I have an unknown output error after entering 2nd value which is after entering base number.
Hopefully,some of you could identify my error:
ERROR:Instruction references undefined symbol at 0x00400060
[0x00400060] 0x102a0000 beq $1, $10, 0 [hex-0x0040005c]
PROGRESS:Currently stucked at Step 2.
What i want to do is,
1)User enter a decimal value
2)User enter type of conversion
3)Go to desired subroutine depending on type of conversion chosen earlier
4)Display output
.data
prompt: .asciiz "Enter the decimal number to convert: "
base: .asciiz "Select type of base (2 for binary,16 for hexadecimal or 8 for octal): "
ans1: .asciiz "\nBinary Output is equivalent:"
ans2: .asciiz "\nOctal Output is equivalent:"
ans3: .asciiz "\nHexadecimal Output equivalent:0x"
result1: .space 8
.text
.globl main
main:
la $a0, prompt #Display message
li $v0, 4
syscall
li $v0, 5
syscall
beq $v0, $zero, Exit #Exit if 0 decimal is entered
move $t0, $v0 #Else copy value entered into temporaries
askbase:
li $v0, 4
la $a0, base #Display message
syscall
li $v0, 5
syscall
add $t1,$zero,$v0 #Add desired value/base entered into t1
beq $t2,16,hex #if base 16 is entered,goto hex subroutine
beq $t2,8,oct
beq $t2,2,bin
la $a0, ans3
li $v0, 4
syscall
li $t0, 8 # counter
la $t3, result1 # where answer will be stored
Hex:
beqz $t0, Exit # branch to exit if counter is equal to zero
rol $t2, $t2, 4 # rotate 4 bits to the left
and $t4, $t2, 0xf # mask with 1111
ble $t4, 9, Sum # if less than or equal to nine, branch to sum
addi $t4, $t4, 55 # if greater than nine, add 55
b End
Sum:
addi $t4, $t4, 48 # add 48 to result
End:
sb $t4, 0($t3) # store hex digit into result
addi $t3, $t3, 1 # increment address counter
addi $t0, $t0, -1 # decrement loop counter
j Loop
Exit: la $a0, result1
li $v0, 4
syscall
la $v0, 10
syscall
It looks like you have a typo at line 29 beq $t2,16,hex should be beq $t2,16,Hex. Note the capital letter on Hex. You also have a number of undefined labels: Loop, oct, bin... Without those labels you are going to have issues. It is a good idea to just set some up as place holders (until you have their subroutines defined). Maybe have them all branch to Exit:. The assembler cannot resolve your branch instructions without having the actual labels to go to.
You haven't stored anything in $t7, so there's no particular reason to expect that $t7 would equal 16.
What you probably wanted to write is:
beq $t1,16,hex
Since $t1 is the register that you stored the base in.
However, I really don't see why you would want that jump with the way the code currently is structured. The hex subroutine relies on a few registers (like $t0 and $t3) to have been initialized to certain values, and that initialization would be skipped if that beq is taken.
Related
goodday, so currently my code prompts the user to enter a sum. my program then takes these stored values and outputs the sum of them. However, currently my code is not outputting the correct total and i am unsure where the problem lies.
i have attached my code below:
.text
main:
#Prompt
la $a0, prompt
li $v0, 4
syscall
# Get input string
li $v0, 8
la $a0, string_input
li $a1, 1024
move $t0, $a0
syscall
# initialise sum
lb $t2, ($t0) # Initialise the sum as the first value
addi $t2, $t2, -48 # Convert to decimal value
addu $t0, $t0, 1
b loop
loop:
lb $t3, ($t0) # Store the sign
lb $t1, 1($t0) # Store the value
addu $t0, $t0, 2 # increment the counter
beq $t1, 10, end_loop # If reached the end of the string
# Manipulate sign value to 1 if '+'
add $t3, $t3, 4
add $t2, $t2, $t1 # Add the value to the sum
b loop # re-iterate
end_loop:
# Printing the total sum
move $a0, $t2
li $v0, 1
syscall
# Exiting program
li $v0, 10
syscall
.data
string_input: .space 1024
prompt: .asciiz "Enter a sum:\n"
the current output should be 11 but this is what is outputted instead:
Enter a sum:
2+3+6
727
So I am fairly new to mips and am trying to do a hmwk.
