Drink Manager Diagram Maker

If you want to create quick little diagrams like the one above I can strongly recommend PlantUML. Below is the text description that I wrote for the diagram above.

@startuml
title RFID Reader Device Operation

start

:RFID Card ID received;

:Check if Card ID Exists in Internal List;

if (Card Found?) then (Yes)
    :Turn on RED Light;
else (No)
    :Turn on GREEN Light;
    :Add Card ID to Internal List;
endif

stop

@enduml

PlantUML can create all kinds of diagrams. It is free to use online (although the popup adverts are really annoying) but you can also install a local copy.