______________________________ Your Name (first last) ______________________________ ← Name of person on left (or aisle) UC Berkeley Fall 2018 CS61C Quest ______________________________ SID ______________________________ Name of person on right (or aisle) → Q1a) With 3 bits , how do we represent 2 ? If it can’t be done, select “ N/A ”. (Select ONE per row) 000 001 010 011 100 101 110 111 N/A Unsigned ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Sign/Magnitude ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ One’s Complement ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Two’s Complement ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Bias; use bias of (2 N1 1) from lecture ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ...scratch space below... Q1b) Convert 26 10 to the following bases (and remove any leading zeros) Binary Hex 0b 0x Q1c) Add these Two’s Complement nibbles: 1001 + 1011 Does it overflow a nibble? (Select ONE) ◯ Yes ◯ No int mystery (unsigned int N) { unsigned int counter = 0; while (N > 0) { counter += N & 1; N = N >> 1; } return counter == 1; } Q2a) What does the mystery return? (Select ONE) ◯ The number of 1s in the binary representation of N ◯ 1 if N is odd, otherwise 0 ◯ 1 if N is a power of 2, otherwise 0 ◯ 1 if the binary representation of N is all 1s, otherwise 0 ◯ 1 if the binary representation of N has any 1s, otherwise 0 Q2b) Given this setup to mystery : unsigned int myN = GetNFromUser(); int mysteryReturn = mystery(myN); ...could myN be changed by the call to mystery ? (Select ONE) ◯ Yes ◯ It depends on the value of myN ◯ No // My project partner wrote this code to duplicate some elements of orig into copy int orig[] = {1,2,3,4,5,6,7,8}; // ints are 4 bytes wide ...scratch space below... int main() { int *backup, *copy, **copyH; backup = copy = (int *) malloc (sizeof(int) * 100); copyH = © for (int i = 0; i < 2; i++) { *copy = orig[i]; *copyH = *copyH + 4; } } Q3a) Right before the for loop, where in memory do the following point ? (Select ONE per row) Code Static Stack Heap orig ◯ ◯ ◯ ◯ backup ◯ ◯ ◯ ◯ copyH ◯ ◯ ◯ ◯ Q3b) Right after the for loop, what is the value of the following? If it’d be garbage, write “ G ”. backup[0] backup[1] copy[0] copy[1] Q4a) Which RISCV snippet could be the compilation of the C code: x15 = 20 ‑ x5 ? (Select ALL that apply ) Assume the C variables x5 and x15 map directly to the registers of the same name. ▢ sub x5, 20, x15 ▢ sub x15, 20, x5 ▢ addi x15, x0, 20 sub x15, x15, x5 ▢ addi x15, x5, ‑20 sub x15, x0, x15 Q4b) Say we have an int array A[99] starting at address 0x00010000 , and register x5 contains &A[0] . Assuming sizeof(int) == 4 , what value is in register x10 after lw x10, 8(x5) ? (Select ALL that apply ) ▢ A[2] ▢ A[8] ▢ &A[2] ▢ &A[8] ▢ 0x00010008 ▢ 0x00080000
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