CSC263 Computer Org & Arch I - Conditionals/Loops Problem Set

Problem Set: Conditionals and Loops

Given the following code:
```
	.data
prompt:	.asciiz "enter a number: "
	.globl	main
	.text
main:
	li	$t1, 10
	li	$t2, 5
	li	$t3, 2
	li	$v0, 4
	la	$a0, prompt
	syscall
	li	$v0, 5
	syscall
	move	$t0, $v0
	bgtz	$t0, one
	add	$t3, $t1, $t2
one:
	addi	$t2, $t2, -2
	mult	$t0, $t3
	mflo	$t4
```
1. If the user enters 3, what will be the values at the end of execution in the following registers: $t0, $t1, $t2, $t3, and $t4?
2. If the user enters -4, what will be the values at the end of execution in the following registers: $t0, $t1, $t2, $t3, and $t4?

Given the following code:

	.data
prompt:	.asciiz "enter a number: "
	.globl	main

	.text
main:
	li	$t2, 5
	li	$t3, 4
	addi	$t4, $zero, 3
	li	$v0, 4
	la	$a0, prompt
	syscall
	li	$v0, 5
	syscall
	move	$t0, $v0
	li	$v0, 4
	syscall
	li	$v0, 5
	syscall
	move	$t1, $v0
	blt	$t0, $t1, one
	add	$t5, $t1, $t2
	b	two
one:
	add	$t5, $t0, $t2
two:
	mult	$t3, $t5
	mflo	$t6
	div	$t6, $t4
	mfhi	$t2
	mflo	$t3

If the user enters 5 and 2, what will be the values at the end of execution in the following registers: $t0, $t1, $t2, $t3, $t4, $t5, and $t6?
If the user enters 3 and 8, what will be the values at the end of execution in the following registers: $t0, $t1, $t2, $t3, $t4, $t5, and $t6?

What are the values in $t0, $t1, and $t2 at the end of execution of the following code?

	li	$t0, 2
	li	$t1, 15
	addi	$t2, $zero, 0
top:
	bgt	$t0, $t1, end
	add	$t2, $t2, $t0
	addi	$t0, $t0, 2
	b	top
end:

What are the values in $t0, $t1, $t2, $t3, $t4, $t5, $s0, and $s1 at the end of execution of the following code if the user enters: 10 5 15 6 10 20 9 3 18?

	.data
prompt:	.asciiz "enter a number: "
	.globl	main

	.text
main:
	li	$t0, 1
	li	$t1, 3
	li	$t3, 1
	move	$t4, $zero
	li	$v0, 4
one:	bgt	$t0, $t1, six
	move	$t5, $zero
	li	$v0, 4
	la	$a0, prompt
	syscall
	li	$v0, 5
	syscall
	move	$s0, $v0
	addi	$t2, $zero, 0
two:	bgt	$t2, $t3, five
	li	$v0, 4
	la	$a0, prompt
	syscall
	li	$v0, 5
	syscall
	move	$s1, $v0
	blt	$s0, $s1, three
	add	$t5, $t5, $s0
	b	four
three:	add	$t5, $t5, $s1
four:	addi	$t2, $t2, 1
	b	two
five:	add	$t4, $t4, $t5
	addi	$t0, $t0, 1
	b	one
six:

Show the assembler instructions equivalent to each of the following. Be sure to show where each numbered block of code will be placed.

if $t1 != $t2 && $t2 > $t5 {
   .
   . (1)
   .
}
else {
   .
   . (2)
   .
}
.
. (3)
.

if ($t1 <= $t2 || $t3 > $t4) {
   .
   . (1)
   .
}
else {
   .
   . (2)
   .
}
.
. (3)
.

if $t1 > $t2 + $t3 {
   .
   . (1)
   .
}
else if $t3 + $t1 == $t4 {
   .
   . (2)
   .
}
else {
   .
   . (3)
   .
}
.
. (4)
.

   if $t1 <= $t2 {
      .
      . (1)
      .
      if $t3 != 0 {
         .
         . (2)
         .
      }
      else {
         .
         . (3)
         .
      }
   }
   else {
      .
      . (4)
      .
   }
   .
   . (5)
   .

if $t1 >= $t2 {
   if $t0 < $t3 {
      .
      . (1)
      .
   }
   else {
      .
      . (2)
      .
   }
   .
   . (3)
   .
}
else {
   if $t0 != 10 {
      .
      . (4)
      .
   }
}
.
. (5)
.

if $t1 <= $t2 + 1 {
   .
   . (1)
   .
}
else {
   if $t1 > $t2 || $t1 == 0 {
      .
      . (2)
      .
   }
   else {
      .
      . (3)
      .
   }
   .
   . (4)
   .
}
.
. (5)
.

$t1 = 10
while $t1 != 0 {
   $t2 = $t2 + $t3
   $t1 = $t1 - 1
}

$t3 = 0
for ($t1 = 0 ; $t1 < $t2 ; $t1++) {
   print prompt: "Enter a num: "
   read num
   $t2 = num * num
   print $t2
}

$t2 = 0
$t3 = 0
for ($t1 = 0 ; $t1 < 100 ; $t1++) {
   print prompt: "Enter a num: "
   read num
   if num is even
      $t2 = $t2 + num
   else
      t3 = $t3 + num
}
print "Sum of evens: " $t2
print "Sum of odds: " $t3

xton = 1
print prompt: "Enter a num: "
read x
while (x != 0) {
   print "Enter exponent: "
   read n
   for (i = 1 ; i <= n ; i++) {
      xton = xton * x
   }
   print "x^n = "
   print xton
   xton = 1
   print prompt: "Enter a num: "
   read x
}