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CS61C Midterm 2 Spring 03 (Clancy)
Problem 0 (1 point, 1 minute)
Put your login name on each page. Also make sure you have provided the informa-
tion requested on the first page.
Problem 1 (6 points, 15 minutes)
Consider the following three machine instructions, which appear in memory starting at the address 0x00400000.
address (in hex) contents (in hex) 00400000 12080002 00400004 3C11FFFF 00400008 08100004
Part a “Disassemble”the instructions; that is, give an assembly language program segment
that would be translated into the given machine language. You may use numeric
rather than symbolic register names. A list of op codes (Figure A.19 from P&H)
appears at the end of this exam. Handle branches and jumps specially; where you would normally have a label, pro-
vide instead a hexadecimal byte address. For example, you should list a jump t o the
first instruction as j 0x
and represent a branch to the first instruction, say bltz, similarly as
bltz $9,0x
Part b
Your login name: c^ s^6 1 c
For each of the instructionsindicate whether (a)it must have contributed an entry to
the relocation table, (b)it may have contributed an entry to the relocation table, or (c)
it could not have contributed an entry to the relocation table. Briefly explain your answers.
address (in hex) contents (in hex)
00400000
00400004
00400008
12080002
3 CllFFFF
08100004
explanation of why this instruction must have, may have, or could not contribute relocation entry
Your login name: c^ s^6 lc-,
Part c
Give the largest (signed) hexadecimal integer value that k could contain and still produce the output
Briefly explain your answer.
no change after conversion to float
Part d
Give the 4 - byte (single precision) IEEE floating-point representation (in hexadeci-
mal) of your answer to part c. Show how you got your answer.
45
Your login name: c^ s^6 1 c
Problem 3 (7 points, 24 minutes)
Both parts of this question involve code from our solution to lab assignment 9, which appears at the end of this exam.
Part a
Suppose that the output buffer were redefined as follows:
Below, describe clearly what other changes to the code are necessary to accommodate
the smaller buffer (give line numbers of statements to be modified, and say what
modifications are necessary).
buffer: .space 2
Execution traces
Version A
I p r i n t c h k f u l l i n t r p no t E m pt y intDone p r i n t chkfull i n t r p notEmpty intDone p r i n t chkfull i n t r p notEmpty i n t Done p r i n t alldone loop
1 7 1 6 25 3 3. 43 49 # 103 1 0 3 9 1 0 4 7 1 0 6 4
2053 2 0 6 1 2077 2080 2081-inf
Version C
p r i n t 1 chkfull i n t r p not E m p t y intDone p r i n t chkfull p r i n t chkfull i n t r p notEmpty intDone x i n t illdone .oop .ntrp
ntDone OOP
1otEmpty
7 1 6 25 3 3 43 49 59
1 0 3 9 1 0 4 7 1 0 6 5 1 0 6 8 1069- 2044 2053 2 0 6 1 2070 - w
IUUI- 1og-m name: (^) C S ~ ~ C -
p r i n t 1 chkfull 7 i n t r p 1 6 notEmpty 25 intDone 1 0 3 3 p r i n t 1 0 4 3 chkfull 1 0 4 9 i n t r p 1 0 5 4 notEmpty 1 0 6 3 intDone 2 0 7 1 p r i n t 2 0 8 1 chkfull 2 0 8 7 i n t r p 2 0 9 2
intDone 3 1 0 8 p r i n t 3 1 1 8 alldone 3 1 2 1
notEmpty 2 1 0 1
loop 3122-inf
