COMP1521 2020T2 Q2 — Bitwise / data representation

COMP1521 2020T2 Q2 · 10 marks · C Topic: Bitwise / data representation · Source: https://cgi.cse.unsw.edu.au/~cs1521/26T1/resources/practice_exams.html

Summary: Check whether the lowest byte equals the second-lowest byte

Your task is to add code to this function in practice_q2.c :

// given a uint32_t value, // return 1 iff the least significant (bottom) byte // is equal to the 2nd least significant byte; and // return 0 otherwise int practice_q2 ( uint32_t value ) { // PUT YOUR CODE HERE

return 42 ; }

Add code to the function practice_q2 so that, given a uint32_t value, it returns 1 iff the least significant (bottom) byte of value is equal to the second least significant byte. practice_q2 should return 0 otherwise.

For example, given the hexadecimal value 0x12345678 , practice_q2 should return 0 , because the least significant byte, 0x78 , is not equal to the second least significant byte, 0x56 .

Similarly, given the hexadecimal value 0x12345656 , practice_q2 should return 1 , because the least significant byte, 0x56 , is equal to the second least significant byte, 0x56 .

You must use bitwise operators to implement practice_q2 .

For example:

dcc practice_q2.c test_practice_q2.c -o practice_q2 ./practice_q2 0x00000000 practice_q2(0x00000000) returned 1 ./practice_q2 0x00000001 practice_q2(0x00000001) returned 0 ./practice_q2 0x00000100 practice_q2(0x00000100) returned 0 ./practice_q2 0x00000101 practice_q2(0x00000101) returned 1 ./practice_q2 0x00001212 practice_q2(0x00001212) returned 1 ./practice_q2 0x00001213 practice_q2(0x00001213) returned 0 ./practice_q2 0x12345678 practice_q2(0x12345678) returned 0 ./practice_q2 0x12345656 practice_q2(0x12345656) returned 1 ./practice_q2 0x12345634 practice_q2(0x12345634) returned 0 ./practice_q2 0x12345666 practice_q2(0x12345666) returned 0 ./practice_q2 0x12121212 practice_q2(0x12121212) returned 1 ./practice_q2 0x37861212 practice_q2(0x37861212) returned 1 ./practice_q2 0x12121221 practice_q2(0x12121221) returned 0

You can also use make(1) to build your code:

make practice_q2

You are not permitted to call any functions from the C standard library.

You are not permitted to use division ( / ), multiplication ( * ), or modulus ( % ).

You are not permitted to change the main function you have been given.

You are not permitted to change practice_q2 's prototype (its return type and argument types).

No error checking is necessary.

You may define and call your own functions if you wish.

🤖 Online-judge contract (adapted): write a COMPLETE C program. argv[1] is the value (decimal, or 0x-prefixed hex). Print ONLY the integer result followed by a newline. Exit 0.

Examples (input → expected) are shown as sample tests below.