How to count the total of numbers from input in LMC

Question

I'm struggling a bit on this question. Essentially, I have to loop through a code with inputs, until the input is 0. Doing that by BRZ. And then, I have to output how many numbers that have been typed in to input. If I have typed in 1, 4, 6, 2, then the input should be 4, since there's four numbers there.

This is the code I'm currently using

start   INP antall
        BRZ jump
        ADD tall
        STA tall
        BRA start
jump    LDA tall
        OUT
antall  STA
        LDA
        OUT
        HLT
tall    DAT 0
antall  DAT

antall = total tall = numbers if anyone's wondering what the labels mean

Answer 1

Some comments on your code:

• INP does not take an operand: it should be used on its own, not like INP antall. The user's input is loaded into the accumulator, so it doesn't need any parameter.

• Labels should be unique. You have defined two lines with the label antall, once for the STA (which can be removed) and once as the location for the end result.

• ADD tall adds the value in tall to the accumulator. But at that moment the accumulator holds the last input value, which is not something you want to include in the addition. Instead, you want to load the current value of tall, and then add 1 to it. So you need a mailbox with the value 1 in it. You could define it near the end of your code block:

  one  DAT 1
  

• You have both tall and antall locations, but as both uses you have for antall should be removed, that label and mailbox no longer have a purpose. You can just keep tall.

• You have a STA and a LDA without mention where to store/retrieve the value. Moreover it seems unnecessary code for doing what you ask about.

• There are two OUT instructions in your code, but reading the question you only need to output one thing: the number of inputs.

Here is the corrected code -- you can run it here:

#input: 1 4 6 2 0
start   INP
        BRZ jump
        LDA tall
        ADD one
        STA tall
        BRA start
jump    LDA tall
        OUT
        HLT
one     DAT 1
tall    DAT 0


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