,1,2,3 -c