CODEWITHSUNDEEP
assemblymipsemulation
Brianna Drew
Brianna Drew

Reputation: 109

Beginner to MIPS, why won't it print my third prompt?

I'm trying to write a program in MARS (MIPS Assembler and Runtime Simulator) that will take two integers from the user and then either add or multiply based on what the user chooses to do. Anyways, I haven't gotten too far into the program yet, however I really can't figure out why it won't print my 3rd prompt out. Can you please help me?

.data
prompt1: .asciiz "Enter an Integer!"
prompt2: .asciiz "Enter Another Integer!"
prompt3: .asciiz  "Would you like to add or multiply? (+ for add, * for multiply)"
resultout: .asciiz "The result is:"

.text

main:
    la $a0, prompt1
    li $v0, 4
    syscall
    li $v0, 5
    syscall
    add $t0, $v0, $zero

    la $a0, prompt2
    li $v0, 4
    syscall
    li $v0, 5
    syscall
    add $t1, $v0, $zero

    la $a0, prompt3
    li $v0, 12
    syscall
    li $v0, 11
    syscall
    add $t2, $v0, $zero

Upvotes: 1

Views: 293

Answers (1)

user1531971
user1531971

Reputation:

To print the prompt and fetch the single character I think you need to load immediate to $v0 the correct value for the syscall. According to the MARS 4.5 Help file, the Table of Available Services suggest that your code should be something like this from line 24 on:

la $a0, prompt3
li $v0, 4
syscall
li $v0, 12
syscall

That is, you want to "print string" whatever is in prompt3 and then "read character" to get the single character. The first syscall you make is 12, which is "read character" so it was waiting for you to input something.

I recommend putting magic numbers like 4 and 12, which represent specific system calls, into the code as constants:

.eqv SYS_PRINT_STRING 4
[...]
li $v0, SYS_PRINT_STRING

Upvotes: 1

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