题目
题目

4520_COMP_SCI_X_0005 Week 8 Exam

匹配题

Category: VM Expressions ~a & ~b Select 5 lines of Hack VM Language, in the order they must be executed, that will implement the Jack expression: ~a & ~b Notes: The expression must be evaluated left to right. The variables a and b are in the local segment at offsets 4 and 5. 1: 1 2: 2 3: 3 4: 4 5: 5

选项
A.sub
B.push local 5
C.neg
D.pop local 6
E.pop a
F.push a
G.push c
H.return
I.lt
J.gt
K.and
L.push local 4
M.pop local 4
N.pop c
O.pop b
P.pop local 5
Q.not
R.push b
S.or
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标准答案
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思路分析
The problem asks you to implement the Hack VM expression ~a & ~b in left-to-right order, where a and b reside in the local segment at offsets 4 and 5, respectively. The correct sequence must load a, negate it, load b, negate it, and then combine the two results with a logical and. Option by option analysis: - sub: This is a subtraction operation, not relevant to computing bitwise negation or a logical and. It would not contribute to evaluating ~a or ~b, so it’s incorrect. - push local 5: This pushes the value of b onto the stack. On its own it does not negate b or combine it with a, so alone it’s insufficient and misplaced in the required left-to-right evaluation. It should appear after pushing and negating a, not by itself as the first step. - neg: This performs arithmetic negation (unary minus), not bitwise N......Login to view full explanation

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