2020/6/29 COMP1521 20T2 ¡ª Week 04 Weekly Test Questions
Week 04 Weekly Test Questions Test Conditions
These questions must be completed under self-administered exam-like conditions. You must time the test yourself and ensure you comply with the conditions below.
You may complete this test in CSE labs or elsewhere using your own machine.
You may complete this test at any time before Thursday 02 July 21:00.
Weekly tests are designed to act like a past paper – to give you an idea of how well you are progressing in the course, and what you need to work on. Many of the questions in weekly tests are from past final exams.
Once the first hour has finished, you must submit all questions you’ve worked on.
You should then take note of how far you got, which parts you didn’t understand.
You may choose then to keep working and submit test question anytime up to Thursday 02 July 21:00
However the maximum mark for any question you submit after the first hour will be 50%
You may access this language documentation while attempting this test: C quick reference
You may also access manual entries (the man command).
Any violation of the test conditions will results in a mark of zero for the entire weekly test component.
Set up for the test by creating a new directory called test04, changing to this directory, and fetching the provided code by running these commands:
Or, if you’re not working on CSE, you can download the provided code as a zip file or a tar file.
$ mkdir test04
$ cd test04
$ 1521 fetch test04
Test in Progress ¡ª reading time
You have just over 4 minutes left in reading time. You should not write any code.
:
Extract the Exponent of A Float
Reminder: Float Representation
Exercise Description
Your task is to add code to this function in float_exp.c:
The function float_exp is given the bits of a float as type uint32_t. Add code so that it returns the exponent. In other words return the contents of bits 23-30.
This function must be implemented only using bit operations and integer comparisons.
// given the 32 bits of a float return the exponent
uint32_t float_exp(uint32_t f) {
return 42; // REPLACE ME WITH YOUR CODE
}
https://cgi.cse.unsw.edu.au/~cs1521/20T2/test/04/questions 1/4
2020/6/29 COMP1521 20T2 ¡ª Week 04 Weekly Test Questions
Do not remove the bias (subtract 127) from the exponent. Once this functions is completed, you should get output like:
Use make(1) to build your code: Assumptions/Limitations/Clarifications
You may define and call your own functions if you wish. float_exp should return a value between 0 and 255 inclusive.
You are not permitted to call any functions from the C library, or to perform floating-point operations, or to use variables of type float or double, or to use multiplication or division.
You are not permitted to change the main function you have been given, or to change float_exp’ prototype (its return type and argument types).
iff stands for ¡°if and only if¡±.
When you think your program is working you can autotest to run some simple automated tests:
When you are finished working on this exercise you must submit your work by running give:
Reminder: Float Representation
Exercise Description
Your task is to add code to this function in sign_flip.c:
The function sign_flip is given the bits of a float as type uint32_t. Add code so that it changes the sign of the number. If it is positive it should be changed to negative. If it is negative it should be changed to positive.
In other words change (flip) bit 31.
This function must be implemented only using bit operations and integer comparisons. Once this functions is completed, you should get output like:
$ ./float_exp -42
float_exp(-42) returned 0x84
$ ./float_exp 3.14159 float_exp(3.14159012) returned 0x80 $ ./float_exp -inf
float_exp(-inf) returned 0xff
$ make # or ‘make float_exp’
$ 1521 autotest float_exp
$ give cs1521 test04_float_exp float_exp.c
:
Flip the Sign of A Float
// given the 32 bits of a float return it with its sign flipped
uint32_t sign_flip(uint32_t f) {
return 42; // REPLACE ME WITH YOUR CODE
}
$ ./sign_flip -42
sign_flip(-42) returned 42
$ ./sign_flip 3.14159 sign_flip(3.14159012) returned -3.14159012 $ ./sign_flip -2.718 sign_flip(-2.71799994) returned 2.71799994 $ ./sign_flip -inf
sign_flip(-inf) returned inf
Use make(1) to build your code: https://cgi.cse.unsw.edu.au/~cs1521/20T2/test/04/questions
2/4
2020/6/29 COMP1521 20T2 ¡ª Week 04 Weekly Test Questions
Use make(1) to build your code:
$ make # or ‘make sign_flip’
Assumptions/Limitations/Clarifications
You may define and call your own functions if you wish.
