Live in a country where tipping is practically unheard of. Lately pay terminals have started appearing in restaurants that have asking for tip enabled by default, and restaurants often don't know how to disable it.

Well, at least there are some safeguards. I was handed the terminal so I put in my PIN code, not realising it was actually asking for a tip. I was pretty confused when it said "value too high" or something like that.

I, an American, was ashamed when I had to ask that a tip be removed from my bill at a restaurant in Camden.

CAMDEN WAS SUPPOSED TO BE WOKE AND Y'ALL FUCKING DOG OVER HERE

Pay your damn staff a good wage

In most places even if you tip cash they are supposed to keep that for the tip pool and it is split. Often among the cook staff and other people at the restaurant.

Hi!

I want to know what it says under 30%.

Please write this code and I'll do it ~~tomorrow~~ when stuff opens today.

No negative sign on the keyboard. But you can enter 2147483647

Assuming the accounting system this thing links with both does not protect from SQL injection attacks (many don't, despite it being easy to protect against) and also has a table named "Bills" with a field named "amount"; what this would do is go through every single Bills record and half the value in the amount field. This would completely fuck the system, particularly when it came to billing and tax filing as the numbers for accounts billing and receivable wouldn't even come close to matching each other. The accounting department would have a hell of a time fixing the damage.

its an sql injection attack.
its rather unlikely that it works in a modern app.

assuming this would work,
it injects a command in the sql database.

it is assumed that the app runs a sql querry with the input field as a parameter e.g.
INSERT INTO "bills" (item, ammount, tip) VALUES ("steak", "20,00 $", "content of the custom tip goes here");

the semicolon indicates the end of the querry,
so the the text would cause the app to run an unfinished querry, and then start a new querry that messes up the content of the bills table.

Nothing. For one, it won't let you enter letters. Two, the table structure to these POS systems are more nuanced than a simple bills table with am amounts field.

It's amusing and all, but it's not something you can do.

Source: work with, and develop around, these types of POS systems.

Amount/0

Negative tip value.

Eventually people will say that about the current options lol.

There should be no default percent options at all. None.

'complete transaction' or 'add optional tip'.

F12 lol. The only issue with a dev console helping would be serverside checking

In my country, we can buy pre-paid credit cards in the supermarket using cash. I guess that is still traceable using supermarket security cameras and facial recognition, but if you're attempting this, I'd make it as difficult as possible.