Computer Systems: Program... -Access
3rd Edition
ISBN: 9780134071923
Author: Bryant
Publisher: PEARSON
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Textbook Question
Chapter 2, Problem 2.66HW
Write code to implement the following function:
/*
* Generate mask indicating leftmost 1 in x. Assume w=32.
* For example, 0xFF00 -> 0x8000, and 0x6600 — > 0x4000.
* If x = 0, then return 0.
*/
int leftmost_one(unsigned x);
Your function should follow the bit-level integer coding rules (page 128), except that you may assume that data type int has w = 32 bits.
Your code should contain a total of at most 15 arithmetic, bitwise, and logical operations.
Hint: First transform x into a bit
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implement greatestBitPos function Compute a mask marking the most significant 1 bit.
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/* * greatestBitPos - return a mask that marks the position of the* most significant 1 bit. If x == 0, return 0* Example: greatestBitPos(96) = 0x40* Legal ops: ! ~ & ^ | + << >>* Max ops: 70* Rating: 4 */int greatestBitPos(int x) {return 2;}
Implement the function (in C or C++) with the following prototype:
/** Implement a function which rotates a word left by n-bits, and returns that rotated value. Assume 0 <= n < w Examples: when x = 0x12345678 and w = 32: n=4 -> 0x23456781 n=20 -> 0x67812345 */ unsigned rotate_left(unsigned x, int n);
The function should follow the bit-level integer coding rules above. Be careful of the case n = 0.
Suppose we number the bytes in a w-bit word from 0 (least significant) to w/8 – 1 (most significant). Write code for the following C function, which will return an unsigned value in which byte i of argument x has been replaced by byte b:
unsigned replace_byte (unsigned x, int i, unsigned char b);
Here are some examples showing how the function should work:
replace_byte(0x12345678, 2, 0xAB) --> 0x12AB5678
replace_byte(0x12345678, 0, 0xAB) --> 0x123456AB
Bit-Level Integer Coding Rules
In several of the following problems, we will artificially restrict what programming constructs you can use to help you gain a better understanding of the bit-level, logic, and arithmetic operations of C. In answering these problems, your code must follow these rules:
Allowed operations
All bit-level and logic operations.
Left and right shifts, but only with shift amounts between 0 and w – 1.
Addition and subtraction.
Equality (==) and inequality (!=) tests. (Some of the problems do not allow…
Chapter 2 Solutions
Computer Systems: Program... -Access
Ch. 2.1 - Practice Problem 2.1 (solution page 143) Perform...Ch. 2.1 - Prob. 2.2PPCh. 2.1 - Prob. 2.3PPCh. 2.1 - Practice Problem 2.4 (solution page 144) Without...Ch. 2.1 - Prob. 2.5PPCh. 2.1 - Prob. 2.6PPCh. 2.1 - Prob. 2.7PPCh. 2.1 - Prob. 2.8PPCh. 2.1 - Practice Problem 2.9 solution page 146 Computers...Ch. 2.1 - Prob. 2.10PP
Ch. 2.1 - Prob. 2.11PPCh. 2.1 - Prob. 2.12PPCh. 2.1 - Prob. 2.13PPCh. 2.1 - Prob. 2.14PPCh. 2.1 - Prob. 2.15PPCh. 2.1 - Prob. 2.16PPCh. 2.2 - Prob. 2.17PPCh. 2.2 - Practice Problem 2.18 (solution page 149) In...Ch. 2.2 - Prob. 2.19PPCh. 2.2 - Prob. 2.20PPCh. 2.2 - Prob. 2.21PPCh. 2.2 - Prob. 2.22PPCh. 2.2 - Prob. 2.23PPCh. 2.2 - Prob. 2.24PPCh. 2.2 - Prob. 2.25PPCh. 2.2 - Practice Problem 2.26 (solution page 151) You are...Ch. 2.3 - Prob. 2.27PPCh. 2.3 - Prob. 2.28PPCh. 2.3 - Prob. 2.29PPCh. 2.3 - Practice Problem 2.30 (solution page 153) Write a...Ch. 2.3 - Prob. 2.31PPCh. 2.3 - Practice Problem 2.32 (solution page 153) You are...Ch. 2.3 - Prob. 2.33PPCh. 2.3 - Prob. 2.34PPCh. 2.3 - Practice Problem 2.35 (solution page 154) You are...Ch. 2.3 - Prob. 2.36PPCh. 2.3 - Practice Problem 2.37 solution page 155 You are...Ch. 2.3 - Prob. 2.38PPCh. 2.3 - Prob. 2.39PPCh. 2.3 - Practice Problem 2.40 (solution page 156) For each...Ch. 2.3 - Prob. 2.41PPCh. 2.3 - Practice Problem 2.42 (solution page 156) Write a...Ch. 2.3 - Practice Problem 2.43 (solution page 157) In the...Ch. 2.3 - Prob. 2.44PPCh. 2.4 - Prob. 2.45PPCh. 2.4 - Prob. 2.46PPCh. 2.4 - Prob. 2.47PPCh. 2.4 - Prob. 2.48PPCh. 2.4 - Prob. 2.49PPCh. 2.4 - Prob. 2.50PPCh. 2.4 - Prob. 2.51PPCh. 2.4 - Prob. 2.52PPCh. 2.4 - Practice Problem 2.53 (solution page 160) Fill in...Ch. 2.4 - Practice Problem 2.54 (solution page 160) Assume...Ch. 2 - Compile and run the sample code that uses...Ch. 2 - Try running the code for show_bytes for different...Ch. 2 - Prob. 2.57HWCh. 2 - Write a procedure is_little_endian that will...Ch. 2 - Prob. 2.59HWCh. 2 - Prob. 2.60HWCh. 2 - Prob. 2.61HWCh. 2 - Write a function int_shifts_are_arithmetic() that...Ch. 2 - Fill in code for the following C functions....Ch. 2 - Write code to implement the following function: /...Ch. 2 - Write code to implement the following function: /...Ch. 2 - Write code to implement the following function: / ...Ch. 2 - You are given the task of writing a procedure...Ch. 2 - Prob. 2.68HWCh. 2 - Write code for a function with the following...Ch. 2 - Write code for the function with the following...Ch. 2 - You just started working for a company that is...Ch. 2 - You are given the task of writing a function that...Ch. 2 - Write code for a function with the following...Ch. 2 - Write a function with the following prototype: /...Ch. 2 - Prob. 2.75HWCh. 2 - The library function calloc has the following...Ch. 2 - Prob. 2.77HWCh. 2 - Write code for a function with the following...Ch. 2 - Prob. 2.79HWCh. 2 - Write code for a function threefourths that, for...Ch. 2 - Prob. 2.81HWCh. 2 - Prob. 2.82HWCh. 2 - Prob. 2.83HWCh. 2 - Prob. 2.84HWCh. 2 - Prob. 2.85HWCh. 2 - Intel-compatible processors also support an...Ch. 2 - Prob. 2.87HWCh. 2 - Prob. 2.88HWCh. 2 - We are running programs on a machine where values...Ch. 2 - You have been assigned the task of writing a C...Ch. 2 - Prob. 2.91HWCh. 2 - Prob. 2.92HWCh. 2 - following the bit-level floating-point coding...Ch. 2 - Following the bit-level floating-point coding...Ch. 2 - Following the bit-level floating-point coding...Ch. 2 - Following the bit-level floating-point coding...Ch. 2 - Prob. 2.97HW
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