Answer from cs61c-av (Kenneth Wong 16192104) for Question 4
The cause for undefined results, is if everything is run at the same time, or basically if there is no delay inbetween commands.  In the code above, you set a=0 and b=1 in the first line, and a=1,b=0 in the second line.  But since it is all executed at the same time, a system might get the command a=0, b=0 rather than the lines above.  This could cause unexpected results