Assembly MIPS - How do I store an integer from the user into memory?

Eric Diviney picture Eric Diviney · Mar 4, 2015 · Viewed 21.6k times · Source

So, I have no idea how assembly works or what I'm doing. I thought I did, but of course I was wrong. So here's my question - I don't even know how to let a user enter an integer so I can store it in memory. I also don't know if my variables are aligned because I don't even understand what "alignment" really is. Below is my assembly code, along with comments demonstrating what I'd LIKE for the code to be doing. Please help

.data
                    # variables here

intPrompt:                  .asciiz "\nPlease enter an integer.\n"
stringPrompt:               .asciiz "\nPlease enter a string that is less than 36 (35 or less) characters long.\n"
charPrompt:                 .asciiz "\nPlease enter a single character.\n"
int:                    .space 4
string:                     .space 36
char:                   .byte  1







                    .text
                    .globl main
main:

                    # print the first prompt
                    li $v0, 4
                    la $a0, intPrompt
                    syscall


                    # allow user to enter an integer
                    li $v0, 5
                    syscall

                    # store the input in `int`
                    # don't really know what to do right here, I want to save the user inputed integer into 'int' variable
                    sw $v0, int
                    syscall

Answer

Danil Parshukov picture Danil Parshukov · Nov 18, 2016

You should change type of "int" variable from .space to .word

finally it should look like this:

.data
                    # variables here

    intPrompt:                .asciiz "\nPlease enter an integer.\n"
    stringPrompt:             .asciiz "\nPlease enter a string that is less than 36 (35 or less) characters long.\n"
    charPrompt:               .asciiz "\nPlease enter a single character.\n"
    int:                      .word
    string:                   .space 36
    char:                     .byte  1

main:

    li $v0, 4         #you say to program, that you're going to output string which will be in the $a0 register
    la $a0, intPrompt #here you load your string from intPromt var. to $a0
    syscall           #this command just executes everything that you have written before >> it prints string, which is in $a0

    li $v0, 5         #this command says: "Hey, read an integer from console and put it in $v0!"
    syscall           #this command executes all previous commands ( li $v0, 5 )

    sw $v0, int       #sw -> store word, here you move value from $v0 to "int" variable
    syscall           #executes (sw $v0, int), here you have your input number in "int" variable

You can find more detailed information here