I am using something like SPIMS or MARS with syscall functions.
I am reading in a string (and it works because I can print it out) as follows:
li $v0, 8
la $a0, string
li $a1, 256
syscall
However, I am having a problem accessing a single character of the string. So if I want to access the first character and print it, I am trying this:
la $t0, string
lb $a0, ($t0)
li $v0, 4
sys call
If I try something like this:
la $a0, string
li $v0, 4
syscall
This prints out the whole string as string points to the whole string.
If I try something like:
la $a0, string
lb $a0, ($t0)
li $v0, 4
syscall
It gives me an out of bound error. I don't understand why though - isn't a character a byte long and this just loads the first byte from the string into $a0?
Thank you
Looking at the documentation for the MARS syscall functions you can see that service 4, which you're using, expects $a0
to be "[the] address of null-terminated string to print", which explains the behavior you're seeing.
What you want is function 11 "print character", which prints the low-order byte as a character. In other words the following should work (not tested):
la $t0, string
lb $a0, ($t0)
li $v0, 11
syscall