I'm having problems deciding how to program a certain function, maybe you can help:

As part of a class assignment, I have to program a function that takes in integers from the user until a zero is entered.

Then the function calculates and displays the sum of all positive integers entered, but only the ones that have their digits in increasing order from left to right(for example, 123 is okay, but not 321 or 801).

I don't know how to create a function that decides if an integer's digits are increasing or not.

Take into account that this is a first course in C and this is the first exercise we received, so there are many things I can't use, such as: arrays, pointers, anything more advanced than the last two which I haven't heard of (and thus not listing explicitly) and anything outside of stdio.h.

Any help would be greatly appreciated.

p.s.

The function is called without (so I decided, it wasn't specified. It also wasn't specified it must be a seperate function) any arguments.

It then requests arguments from the user, which it uses for it's calculations.