help with little man computer

trying to write a program for school. the program is supposed to do the following:

Write a program that takes an input value (for example, a number 5). The output should be sum of all numbers from 1 to the value input by the user (in this example, the output would be 1+2+3+4+5 i.e. 15)

what I dont get is how if say I enter 20 how to get it to know that I entered 20 and just add all the numbers from 1 to 20 like count. would I use the SUB (subtract) command to aid in this? help-I'm stuck!!

INP
STA NUM1
LDA NUM1
INP
STA NUM2
LDA NUM2
ADD NUM2
OUT
HLT

 

What language ? assembly?
pseudo code or basic..

input "number?"; N
For Loop = 1 to N
Cnt = Cnt + Loop
Next loop
Print cnt

You have to loop and add the loop count to the number of times the loop has executed.

 

Your code has 2 inputs, but I guess you are trying to make the addition routine into a loop... I would start over making new code, because you will need to plan around a loop.

Similar to what you were thinking and what Foogoo illustrated, you can allocate one box to store the number (LOOP) and another to store the total (CNT), then subtract one from LOOP and add the resulting number to CNT. Jump back to the subtraction unless LOOP<1. At the end of that, OUT CNT would give the result.

 

I didn't know such machines still existed today (http://en.wikipedia.org/wiki/Little_man_computer)!

 

Anyway, you will need to form a loop, similar to what foogoo demonstrated, probably using the BRP instruction.

 

It never existed for practicality, just as a teaching tool. You can actually set one up using yourself as the "little man" to better learn how computers work.

Also, in case the OP didn't catch my mental exercise, "unless LOOP<1" means the same as "if LOOP>=1" in integer math, so pwillener's suggestion and mine are in agreement. I might have been too confusing with that part, but I don't like just giving answers.