The exercise is to create a block of words with 0 as the last word , to count them knowing we don't consider the last element 0 and print out the result.
Here is my code for the moment
.data
blockOfWords: .word 12,43,549,7,60,0
.text
la $a0, blockOfWords #putting address of blockOfWords in $a0
loopStart: sll $t1, $s3,2 #iterates thru blockOfWords by jumping by 4 bytes, $t1=4*i
add $t1,$t1,$a0 #we increment the address by four so as to advance in the array after every iteration
lw $a1, 0($t1) #$a1=blockOfWOrds[i]
beq $a1,$zero, Exit #if the value in $a1[i]==0, exit the loop
addi $s0,$s0,1 #else, increment by one the cnt=$s0
j loopStart #and continue looping thru blockOfWords
Exit:
#how do i print the result?
So instead of doing a shift left logical it is a lot easier to up the memory address in the array
In this way the lw $a1, 0($a0) is just grabbing the beginning of the word
it is then incremented by 4 after a check for the 0. This makes the function much simpler and easier to read.
.data
blockOfWords: .word 12,43,549,7,60,0
.text
main:
la $a0, blockOfWords # Load beginning address into $a0
loopStart:
lw $a1, 0($a0) # load the value at the beginning of $a0 into $a1
beq $a1,$zero, exit # Check if $a1 is 0, if so jump to exit
addi $s0,$s0,1 # Add one to the count
addi $a0, $a0, 4 # Up the intial index of the array by 4, up one word
j loopStart # Re-loop
exit:
li $v0, 1 # Load the value of 1 into the $v0 register
la $a0, ($s0) # Load the counter into the $a0 address
syscall
li $v0, 10 # A value 10 syscall to indicate end of program
syscall
I am trying to print on the console the values of the array, which are already given as intA in .data. I.e., trying to print values of an array without user's prompt.
My code:
.data
prompt: .asciiz "The values in the array are:\n"
finished: .asciiz "\nNo more values to present"
space: .asciiz " "
intA: .word 11, 2, 3, 4, 5, 34, 0
.text
.globl main
main:
#Prints the prompt string
li $v0, 4
la $a0, prompt
syscall
# initialization of a0, a1, and t3 (i, counter)
la $a0, intA # loading starting address (base) of array in register a0
addi $a1, $zero, 6 # array size - 1
addi $t3, $zero, 0 # i initialized to 0
j loop
loop:
lw $t1, 0($a0) # loading integer (value of array) in the current address to register t1, I use lw because integer is a word (4 bytes)
# printing current value of array
li $v0, 4
la $a2, ($t1)
syscall
# spacing between values
li $v0, 4
la $a2, space
syscall
# checking that next address is not outside of the array
addi $t3, $t3, 1
slti $t2, $t3, 6
bne $t2, 1, done
# accessing next integer and jumping back to print it
addi $a0, $a0, 4
j loop
done:
# indicating program is done
li $v0, 4
la $a0, finished
syscall
The output that I am getting: output
Any idea why it doesn't print the values of the array, and also what are these squares that are printed instead?
Edit:
I changed
# printing current value of array
li $v0, 4
la $a2, ($t1)
syscall
to
# printing current value of array
li $v0, 1
lw $a2, ($t1)
syscall
Because, from what I understand, I print an integer so $v0 should be fed 1, and I should lw and not la (because it is an integer, i.e, a word)
However, now I get a runtime error in line 31: lw $a2, ($t1) Telling me that
fetch address not aligned on word boundary 0x0000000b
Solution: Instead of lw $a0, ($t1) for printing the value of $t1, I need to do add $a0, $t1, $zero, because I am trying to use the value and not to access an address.
If given a number, I want to print out the first 'x' number of letters from the alphabet. I've setup a counter to determine the number of iterations the loop goes through, but I do not know how to extract the correct number of letters from the alphabet string.
