MCS-284 Chapter 3 Homework (Fall 2001)

When turning in a homework problem, if it is one from the book, you should indicate the exercise number. If it is not from the book, you should indicate the number I give with an x in it, as in 3.x1 below. These will be the reference numbers I use in reporting back your standing on the homework.

Do exercise 3.1 from page 197. Also, write an alternate version of the program that only uses one branch or jump instruction each time through the loop, rather than both a branch and a jump each time. This implies that I still want there to be a loop. As such, please don't use your math knowledge of what the loop is calculating to write a clever version of the procedure that avoids looping at all. Your alternate version should still be as math-dumb as the one in the book (looping doing a bunch of adding, instead of just directly calculating the answer), but should be smarter about the assembly language details of exactly how it loops. You may use additional branch or jump instructions, if you like, that are executed only once regardless of how many times the loop is taken. For an extra challenge, make sure your version should produce the same result as the given one for all integer values of n, rather than only when n is positive.
Do exercise 3.14 from page 200. All instructions involve at least one memory access, namely a read of the instruction itself. Data transfer instructions involve a second memory access, for the data. This data access may be either a read or a write.
Problem 3.x1: Write (in MIPS assembly language) a procedure named whence, such that after calling the procedure with the instruction
```
jal whence
```
the procedure will return (to the next instruction after the jal whence) with the $v0 register containing the address in memory where that jal whence instruction occurs.

Instructor: Max Hailperin