For my assignment we are given an array of names and an array of integers which represent the ages of the corresponding names (this is basically a dictionary or a map). We are supposed to read in a string from the user, and if that name is in the array, then we print that persons age. Heres what I have so far:
.data
names: .asciiz "steve","john","chelsea","julia","ryan"
ages: .byte 20,25,22,21,23
out1: .asciiz "Please enter a name:"
out2: .asciiz "Age is: "
notfound: .asciiz "Not found!"
input: .asciiz
.text
li $v0, 4
la $a0, out1
syscall #prompts user for name
li $v0, 8
la $a0, input
li $a1, 20
syscall #Reads a name into address "input"
CheckNames: #needs to compare the input string with each element of "names" array and return 1 if they match
la $t0, (names)
la $t1, (input)
beq $t1, $t0, printAge
printAge:
I realize that my CheckNames function is wrong, but I don't know how to iterate through the array of names when each name differs in size (since I can't use an offset to get to the next name)
I faced this problem today. If it still helps you (or anybody else), I overcame this issue using the fact that .asciiz data in Assembly are an especial string of characteres that terminate themselves always with a special signal: NUL. The ASCII's table below could help ilustrate this:
ASCII Table
Keeping in mind that every character fills 8 bits (1 byte) of information, you can use these knowledge to go through all the bytes in the string's array and identify the end of each world by comparing the load byte with the $0 register (or a register with data equivalent with zero).
A pseudo-code is presented below to help you construct your own code:
move $a1, $s0 # $s0 register store the normal index of the string names(1), for example
li $t0, 0
li $t2, 0 # cont to know how many word did you pass
li $t1, maxSpace # maxSpace is that maximum space in the array
while ($t2<$t1) {
branch to "final", if $t1 == $a1
lb $t3, names($t0)
branch to "isnotNUL", if $t3 != $0
$t2 = $t2 + 1
$t0 = $t0 + 1
isnotNUL:
$t0 = $t0 + 1
}
# normal part of code to print a string .asciiz passing the start adress to $a0
final:
li $v0, 4
la $a0, names($t0)
syscall
jr $ra
There is just one problem with this method: the iteration could be very slow - specially if the array is big and the strings are also big. If this is your case and you don't want that, you could modify the code to save the numbers of bytes each string of the array has and construct a LUT (Look up table) with this information. So, you would run this function on the start of the program and when the time to print the information has come, you already know the adress you shuold start by loading the initial adress of the array and adding to it the number saved on the LUT.
Related
I am trying to create an integer array in MIPS wherein the user can choose the size and numbers that will be stored. For some reason, my program does not branch to the end loop when the array is full.
I apologize if the solution is glaringly obvious. This is homework, so I am not looking to plagiarize full code answers, but rather if I could be pointed towards the right direction I would appreciate it greatly. Thanks for looking.
.text
.globl __start # for PCSPIM //main for qtspim instead of __start
__start:
la $a0,pr1 # Ask user for amount of integers desired to be entered
li $v0,4 # a0 = address of string
syscall # v0 = 4, indicates display a string
li $v0,5 # Command to read an integer
syscall
sw $v0,count # Store int read into count
lw $t0,array # Point t0 to array
lw $t1,count # Point t1 to count
M_LOOP:
la $a0,pr2 # Prompt for integer
li $v0,4 # a0 = address of string
syscall # v0 = 4
li $v0,5 # Command to read an integer
syscall
beqz $v0, E_LOOP
sw $v0, array($t0) # Move the integer into the array
addi $t0,$t0,4 # Increment count by 4
sub $t1,$t1,1 # Subtract 1 from $t1
bnez $t0,M_LOOP
E_LOOP:
li $v0,10 # End Of Program
syscall # Call to system
.data
array: .space 100
pr1: .asciiz "Amount of integers to be entered: "
pr2: .asciiz "Integer to be inserted into array: "
newl: .asciiz "\n"
count: .word 0
First of all, I have already checked related questions to this one, yet I am still not able to overcome the problem I have with this program.
What I am trying to do is, basically, take a byte[] input and duplicate it to another byte[], and print the duplicate array. My code is as above:
.data
hello: .asciiz "hello"
inp: .byte 5
dup: .byte 5
.text
main:
la $a0, inp #get input
li $v0, 8
syscall
la $s0, dup #load arrays on s0 and s1
la $s1, inp
li $t0, 0 #instantiate offsets as 0
li $t2, 0
Load:
lb $t1, 0($s1) #load first byte
sub $t1, $t1, 48 #test if it is <0
bltz, $t1, exit #if so go to exit
add $t1, $t1, 48
sb $t1, 0($s0) #else save the byte
add $s1, $s1, 1 #increment offsets
add $s0, $s0, 1
j Load
la $a0, hello
li $v0, 4
syscall
exit:
li $t1, 0
add $s0, $s0, 1
sb $t1, 0($s0) #add null to the end of dup
la $a0, dup
li $v0, 4
syscall
jr $ra
I am new to MIPS and, I am not able to recognize what the problem is.
By the way, I am passing 123 as an input and I am getting countless of 1s as output, which tells me that I am stuck in the loop and never getting any further in $s1 (inp).
There are a couple of problems with your code:
First, .byte 5 doesn't reserve space for 5 bytes, it declares a single byte with the value 5. If you want 5 bytes you should say .space 5 (the bytes will be initialized with the value 0 IIRC).
Second, syscall 8 takes one more argument; $a1 = maximum number of characters to read, which you haven't specified. If you have room for 5 bytes in your buffer you should set $a1 to 5. Note that "maximum number of characters to read" actually means "maximum number of characters to read including the terminating null-character".