Here's what I've done so far:
.data
alphabet:
.space 28
msg1: .ascii " Please enter an integer from 1-26:"
msg2: .ascii "abcdefghijklmnopqrstuvwxyz"
.text
.globl main
main:
li $v0, 5 # syscall for read_int
syscall
add $a0, $v0, $zero
li $t0, 0
li $t1, 26 # loop will start from zero and iterate to 26
loop:
la $t2, 0($a0)
beq $t0, $t2, end # once $t1 and $a0 are equal, loops stops
#li $t2, 1
#blt $t1, $t2, nomodify # do nothing if int less than 0
#li $t2, 26
#bgt $t0, $t2, nomodify # do nothing if int greater than 25
addi $t0, $t0, 1 # add 1 to $t1
j loop # jump back to top
end:
# Here is where I want to take 'x' number of iterations and convert it to
# the string of 'x' letters
li $v0, 10
syscall
Any help would be appreciated.
Having all the characters in a string is unnecessary for this task. Characters are integers, so you can just start at 'a' and count upwards:
# Assuming the loop count is in $t0
li $a0, 'a' # start at character 'a'
print_chars:
li $v0, 11
syscall # syscall 11 = print_character
addiu $a0, $a0, 1 # set $a0 to the next character
addiu $t0, $t0, -1
bne $t0, $zero, print_chars
I'm trying to write a program in MIPS that continuously prompts for two integers and prints the sum until the sum is 0. The trick is that if the sum is 13, I need to call a method to change the assembled MIPS code so that
add $t2, $t0, $t1
becomes
and $t2, $t0, $t1
and all subsequent runs of the loop use the and instruction.
I have the summation loop working so that when 13 is the sum the method instMod is called which I want to modify the instruction. Unfortunately, I have no idea where to start and can't find any examples of this online. I assume I need to somehow get the hex code of the add out of the assembled code and replace it with the hex code for the and but I do not know how to do that or if that is the right course of action to take.
# Nick Gilbert
# MIPS Program to demonstrate self-modifying code
.data
num1Prompt: .asciiz "Enter num1: "
num2Prompt: .asciiz "Enter num2: "
num1: .word 0
num2: .word 0
addOut: .asciiz "ADD: "
andOut: .asciiz "AND: "
.text
main:
sumLoop:
la $a0, num1Prompt #Asking user for num1
li $v0, 4 #Call code to print string
syscall
li $v0, 5 #Call code to read an int
syscall
move $t0, $v0 #Moving read int to $t1
la $a0, num2Prompt #Asking user for num2
li $v0, 4 #Call code to print string
syscall
li $v0, 5 #Call code to read an int
syscall
move $t1, $v0 #Moving read int to $t2
add $t2, $t0, $t1 #Adding num1 and num2 together
la $a0, addOut
li $v0, 4
syscall
move $a0, $t2
li $v0, 1
syscall
beq $t2, 13, instMod #Calling method to modify add instruction if sum = 13
bne $t2, 0, sumLoop #If result is not yet 0, ask for new sum
endSumLoop:
li $v0, 10
syscall
instMod: #Method to change add instruction to an and instruction
Add a label at the instruction you want to replace, e.g:
instruction_to_be_replaced:
add $t2, $t0, $t1 #Adding num1 and num2 together
then in your routine instMod
instMod: #Method to change add instruction to an and instruction
lw $t1, instruction_to_replace
sw $t1, instruction_to_be_replaced
j sumLoop # go back to your sumLooop
instruction_to_replace:
and $t2, $t0, $t1
The code loads in temporary register $t1 the contents of the instruction you want to replace, and then stores it in the location labelled instruction_to_be_replaced.
The "source" of the instruction goes labelled in instruction_to_replace.
To do this, you need to be able to write on the code section which I assume you have otherwise you would not be asking this question.
Try this:
Assemble the instruction that you need to an object file
Extract the hexadecimal of the equivalent machine code
Place a label in front of the code you need to change
mov the hexidecimal from step 2 into the location from step 3 in your instMod section
For this to function the two instructions with operands must be of identical length. If they are not, pad the original or the replacement with nop as appropriate.