CS代写 ÿþCSCI-UA.0201-003

ÿþCSCI-UA.0201-003
Computer Systems Organization
Final Exam Spring 2013 Last name: First name:
Notes:

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·ð If you perceive any ambiguity in any of the questions, state your assumptions clearly
·ð Questions vary in difficulty; it is strongly recommended that you do not spend too much
time on any one question.
·ð This exam is open book/notes but no electronic devices.
1. (5 points) Circle the correct answer among the choices given. If you circle more than one answer, you will lose the grade of the corresponding question.
(A) Which of the following has a larger size (in terms of bytes)?
1. pointer to a character 2. pointer to an integer
3. pointer to a float 4. They are all of the same size.
(B) Which of the following data types is not affected by the byte ordering of the machine (i.e. big endian vs little endian)?
1. char 2. int 3. float 4.double
(C) Presenting +5 in signed integer or in IEEE 754 yields the same bit pattern. 1. The above statement is true
2. The above statement is false
3. It depends on whether the machine is 32-bit or 64-bit
4. It depends on whether the machine is big-endian or little endian.
(D) To uniquely identify a connection we need:
1. A socket and a port number 2. Two sockets
3. An IP address and a port number 4. Two IP addresses
(E) Semaphores are needed the most when we have: 1. Several threads not sharing any variables
2. Several threads sharing a lot of variables
3. Several threads sharing read only variables
4. Only single thread and no concurrency
2. (5 points) Consider the following assembly representation of a function foo containing a for loop:
pushl %ebp
movl %esp,%ebp
pushl %ebx
movl 8(%ebp),%ebx
leal 2(%ebx),%edx
xorl %ecx,%ecx
cmpl %ebx,%ecx
jge .L4
leal 5(%ecx,%edx),%edx
leal 3(%ecx),%eax
imull %eax,%edx
incl %ecx
cmpl %ebx,%ecx
jl .L6
movl %edx,%eax
popl %ebx
movl %ebp,%esp
popl %ebp
ret
Fill in the blanks to provide the functionality of the loop:
int foo(int a){
int i;
int result = _____________;
for( ________; ________; i++ )
{ __________________;
__________________;
return result;
3. (8 points) For the following two functions (assume n >= 0):
(a) What does the function fact do?
(b) For which values of n do fact and fact_u2 produce similar results?
(c) What is the minimum modification that we can do to fact_u2 such that it always produces same result as fact?
4. (4 points) For the following C code, indicate how many times  Hello is printed.
5. (8 points) The left part of the following figure shows a heap with the addresses of each word and the content.
·ð The addresses grow from bottom to top
·ð The memory allocator uses an implicit list
·ð Each memory block has a head of 32 bits and a footer of 32 bits
·ð Bits 0 (right most), 1, and 2 of the header (and footer) are as follows:
o Bit 0: 1 means block is allocated, 0 means free
o Bit 1: 1 means previous block is allocated, 0 means free o Bit 2: always 0
·ð The remaining 29 bits indicate the total size of the block, which is multiple of 8. This means you have to add three zeros to right to get the size.
What you need to do is to complete the right size of the Figure which shows the heap just after executing free(0x400b010). Write the content in hexadecimal.

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