.data
array: .word 0:5
prompt1: .asciiz "enter number: "
newline: .asciiz "\n"
.text
add $t2,$zero,$zero # initializes counter to 0
la $s0, array # stores the beginning of array into $s0
secretcode:
li $v0, 4 # prints "enter number: "
la $a0, prompt1
syscall
li $v0, 5 # reads in user input
syscall
sw $v0, ($s0) # saves user input into address at $s0
addi $s0, $s0, 4 # increments address at $s0 by 4 bytes
addi $t2, $t2, 1 # increments counter by 1
bne $t2, 5, secretcode # stops loop when loop executes 5 times
printsecretcode:
lw $a0, ($s0) # print first element
li $v0, 1
syscall
li $v0, 10 # system code halt
syscall
The program is supposed to store 5 user inputted numbers into an array. I tried to print the first value but it comes up as a large number which I assume is an address. How would I print the actual value of the number so that I know it saved correctly?
By the time you reach your printing code $s0 contains the address array + 4*5, so what you end up printing is the 32-bit number formed by the first four characters of the "enter number: " string.
To fix this, add an la $s0, array before you try to print the first element.
Overview of program: Input of a number 1-26, give the corresponding Capital letter too the number
My logic: Set up an Array type "structure" using .byte with chars. have a counter going through the array. once the counter is equivenlt to the input number print out the current point at the array.
This is a homework assignment so I'm not trying to "nudge" out the answer but guidance would be very helpful.
This is why where I think its going wrong. When I add 1 to the address it for some reason gives me a error. But when i add 4 it works fine? A char is supposed to take only 1 bit correct? I understand that when indexing address's of ints in an array it should be by 4.
.data
prompt: .asciiz "Enter the value of n here: "
larray: .byte 'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'
.globl main
.text
main:
la $t1, larray # Loads Array addresss into $t1
li $v0, 4 # System call for Print String
la $a0, prompt # Load address of prompt into $a0
syscall # Print the prompt message
li $v0, 5 # System call code for Read Integer
syscall # Read N into $v0
move $t3, $v0
li $t0, 0 # Loads int 0 into $t0
loop:
beq $t0, $t3, end # Break
lw $a0, ($t1) # Loads current pointer
addi $t0, $t0, 1 # Adds one to $t0 (Counting up +1)
addi $t1, $t1, 1 # Advances to next address in the array
j loop
end:
li $v0, 11 # Print at current index
syscall
li $v0, 10 # return control to system
syscall
I did do research on how to access the char a different way, but I don't think I can implement this way because you would need it hard coded?
Link:
This is the Stack Link that I found
There's no need for the array or the loop. If all you want to do is find the corresponding capital letter for a single number in the range 1-26, this would suffice:
li $v0, 5 # System call code for Read Integer
syscall # Read N into $v0
addiu $v0,$v0,'A'-1 # Convert the number 1-26 to the character 'A'-'Z'
A char is supposed to take only 1 bit correct?
One byte.
When I add 1 to the address it for some reason gives me a error. But when i add 4 it works fine?
You're using the lw instruction, which loads one word (4 bytes). To load a single byte, use the lb or lbu instruction (lb is for signed bytes, lbu for unsigned).
I have this homework problem .
Write a program that produces the following sequence; 1,2,2,4,8, 32, 256,… and stores it in an array, depending on the number of terms chosen by the user. Each element in the sequence can be calculated by multiplying the two elements preceding it. In other words the nth sequence number Sn is calculated by the equation Sn=Sn-1×Sn-2.
I tried but it didn't run
My code
^
^
# UNTITLED PROGRAM
.data # Data declaration section
str1: .ascii "Please enter the number of terms to produce: "
arr: .space 40
.text
main: # Start of code section
li $v0, 4 # system call code for printing string = 4
la $a0, str1 # load address of string to be printed into $a0
syscall # call operating system to perform print operation
li $v0, 5 # get ready to read in integers
syscall # system waits for input
move $s0,$v0 # store the result of the read (returned in $v0) in num1
la $s1,arr
addi $t2,$zero,2 # i=2
addi $t0,$zero,1
add $t1,$t0,$t0
sw $t0,0($s1)
sw $t1,0($s1)
L1:
addi $t2,$t2,1 #i++
addi $s1,$s1,4
lw $t4,0($s1) #A[i-1]
lw $t5,4($s1)
mul $t3,$t4,$t5
sw $t3,8($s1)
beq $t2,$s0,print
j L1
print:
lw $t3,0($s1)
li $v0, 1 # system call code for print_int
move $a0, $t3 # integer to print
syscall # print it
addi $s1,$s1,4
beq $t2,$s0,Exit
j print
Exit:
li $v0, 10 # exits program
syscall
# END OF PROGRAM
MARS error message:
Error in line 26: Runtime exception at 0x00400030:
store address not aligned on word boundary 0x1001002d
The error message is telling you that you're trying to access memory with an illegal (non word-aligned) address at this instruction:
sw $t0,0($s1)
When you have problems like this, you need to use the debugger. First, set a break point at the instruction where the exception is thrown.
Run the program, and when it stops at the break point, check the address (in $s1) you're trying to access. You'll see that it's 268501037 or 0x1001002d, and since it ends with a 7, it's not word-aligned.
$s1 has the correct array address, but I think you're assuming that when you created the array in the data segment, that it would start at a word-aligned address. This is not the case. To resolve this, you need to align the data.
.data # Data declaration section
str1: .ascii "Please enter the number of terms to produce: "
.align 2
arr: .space 40