CS301 – Fall 2001

Prof. Hartman

Homework #4

Due Monday, October 8^th by 5:00 pm

• Chapter 7 problem 4.
• Chapter 7 problem 8.
• Chapter 7 problem 10.

• Write an assembly language program that counts the number of “1” bits in a doubleword in two different ways. First, use a rotate or shift command (inside a loop). Second, encode the method shown below in C into assembly language.

int bit_count(unsigned int x )

{

int cnt = 0;

while( x != 0) {

x = x & (x-1);

cnt++;

}

return cnt;

}

Write your code using subroutines, and use no static variables – that is, your .data and .bss segments should be empty except for string data. (If you need local variables, use stack space as in local1.asm or local2.asm) Pass any parameters to your routines on the stack, and return the answer in EAX. Your program should ask the user to enter an integer, and report the answer that each subroutine returns.

You may use the I/O routines from Carter’s book. Refer to the handout about using NASM with Windows and Visual C++ for links to the I/O files if you don’t have them. For full credit you must turn in a well-commented listing including your name and the problem number.