CSCI-UA.0201-003
Computer Systems Organization
Midterm Exam Fall 2015 (time: 60 minutes)
计算机代考 Which of the following expressions generate correct mask? Circle ALL correct answers. There may be more than one correct answer, or there may be none!
Notes:
- If you perceive any ambiguity in any of the questions, state your assumptions clearly.
- Questions vary in difficulty; it is strongly recommended that you do not spend too much time on any one question.
1.[2 points] What would have happened if we didn’t have linkers? State 2 consequences. 计算机代考
2.[5 points] Fill in the blanks in the following table, assume the instructions are executed sequentially (i.e. instruction 1 executed, then instruction 2, then instruction 3. Assume rax and rbx are holding signed numbers.
3.[5 points] For the following assembly code and its corresponding C code, fill-in the blanks in the C code assuming x will go into %rbx and y will go into %rax;
4.[2 points] Can the carry flag (CF) and the overflow flag (OF) be both 1 at the same time? If yes, give an example of an operation that does this (no need for assembly code, just describe the operation). If not, explain why not.
5.[2 points] State two reasons for why do we need an assembler and not making the compiler generate the binary presentation right away. 计算机代考
6.Suppose x is an integer (i.e. 4 bytes). We want to test whether the most significant bit of x is 1 or not (i.e. the left most bit), so we wrote the expression:
if( (x & mask) != 0)
a.[1 point] What is the value of mask, both in binary and hexadecimal?
b.[2 points] Which of the following expressions generate correct mask? Circle ALL correct answers. There may be more than one correct answer, or there may be none!
- 0x1FFFFFFF << 3
- 0x1FFFFFFF << 2
- two’s complement of 0xFFFFFFFC
- two’s complement of (-2)
c.[1 point] Please give the expression that sets the most significant bit of x to 1 and leave all the other bits unchanged.
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