Design an algorithm to input 2 numbers and then output the lowest number in little man computing

Question

I have a program I'm doing and I want to input two numbers so that the LMC can output the smallest one. MY code is giving me the biggest number, help me fix it.

INP
STA first
INP
STA second

SUB second
BRP secondBig
LDA second
OUT
BRA endProgram
secondBig LDA second
OUT
endProgram HLT
first DAT
second DAT

Fixing simple problems like this yourself is a much better way of *learning* than just copying someone else's solution. If your goal is to learn. — rici, Oct 20 '17 at 18:58
As Scott Hunter already pointed out, you're printing the second value in both branches. Also note that you're testing **second - second**, which will not give you any useful information. Please give us the pseudo-code you are trying to implement. — Prune, Oct 20 '17 at 20:27

score 0 · Answer 1 · answered Oct 20 '17 at 18:49

0

Invert your conditional branch: use BRN (branch negative) instead of BRP. Alternately, switch the logic branches that decide which value will be available for output.

answered Oct 20 '17 at 18:49

Prune

76,765
14
60
81

Okay let me try that – Jeff Oct 20 '17 at 18:58
program halted at BRN, is it possible to rewrite the code for me – Jeff Oct 20 '17 at 19:02
1

`BRN` isn't a valid instruction. – Scott Hunter Oct 20 '17 at 19:16
you said branch negative – Jeff Oct 20 '17 at 19:17
My mistake -- wrong instruction set. I'll correct the answer when you clarify the problem (see comment on the posting). – Prune Oct 20 '17 at 20:24

Scott Hunter · Accepted Answer · 2017-10-20T19:18:44.980

0

You're storing both input values in first, which means you overwrite the first one with the second.

Both before and after fixing the above, your code isn't outputting the biggest, it is outputting the second (regardless of relative size). Single-stepping, or actually reading the code, should tell you why.

edited Oct 20 '17 at 19:18

answered Oct 20 '17 at 18:51

Scott Hunter

48,888
12
60
101

sorry, it was a mistake please check the code again – Jeff Oct 20 '17 at 18:59

score 0 · Answer 3 · answered Sep 25 '20 at 10:31

The problem was that you compared the second input with itself. You could insert LDA first just before SUB second, but if you invert the output blocks, you can avoid that extra LDA

It is also confusing that you have a label "secondBig", when in fact you are not looking for the biggest number, but the smallest

Correction:

#input: 4 7
           INP
           STA first
           INP
           STA second

           SUB first
           BRP firstLeast

           LDA second     
           OUT
           BRA endProgram
           
firstLeast LDA first
           OUT
           
endProgram HLT

first      DAT
second     DAT

<script src="https://cdn.jsdelivr.net/gh/trincot/lmc@v0.7/lmc.js"></script>

Design an algorithm to input 2 numbers and then output the lowest number in little man computing

3 Answers3