Description
1. [20] 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 the case that mask is called with input 32 (hint: shifting a 32-
bit word by 32 in either direction is undefined in standard C, so don’t do it; another hint: the int
return type can be exploited to handle this case).
Here are some test runs:
mask(1): 0x1
mask(2): 0x3
mask(3): 0x7
mask(5): 0x1F
mask(8): 0xFF
mask(16): 0xFFFF
mask(32): 0xFFFFFFFF
Use only bitwise operators and subtraction; no if statements, loops, or other arithmetic
operators (+, *, /, %). Also write a main() function to test your function. Name your source file
2-1.c
2. [20] 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. Name your source file
2-2.c
3. [15] 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 ux = *((unsigned *) &x); // convert x raw bits
unsigned uy = *((unsigned *) &y); // convert y raw bits
unsigned sx = ux >> 31; // extract sign bit of ux
unsigned 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 operators; no if statements, loops, or arithmetic operators (+, -, *, /, %). Also
write a main() function to test your function. Name your source file 2-3.c
4. [15] Convert the following hex values to decimal assuming that they are stored as 2s
complement integers.
a. (5) 0x000000FF
b. (5) 0xFFFFFCE6
c. (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:
a. (5) 0x80000000
b. (5) 0x41220000
c. (5) 0xC39D0000
Write your answers in your solutions document. Show your work.
6. [15] 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
b. (5) 8.25
c. (5) -25.125
Write your answers in your solutions document. Show your work.
Zip the source files and solution document (if applicable), name the .zip file Assignment2.zip (e.g., EricWillsAssignment2.zip), and upload the .zip file to Canvas (see
Assignments section for submission link).
