hw3.txt

CS 61C Su13 Homework 3
Name:Fei Liu
Login:cs61c-ew

Problem 1

a.add, addi, sub

b.Refer to value stored in the destination register

c.andi ,ori

d.57

e.0x10008000   increasing order

f.opcode for xor is 100110 xori is 001110. They are all zero extended.

g.kilobyte is 10 based 10^3 while kibi is 2^10=1024. There is minor rounding
difference.

h.$a3, not preserved

Problem 2

Add comments to each line:

fun:    addi $t0,$zero,32
        # comment here    set $t0 to be 32
        addi $t1,$zero,0
        # comment here    set $t1 to be 0        
loop:    sub $t0,$t0,4
        # comment here    subtract $t0 by 4        
        srlv $t2,$a0,$t0
        # comment here    right logical shift $t0 by value stored in $a0 and
        # store it in $t2       
        andi $t2,$t2,15
        # comment here    $t2 and 15 do logical and save back to $t2       
        slti $t2,$t3,10 
        #comment here     If $t3<10 $t2 is 1 and not $t2 is 0
        bne  $t3,$zero,addLess
        # comment here    if $t3 is not 0 which means that $t2 is $t<10\
        # then go to label addLess 
        addi $t2,$t2,7
        # comment here    add 7 to $t2 variable and store to $t2\
        #This happens when above condition was not satisfied. 
addLess:addi $t2,$t2,48
        # comment here    add 48 to $t2. 
        add  $t4,$a1,$t1
        # comment here    move the pointer right by the amount specified by $t1
        sb   $t2,0($t4)
        # comment here    save the byte to the location specified by $t4
        beq  $t0,$zero,done
        # comment here    if $t0 is 0, then jump to done 
        addi $t1,$t1,1
        # comment here    increment $t1 by 1
        j loop
        # comment here    jump back to label loop
done:   sb   $zero,1($t4)
        # comment here    put a NULL after the last bit pointed by $t4
        jr   $ra
        # comment here    return the function

Explain what is in the array as the function returns (1-2 sentences):

The loop goes over every byte of a 32 bits long binary with 4 bits at a
time and based on the $a0 variable to generate right shifted 4 bit
binaries and convert the range of these binaries from 0-15 to hex(0-E)
format.