You are not permitted to call any functions from the C library, or to perform floating-point operations, or to use variables of type float
or double, or to use multiplication or division.
You are not permitted to change the main function you have been given, or to change sign_flip’ prototype (its return type and
argument types).
iff stands for ¡°if and only if¡±.
When you think your program is working you can autotest to run some simple automated tests: When you are finished working on this exercise you must submit your work by running give:
Download bit_rotate.c, or copy it to your CSE account using the following command:
Your task is to add code to this function in bit_rotate.c:
The function bit_rotate is given an int n and a 16-bit value as type uint16_t. Add code so that it returns the value with its bits rotated left n times.
When rotating a 16-bit value left one position, the value of bit 15 is moved to bit 0, the value of bit 0 to bit 1, the value of 1 to bit 2 … For example:
$ 1521 autotest sign_flip
$ give cs1521 test04_sign_flip sign_flip.c
:
Rotate a 16-bit Value N Positions
$ cp -n /web/cs1521/20T2/activities/bit_rotate/files.cp/bit_rotate.c .
// return the value bits rotated left n_rotations
uint16_t bit_rotate(int n_rotations, uint16_t bits) { return 42; //REPLACE ME WITH YOUR CODE
}
$ ./bit_rotate 5 0x0001
bit_rotate(5, 0x0001) returned 0x0020
$ ./bit_rotate 15 0x0001
bit_rotate(15, 0x0001) returned 0x8000
$ ./bit_rotate 18 0x0001
bit_rotate(18, 0x0001) returned 0x0004
$ ./bit_rotate -3 0x0001
bit_rotate(-3, 0x0001) returned 0x2000
$ ./bit_rotate 8 0x1234
bit_rotate(8, 0x1234) returned 0x3412
$ ./bit_rotate 1 0xbeef
bit_rotate(1, 0xbeef) returned 0x7ddf
$ ./bit_rotate 1000 0xdead bit_rotate(1000, 0xdead) returned 0xadde $ ./bit_rotate -42 0xfeed bit_rotate(-42, 0xfeed) returned 0xbb7f
Assumptions/Limitations/Clarifications
You may define and call your own functions if you wish.
You are not permitted to call any functions from the C library.
You are not permitted to change the main function you have been given, or to change bit_rotate’s prototype (its return type and argument types).
When you think your program is working you can autotest to run some simple automated tests: When you are finished working on this exercise you must submit your work by running give:
$ 1521 autotest bit_rotate
https://cgi.cse.unsw.edu.au/~cs1521/20T2/test/04/questions
3/4
2020/6/29 COMP1521 20T2 ¡ª Week 04 Weekly Test Questions
$ give cs1521 test04_bit_rotate bit_rotate.c
Submission
When you are finished each exercise make sure you submit your work by running give.
You can run give multiple times. Only your last submission will be marked.
Don’t submit any exercises you haven’t attempted.
If you are working at home, you may find it more convenient to upload your work via give’s web interface. Remember you have until Thursday 02 July 21:00 to complete this test.
Automarking will be run by the lecturer several days after the submission deadline for the test, using test cases that you haven’t seen: different to the test cases autotest runs for you.
(Hint: do your own testing as well as running autotest ) Test Marks
After automarking is run by the lecturer you can view it here the resulting mark will also be available via via give’s web interface or by running this command on a CSE machine:
The test exercises for each week are worth in total 1 marks.
The best 6 of your 8 test marks for weeks 3-10 will be summed to give you a mark out of 9.
COMP1521 20T2: Computer Systems Fundamentals is brought to you by the School of Computer Science and Engineering
at the University of New South Wales, Sydney.
For all enquiries, please email the class account at cs1521@cse.unsw.edu.au CRICOS Provider 00098G
$ 1521 classrun -sturec
https://cgi.cse.unsw.edu.au/~cs1521/20T2/test/04/questions
4/4