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Assembly Language: multiplying

Posted on 2007-04-11
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Last Modified: 2012-06-21
I am writing a program in MIPS assembly language with PCSpim. I want it to be able to Divide. Here is what I have. Any suggestions?

.data
.globl       firstNum
.globl      secondNum

firstNum:      .asciiz"\nWhat is the First Number?\n"
secondNum:      .asciiz"\nWhat is the Second Number?\n"
space:            .asciiz"\n"
remainder:      .asciiz" Remainder: "
.text
.globl main
main:
addu      $s7, $0, $ra

#Queries user for first number
li      $v0, 4                  
la      $a0, firstNum
syscall
li      $v0, 5                  
syscall
add      $t1,$v0,$zero

#Asks for the second number
li      $v0, 4                  
la      $a0, secondNum
syscall
li      $v0, 5                  
syscall
add      $t2,$v0,$zero

div      $t1,$t2
            
mfhi      $t4
mflo      $t5
      
#Space
li      $v0, 4
la      $a0, space
syscall

add      $a0,$t5,$zero
li      $v0, 1
syscall

#Remainder
li      $v0, 4                  
la      $a0, remainder
syscall

add      $a0,$t4,$zero
li      $v0, 1
syscall

addu      $ra, $0, $s7
jr      $ra
add      $0, $0, $0
0
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Question by:TheTechGuysNYC
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16 Comments
 
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Author Comment

by:TheTechGuysNYC
ID: 18891336
I'm sorry, the title here should be dividing
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Accepted Solution

by:
mr_egyptian earned 250 total points
ID: 18895682
Check here:

http://www.cs.uic.edu/~i366/notes/MIPS%20Quick%20Tutorial.htm

under 'Arithmetic Instructions'

div       $t5,$t6
mflo      $t1
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Expert Comment

by:BrianGEFF719
ID: 18971500
Couple of things:

You really need to check your input of number2 to make sure it's not zero.

Since technically you're doing MOD you want the remainder of the integer division so you dont want the lo-byte , you want the hi-byte. (your code shows this), so use mfhi not mflo.

Now onto my issues with the code:
>> add      $t2,$v0,$zero
Technically this is okay $t2 = $v0 + 0, fine but wouldnt "move $t2,$v0" be easier? You do this several times in your code.

>>add      $a0,$t5,$zero
>>li      $v0, 1
>>syscall

You're outputing a space before this, but this is just the quotient, so you're going to end up with output like for the case of 48 / 7 -> " 6Remainder: 49", is this what you wnat?



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Expert Comment

by:BrianGEFF719
ID: 18971501
Sorry, it should read:

" 6Remainder:1"
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Author Comment

by:TheTechGuysNYC
ID: 18974777
Actually, Brian. I was hoping you would respond... I wanted it to come out "6 Remainder 1" although I guess it really does not matter. As long as the answer comes out correctly...


Why would the move command you suggest be easier?
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Expert Comment

by:BrianGEFF719
ID: 18993038
>>Why would the move command you suggest be easier?

It's not Easier to write...it's Easier to read. That's what you're doing, you're moving something from one place to another if you have an instruction that will do that, then why not use it? Know what I mean?

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Expert Comment

by:BrianGEFF719
ID: 18993042
I have not tested your code but it seems to be correct.
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Expert Comment

by:BrianGEFF719
ID: 18993062
If you would like, tommorrow I will test this code and the code from your multiply question for you.
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Expert Comment

by:BrianGEFF719
ID: 18993070
The code you originally posted works just fine as I thought...It also showed that the division i did in my head was incorrect :0

Output:


What is the first number?
49

What is the second number?
7

6 Remainder: 6
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Author Comment

by:TheTechGuysNYC
ID: 19012740
Yea, unfortunately I tested it further and it does not seem to work with negative numbers for some reason...
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Author Comment

by:TheTechGuysNYC
ID: 19012743
>>It's not Easier to write...it's Easier to read. That's what you're doing, you're moving something from one place to another if you have an instruction that will do that, then why not use it? Know what I mean?


I know exactly what you mean and it makes perfect sense
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Assisted Solution

by:BrianGEFF719
BrianGEFF719 earned 250 total points
ID: 19069364
Try using divi:

divi $t1,$t2
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Expert Comment

by:BrianGEFF719
ID: 19087049
Divi is signed division /w immediate addressing.
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Expert Comment

by:BrianGEFF719
ID: 19248817
I don't think an even split is fair.
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