Assembly .byte array

Question

I've defined a byte array using

.data
letters  : .byte 0:26

And i've got some questions : 1 ) Is the first cell in the array available for use, or its employed for other purpose? 2 ) How can I load the 6 ( for example ) cell of the array ?

I've thought about using :

la $t0, letters  # load the array address to $t0
addi $t0, $t0 , 6  # update $t0 in order to get the 6th cell
lb $t1, $t0        # load byte to $t1

Is this method valid or should I do it in other way?

Thanks in advance

What is the processor architecture you are targeting? Please add the appropriate tag next to 'assembly' tag. — nrz, Jan 06 '13 at 13:35
Just FYI, `.byte 0:26` is *not* valid GAS syntax in general for GNU Binutils `as`. It's specific to the assembler in MARS or SPIM, I assume. — Peter Cordes, Nov 15 '19 at 17:36

score 1 · Answer 1 · answered Jan 06 '13 at 12:38

1

1) Yes, it is available 2) Like in C the first cell has zero offset. So this way you will actually point to the seventh cell.

answered Jan 06 '13 at 12:38

Vlad Krasnov

1,027
7
12

Thanks . I'd like to know , the syntex itself is ok ? @Vlad Krasnov – Itamar Jan 06 '13 at 12:39
I don't know this specific assembler language. But on x86 it would look similar. – Vlad Krasnov Jan 06 '13 at 13:07

score 0 · Answer 2 · answered Jan 06 '13 at 14:49

Your code is almost valid, you are just missing a pair of parentheses for indirect addressing, like so:

lb $t1, ($t0) # load byte to $t1

Also, the address can include a constant offset, so in your case you don't have to add that separately:

lb $t1, 6($t0) # load byte to $t1

Note this only works for constants. If you want to index by another register you must do the addition like you did.

Vlad has already answered the other part.

Assembly .byte array

2 Answers2