[SOLVED] CS314 Lab 2

Description

1. Suppose we number the bits in a 32-bit word from 0 (least significant) to 31 (most significant). Write code for the following C function that will return a bit mask containing 1s for the least-significant n bits and 0s for the remaining most-significant bits:

int mask(int n);

Your solution will need to handle values of n on the range [0, 31] (i.e., 0 up to, and including, 31).

Here are some test runs:

mask(0): 0x0 mask(1): 0x1 mask(2): 0x3 mask(3): 0x7 mask(5): 0x1F mask(8): 0xFF mask(16): 0xFFFF mask(31): 0x7FFFFFFF

Use only bitwise operators and subtraction; no if statements, loops, or other arithmetic operators (+, *, /, %).  Also write a main() function to test your function.

Hint: you can use subtraction on this one – please do.

Name your source file 2-1.c

2.  Suppose we number the bytes in a 32-bit word from 0 (least significant) to 3 (most significant) and that the word consists of 4 individual signed bytes. Write code for the following C function that will return byte i of x sign extended to 32 bits: unsigned int extract (unsigned int x, int i);

Here are some test runs:

extract(0x12345678, 0): 0x00000078 extract(0xABCDEF00, 2): 0xFFFFFFCD

Use only bitwise operators and subtraction; no if statements, loops, or other arithmetic operators (+, *, /, %).  Also write a main() function to test your function.

Hint: arithmetic shift is your friend with regard to sign extension.

Name your source file 2-2.c

3. Fill in the missing expression in the following C code such that it will return 1 if x is >= y, 0 otherwise (you can assume that neither argument is NaN and that +0 and -0 are considered equal):

int ge(float x, float y) {

unsigned int ux = *((unsigned int*) &x); // convert x raw bits     unsigned int uy = *((unsigned int*) &y); // convert y raw bits     unsigned int sx = ux >> 31; // extract sign bit of ux     unsigned int sy = uy >> 31; // extract sign bit of uy         ux <<= 1; // drop sign bit of ux     uy <<= 1; // drop sign bit of uy     // TODO: return using sx, sy, ux, uy

}

Here are some test runs:

ge(0.0f, 0.0f): 1 ge(-0.0f, 0.0f): 1 ge(-1.0f, 0.0f): 0 ge(0.0f, 1.0f): 0 ge(1.0f, 0.0f): 1 ge(0.0f, -1.0f): 1

Use only bitwise, logical, and relational (==, !=, <, <=, >, >=) operators; no if statements, loops, or arithmetic operators (+, -, *, /, %).  Also write a main() function to test your function.

Hint: you’re going to want to “or” together all of the cases in which the function will return 1.  For example, (ux == 0 && uy == 0) will be true only if x is either +0.0f or -0.0f and y is either +0.0f or -0.0f.

Name your source file 2-3.c

4. Convert the following hex values to decimal assuming that they are stored as 32-bit 2s complement integers.
5. (5) 0x000000C6
6. (5) 0xFFFFFEC6
7. (5) 0xFFFFFFFF

Write your answers in your solutions document.  Show your work.

5. [15] Convert the following hex values to decimal assuming that they are encoded as IEEE 754 single-precision floating-point numbers:
6. (5) 0x80000000
7. (5) 0x439D0000
8. (5) 0xC1340000

Write your answers in your solutions document.  Show your work.

6. Convert the following decimal numbers to hex encoded as IEEE 754 single-precision floating-point numbers. Write your answers in your solutions document. a. (5) -1.0
7. (5) 16.75
8. (5) -314.0